YLCE-2021 is a cycloaliphatic epoxy resin with two internal epoxy groups, an EEW of 125–135 g/eq and a viscosity of 200–300 mPa·s at 25 °C. Total chlorine is capped at 50 ppm and the cured ester network reaches a published Tg of up to 195 °C. Clear castings and UV-curable coatings are the main uses. Figure 1. YLCE-2021 as delivered, 200–300 mPa·s at 25 °C. The bench reads through the beaker, which is the first test most receiving bays apply. 1. Introduction Alicyclic diepoxides sit apart from the bisphenol A family. YLCE-2021 carries two epoxy groups fused into cyclohexane rings and bridged by an ester link, so the reactive site is the ring, not a glycidyl ether tail. That difference decides where the grade earns its price. An aromatic ring absorbs ultraviolet light and oxidises into coloured products; a saturated ring does not. Clear coatings start from alicyclic stock when colour drift matters. This report fixes the published window, converts epoxide equivalent into hardener weight, and compares the grade with a glycidyl ester and a bisphenol A liquid. It also names the jobs the resin cannot do. 2. Materials and Methods: Test Basis for Cycloaliphatic Epoxy Resin Data 2.1 Product identification and published specification Table 1 holds the identity fields a purchase order needs. Table 2 holds the specification lines the supplier publishes, next to the fields left blank. Table 1. Identity data for YLCE-2021 as published on the product page, accessed 2026-11-12. Item YLCE-2021 Chemical name 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate CAS number 2386-87-0 Epoxide groups 2, both internal (alicyclic) Appearance Colourless liquid Packaging Drums; IBC tanks Shelf life 24 months from manufacture Storage 5–30 °C, dry, out of sunlight Table 2. Published specification of the YLCE-2021 grade, with the test basis normally applied. Item Published value Usual test basis Colour, Pt-Co Max. 50 ASTM D1544 Epoxy equivalent weight 125–135 g/eq ASTM D1652 or ISO 3001 Viscosity at 25 °C 200–300 mPa·s Rotational spindle; ASTM D445 for kinematic Total chlorine Max. 50 ppm Combustion and titration, method not stated Tg of cured casting up to 195 °C Supplier statement, method not stated Density Not published Request on TDS Water content Not published ASTM E203, Karl Fischer Flash point Not published ASTM D93 Three fields formulators ask for early are missing. None changes the stoichiometry, but density decides whether a 200 L batch fills the mould, and water above 0.05% slows a cationic cure. 2.2 Test methods and data source Every value in Table 2 was read from the product page on 2026-11-12. The page does not name the titration behind the 125–135 g/eq window, so the window is a purchase specification, not one measurement. Viscosity carries more uncertainty than a datasheet suggests. A 250 mPa·s liquid sits low on most spindles, where geometry and shear rate move the reading by several percent; duplicate runs agree only at a held 25 °C.Calculated values come from the named structure and the published EEW. Field figures are labelled as such. A purchase decision should rest on a triplicate titration from the lot COA. 3. Results and Discussion: Structure, Reactivity and Alternatives 3.1 Structure and reactivity The named structure gives 252.31 g/mol for C14H20O4 and two epoxides, so the theoretical EEW is 126.2 g/eq. The published 125–135 g/eq window brackets that figure: the grade is close to a pure diepoxide. Epoxy content follows at 0.74–0.80 eq per 100 g, against 0.53 eq per 100 g for a 187 g/eq bisphenol A liquid. That is 45% more reactive groups per kilogram, which is how a tight network forms at 250 mPa·s. The internal epoxide also changes cure chemistry. Ring-opening runs through a cationic path, so strong acids and photogenerated acids start it fast under heat or ultraviolet light. Anhydrides need heat; aliphatic amines barely react. Chlorine separates this grade from glycidyl ethers. Total chlorine is capped at 50 ppm, while the bisphenol A liquid YLE-128 permits 500 ppm hydrolyzable chlorine. Under humid bias, mobile chloride feeds ionic migration, so the cap matters in encapsulation. Treat the 195 °C figure with care. Published Tg tracks the hardener and the schedule, and a casting held 2 h at 120 °C will miss a post-cured value. Confirm it by DMA on your own coupon. 3.2 Comparison with alternative systems Table 3 sets the grade against the two resins a buyer usually shortlists. Table 3. Cycloaliphatic epoxy resin YLCE-2021 against YLCE-186 glycidyl ester and bisphenol A liquid grades. Property YLCE-2021 YLCE-186 YLE-128 Epoxide type Alicyclic, ester bridge 1 alicyclic + 2 glycidyl ester Glycidyl ether Functionality 2 3 2 EEW, g/eq 125–135 100–125 (186 / 186C) 184–190 Viscosity, 25 °C 200–300 mPa·s 2,000–5,000 cps 11,000–15,000 mPa·s Chlorine ≤50 ppm total Not published ≤500 ppm hydrolyzable Colour Pt-Co ≤50 APHA ≤50 Not published State Colourless liquid Colourless to light yellow Clear liquid YLCE-186 reacts faster with anhydrides, because two glycidyl esters join the alicyclic ring, but its viscosity runs eight to twenty times higher. YLE-128 costs less per kilogram and brings adhesion. Read the columns as a process decision. Low viscosity buys filler loading; ester groups buy reactivity; aromatic rings buy toughness and price. None wins on all three. 4. Formulation and Dosage Calculation Hardener weight follows from the epoxide equivalent: phr = 100 × AEW ÷ EEW, where AEW is the active hydrogen equivalent weight. A factor k of 0.80–0.90 is usual for anhydrides, and 0.85 suits MHHPA hardener in castings. Table 4. Hardener demand across the published EEW window, calculated with MHHPA (AEW 168.19 g/eq) and DETA (AHEW 20.6 g/eq). EEW, g/eq Epoxy content, eq/100 g MHHPA, k = 1.00 MHHPA, k = 0.85 DETA, phr 125 0.80 134.6 phr 114.4 phr 16.5 130 0.77 129.4 phr 110.0 phr 15.8 135 0.74 124.6 phr 105.9 phr 15.3 Worked example at the mid-point: EEW 130 g/eq with MHHPA at 168.19 g/eq gives 129.4 phr at k = 1.00, or 110.0 phr at k = 0.85. A 500 g batch therefore takes 550 g of anhydride. Amine hardeners look cheap on paper and behave badly here. DETA at 15.8 phr is stoichiometrically correct, yet the internal epoxide reacts slowly at room temperature and the film stays tacky for hours. A polyetheramine such as YLH-6005 curing agent at 73.1 phr cures, but only with heat. Table 5. Viscosity and EEW of YLCE-2021 blended with bisphenol A liquid, estimated by the log-mixing rule at 25 °C. YLE-128 share Blend EEW Viscosity estimate Practical effect 0% 130 g/eq 250 mPa·s fastest wet-out 10% 134 g/eq 370 mPa·s slight toughening 20% 138 g/eq 550 mPa·s better adhesion to metal 30% 143 g/eq 820 mPa·s cheaper, slower flow These are log-mixing estimates, not measurements. The trade-off is plain: 10% bisphenol A costs 50% more viscosity, and that is about all a casting shop absorbs. 5. Processing Notes and Operating Window Five habits keep a 250 mPa·s casting out of trouble. • Hold the drum at 20–25 °C; at 15 °C viscosity doubles and de-airing drags. • Meter anhydride by weight; density differences skew phr by 5%. • Degas at 5–10 mbar for 10–15 min, in a shallow layer. • Pre-heat the mould; a cold wall traps air at the surface. • Dose 1–3 phr of cationic photoinitiator for UV work, and expect oxygen inhibition. Figure 2. Pouring YLCE-2021 into an open mould. At 200–300 mPa·s the stream breaks cleanly and finds fine detail without vacuum. Cationic cure is easily poisoned. Trace amine from an earlier batch, silicone release agent, or water above 0.05% will slow or stop it. The symptom is a tacky skin over a hard body: it reads as undercure and is contamination. 6. Applications Table 6 ties each published use to the property that carries it. Table 6. Published applications of YLCE-2021 and the property each one depends on. Application Function of the resin Property that decides it Electrical casting Insulation and mechanical support Low viscosity fills fine windings LED packaging Optical path and protection Pt-Co ≤50, no aromatic ring Light-curing coating Fast ambient cure Cationic ring-opening under UV 3D printing resin Photopolymer backbone Low viscosity at 25 °C Cable core composite Binder with low void content Wet-out at low pressure Insulation material Dielectric support, UV stability Saturated ring; UV and radiation resistance Figure 3. A cured YLCE-2021 casting around a threaded insert. Clarity of this order needs a filtered mix and a mould at cure temperature. Two of those uses pull in opposite directions. Optical potting wants the lowest colour, electrical casting the lowest chlorine, and both point at one grade, so a single drum serves both lines. The YLSE-721 amine epoxy covers 200–260 °C structural work. 7. Limitations and Material Verification 7.1 Known limitations and non-applicable cases YLCE-2021 is the wrong choice in four situations, and each shows up in the first trial. • Room-temperature amine cure: the internal epoxide reacts slowly, so a DETA system stays soft overnight. • Hot caustic or strong acid service: the ester bridge hydrolyses before the part visibly discolours. • Thick sections in one shot: low viscosity plus high exotherm can crack a 50 mm block. • High fracture toughness: the tight saturated network is brittle, so blend it or move to an aromatic system. 7.2 Incoming inspection, packaging and safety Incoming inspection covers EEW, total chlorine and colour. EEW by titration according to ASTM D1652 catches a blended or aged drum; chlorine above 50 ppm matters for electrical work; colour drift points to oxidation. The grade ships in drums and IBC tanks and keeps 24 months between 5 and 30 °C, away from sunlight, oxidants and acids. Handling data sits in the MSDS, lot values in the COA. Values here describe the grade, not one drum. 8. Frequently Asked Questions Is YLCE-2021 a glycidyl ether or an alicyclic epoxy? Alicyclic. Both epoxy groups sit inside cyclohexane rings joined by an ester bridge, so no glycidyl ether tail is present and total chlorine stays at or below 50 ppm. Which hardener works with a cycloaliphatic epoxy resin like YLCE-2021? Anhydrides and cationic initiators. MHHPA runs 106–135 phr across the EEW window, and a photoacid serves UV cure. Aliphatic amines react too slowly at room temperature. Why does a UV-cured YLCE-2021 film stay tacky? Water, amine contamination or oxygen inhibition. Dry the resin below 0.05% water, clean the mixer between product families, and cure under nitrogen if the surface must come out hard. Can YLCE-2021 be blended with bisphenol A resin? Up to about 30% by weight. Expect 370 mPa·s at 10% and 820 mPa·s at 30%, with blend EEW rising from 130 to 143 g/eq. What pot life does an YLCE-2021 and MHHPA system give? Several days at 25 °C and weeks at 5 °C. The mix stays latent until roughly 120 °C, which suits one-shot casting. How should YLCE-2021 be stored, and how long does it keep? Sealed between 5 and 30 °C, out of sunlight, 24 months from manufacture. A drum opened repeatedly picks up moisture, so purge the headspace with dry air before closing it. 9. Conclusions YLCE-2021 is a low-viscosity alicyclic diepoxide: 125–135 g/eq, 200–300 mPa·s at 25 °C, 50 ppm total chlorine, and a colourless body that resists yellowing under UV. Stoichiometry is the easy part. MHHPA at 110 phr covers the mid-point EEW, DETA at 15.8 phr works only in an oven, and 10% bisphenol A is about all the flow window takes. Cure chemistry is the hard part. Cationic systems fail on trace moisture and amine, and the failure looks like a tacky skin. Cast a coupon before the production mould is cut. 10. References 1. Yolatech product page, YLCE-2021: https://www.yolatech.com/34-epoxycyclohexylmethyl-ylce-2021-cas-2386-87-0 2. Yolatech product page, YLCE-186: https://www.yolatech.com/45-epoxytetrahydrophthalic-acid-diglycidylester-ylse-186-cas-25293-64-5 3. Yolatech product page, bisphenol A grades: https://www.yolatech.com/bisphenol-a-epoxy-resin 4. Yolatech product page, MHHPA: https://www.yolatech.com/34-methyl-hexahydrophthalic-anhydride-cas-no-25550-51-0-mhhpa 5. Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis (COA) for YLCE-2021, CAS 2386-87-0, Yolatech (available on request). 6. ASTM D1652, epoxy content of epoxy resins; ISO 3001, determination of epoxy equivalent. 7. ASTM D445, kinematic viscosity; ASTM D1544, Gardner color; ASTM E203, water by Karl Fischer; ASTM D93, flash point by Pensky-Martens.

Trifunctional glycidylamine epoxy resin YLSE-0500 is a low-viscosity triglycidyl p-aminophenol liquid at EEW 95-105 g/eq, CAS 5026-74-4. Two siblings, YLSE-0510 and YLSE-0510L, reach 400-1,000 cps at 25 °C. Flow fills fine windings and thin sections, and that same reactivity can char a 5 kg casting. Figure 1. YLSE-0510 in the beaker and a cured disc from the same lot. Colour and thin flow are what buyers check first; neither predicts a 5 kg mould. 1. Introduction All three grades share one molecule: N,N-diglycidyl-4-glycidyloxyaniline, a triglycidyl ether of p-aminophenol with two glycidyl groups on the nitrogen and one on the phenolic oxygen. A bisphenol A liquid carries 2.0. Low viscosity is why buyers pick this family: YLSE-0510 pours at 400-900 cps, so it wets glass roving and copper inserts without solvent. The cost appears after demoulding, when castings crack at inserts and cores char. 2. Materials and Methods: Specification Basis for Trifunctional Glycidylamine Epoxy Resin 2.1 Product identification and published specification One chemistry at three viscosity bands, so one identity table covers all three. Table 1. Identity data for YLSE-0500, YLSE-0510 and YLSE-0510L as published, accessed 2026-11-13. Item YLSE-0500 / 0510 / 0510L Chemical name N,N-diglycidyl-4-glycidyloxyaniline CAS number 5026-74-4 Epoxide groups 3 (trifunctional) Molecular formula C15H19NO4 (calculated, 277.32 g/mol) Package Drum Shelf life At least 12 months, original closed drum, ambient Table 2 repeats the parameter block as printed; a dash means empty. Table 2. Published parameters for YLSE-0500, YLSE-0510 and YLSE-0510L, accessed 2026-11-13. Property YLSE-0500 YLSE-0510 YLSE-0510L Appearance Brown liquid Yellow liquid Yellow liquid EEW, g/eq 95-105 93-106 95-105 Viscosity, cps at 25 °C 1,500-6,000 400-900 500-1,000 Volatiles, % Max. 1.5 Max. 1.0 Max. 1.0 Total chlorine, ppm - - Max. 800 Hydrolyzable chlorine, ppm 2,000 1,000 Max. 200 Epoxy equivalent weight is titrated under ASTM D1652, and each lot carries that value on its certificate. Viscosity is quoted at 25 °C, where a 10 °C fall can double the figure. 2.2 Test methods and data sources Two sources feed this report: the published pages and arithmetic. EEW windows, viscosities and chlorine limits are quoted as printed; molecular weight and hardener weights are calculated and labelled as such. The theoretical EEW of 92.4 g/eq is 277.32 g/mol divided by three epoxide groups. Published windows sit above it because lots carry a few percent of higher oligomers. Duplicate titration is normal; treat one reading as provisional. 3. Results and Discussion: Failure Modes of Trifunctional Glycidylamine Epoxy Resin 3.1 Structure, enthalpy and what follows Three epoxide groups in 277 g/mol give about 10.5 eq/kg, against 5.3 eq/kg at EEW 188. Double the sites, double the heat. Ring opening of a glycidyl ether by an amine releases about 105 kJ/mol, so a kilogram of YLSE-0500 carries near 1,050 kJ. At 1.7 kJ/kg·K, an adiabatic core would pass 500 °C. Geometry decides. A 100 g cup in a 25 °C room sheds heat through the wall. A 5 kg block in a steel mould keeps it, so charring starts at the core. The aniline nitrogen also accelerates the reaction, so the resin gels sooner than 400 cps suggests. Gel time shortens as the shop warms, and not linearly. Table 3. Field symptoms, causes and countermeasures for YLSE-0500, YLSE-0510 and YLSE-0510L castings. Symptom Cause Countermeasure Smoke, dark core Exotherm above 2 kg with a fast aliphatic amine Cap batch mass, chill the mould, or use an anhydride Cracks at inserts Shrinkage stress locked in by fast gel Stage the cure, pre-warm inserts to 60 °C Tg below 200 °C Hardener dosed from the datasheet midpoint Recalculate phr, post-cure 2 h at 160 °C Bubbles, pinholes 1.5% volatiles plus air held by a 400 cps liquid Degas 10-15 min at 5 mbar Leakage current rise 2,000 ppm hydrolyzable chlorine in a DC field Move the part to YLSE-0510L at 200 ppm Brown resin rejected The 0500 grade is brown by specification Judge against the grade descriptor Gel in the line Pot life collapsed at 35 °C ambient Hold at 25-30 °C, meter on demand Two rows of Table 3 are grade-selection problems, not process problems. Chlorine and colour cannot be degassed, filtered or post-cured out of a part. 3.2 Comparison with alternative systems The closest alternative is YLSE-0600, the 3-isomer of the same molecule, at 10,000-25,000 cps: same formula, fifty times the viscosity. Table 4. Property comparison, with EEW-derived heats for ranking only: YLSE-0500 family against YLSE-0600, YLSE-721 and a bisphenol A liquid. Property YLSE-0500 family YLSE-0600 YLSE-721 YLE-128 Epoxide groups 3 3 4 2 EEW, g/eq 93-106 100-110 105-125 184-190 Viscosity at 25 °C, cps 400-6,000 10,000-25,000 3,000-7,000 11,000-15,000 Hydrolyzable chlorine, ppm 200-2,000 Not published Not published Max. 500 Heat per kg at full cure About 1,050 kJ About 980 kJ About 830 kJ About 540 kJ Typical role Casting, RTM, winding Adhesive, laminating Aerospace composites General purpose Pick YLSE-0600 when the resin must stay put, and 0500 or 0510 when it must flow into a closed mould. Their EEW windows overlap, so viscosity settles it. 4. Formulation and Dosage Calculation Hardener weight follows one line: phr = 100 × AHEW ÷ EEW. Stoichiometry failures start with dosing from the EEW midpoint instead of the lot certificate. Table 5. Hardener demand per 100 g of resin at three EEW points inside the published window. Hardener AHEW, g/eq phr at EEW 95 phr at EEW 100 phr at EEW 106 Diethylenetriamine, theoretical 20.6 21.7 20.6 19.4 YLH-6005 polyetheramine 95 100.0 95.0 89.6 MHHPA anhydride, k = 0.85 142.96 150.5 143.0 134.9 Worked example. A 20 kg batch of YLSE-0500 arrives at 104 g/eq. Against YLH-6005 at AHEW 95 the correct addition is 91.3 phr, or 18.26 kg. The nominal 100 g/eq gives 95.0 phr, or 19.0 kg, so the gap is 0.74 kg and 4% excess amine. Surplus amine plasticises the network, lowers Tg and raises water uptake. A 4% surplus can pull a 200 °C system into the 180s, and the drop gets blamed on the resin. Anhydrides invert the arithmetic. MHHPA carries 168.19 g/eq, and practice applies 0.85 of that, giving 143 phr at EEW 100. The heavy addition is why anhydride casting runs at 80-100 °C. 5. Processing Notes and Operating Window Four settings keep it workable: batch mass, resin temperature, vacuum, and cure ramp. • Cap batches at 2 kg with an aliphatic amine at 25 °C, and halve that above 30 °C. • Hold resin at 25-30 °C. Warming to 40 °C halves pot life unless the section is under 3 mm. • Degas at 5 mbar for 10-15 minutes. The 1.5% volatile limit on YLSE-0500 makes the step non-optional. • If the system is aromatic-amine and aimed at the 200 °C class, ramp to 80 °C, hold 2 h, then post-cure 2 h at 160 °C. Figure 2. Degassing a YLSE-0510 mix at 5 mbar. Foam rises, collapses, then the resin clears from the centre outwards. Bubbles that survive degassing usually come from the hardener. Polyetheramine takes up water in an open drum, and 0.5% water there foams a casting that looked clear in the cup. 6. Applications The published list runs from electrical casting to composite winding; grade choice follows chlorine and viscosity. Table 6. Grade selection by application and process. Application Process Grade Reason HV bushings, insulators APG, vacuum casting YLSE-0510L 200 ppm hydrolyzable chlorine Micro-motor sealing Vacuum casting YLSE-0510 400-900 cps wets fine wire Carbon fibre winding Filament winding YLSE-0510 Low drag through the bath RTM and VARTM panels Resin injection YLSE-0510 Fills a 2 m flow path at 25 °C High-temperature adhesive Hand mix, bonded joint YLSE-0500 1,500-6,000 cps stays on the bondline Reactive diluent Blend at 5-15 phr YLSE-0510L Trifunctional, so Tg retention beats BGE Figure 3. A cast insulator plate with brass inserts, moulded from YLSE-0510L. Shrinkage stress concentrates at the bosses, where the cure ramp matters more than the mix ratio. For high-voltage parts the 200 ppm figure matters more than viscosity. Ionic chlorine migrates under a DC field in humid air, so leakage current appears months after the part passed its test. 7. Limitations and Material Verification 7.1 Known limitations and unsuitable cases The 200 °C glass transition figure is a class statement for post-cured systems, not a measured value. The product URL still reads 44-methylenebisnn-diglycidylaniline while the page describes the triglycidyl p-aminophenol grades, so order by CAS. Grade windows differ inside one family, 93-106 g/eq across the three, so the lot certificate decides. Chlorine is the other constraint. At 2,000 ppm, hydrolyzable chlorine rules YLSE-0500 out of high-voltage insulation, while YLSE-0510L caps that at 200. The pages print no Gardner number; appearance is brown for YLSE-0500 and yellow for the other two, so a dark drum is specification, not age. Do not run unfilled sections above 5 kg with an aliphatic amine, or specify YLSE-0510 where the drawing names a chlorine ceiling under 200 ppm. 7.2 Incoming verification, packaging and storage Checks for every drum: EEW by titration with n = 3, viscosity at 25 °C, and water by Karl Fischer according to ASTM E203. Chlorine matters only for electrical parts, and then on every lot. Viscosity is measured at 25 °C under ASTM D445, and colour, where quoted, under ASTM D1544. If a drum titrates at 104 g/eq it still sits inside the YLSE-0510 window, and the dosage follows the titration. Storage runs 12 months from manufacture in the closed original drum. Resin from a warm warehouse still titrates in window, and still gels faster. Safety data comes from the MSDS, limits from the TDS. Skin contact is the routine risk with glycidyl ethers, and gloves rated for epoxy beat nitrile examination gloves. 8. Frequently Asked Questions What separates YLSE-0500, YLSE-0510 and YLSE-0510L? Viscosity and chlorine. YLSE-0500 pours at 1,500-6,000 cps with 2,000 ppm hydrolyzable chlorine, YLSE-0510 at 400-900 cps with 1,000 ppm, YLSE-0510L at 500-1,000 cps with 200 ppm. Why did my casting crack the day after demoulding? Fast gel at high crosslink density locks shrinkage stress into the part, and it concentrates at inserts. Stage the cure, pre-warm inserts, and hold the part at 60 °C before the post-cure ramp. Can YLSE-0500 be cured at room temperature with DETA? In thin sections, yes. Above about 2 kg the exotherm outruns the mould, and the core chars while the surface still looks sound. Chill the mould or move to an anhydride above that mass. Why is the measured Tg below the 200 °C class figure? Check two things first: whether the hardener weight came from the lot EEW, and whether the post-cure reached 160 °C in the core. Both give the same 20-40 °C shortfall. Is YLSE-0510L suitable for high-voltage insulation? It is the grade intended for that duty, at 200 ppm hydrolyzable chlorine. Suitability still depends on the cured system, the design field and the applicable standard; a low chlorine figure is not a certification. Can these grades work as reactive diluents? Yes, at 5-15 phr in a bisphenol A or phenolic system. Trifunctional dilution costs less Tg than butyl ether and more per kilogram, so the trade-off is thickness against budget. 9. Conclusions YLSE-0500, YLSE-0510 and YLSE-0510L are one triglycidyl p-aminophenol molecule at three viscosity and purity bands, and the band decides the application. Cure enthalpy near 1,050 kJ/kg sits behind most field failures here. Mass limits, a staged cure and lot-specific hardener weights address it; extra degassing does not. Chlorine rather than viscosity separates 0510L from 0510, and 200 ppm against 2,000 ppm is a factor of ten. Take EEW from the certificate: on a 20 kg batch the midpoint habit costs 0.74 kg of hardener. 10. References 1. Yolatech, N,N-diglycidyl-4-glycidyloxyaniline YLSE-0500 / 0510 / 0510L, https://www.yolatech.com/44-methylenebisnn-diglycidylaniline (accessed 2026-11-13). 2. Yolatech, 3-glycidyloxy-N,N-diglycidylaniline YLSE-0600, https://www.yolatech.com/3-glycidyloxy-nn-diglycidylaniline-ylse-0600-afg-90m-cas-71604-74-5 (accessed 2026-11-13). 3. Yolatech, 4,4'-methylenebis(N,N-diglycidylaniline) YLSE-721, https://www.yolatech.com/44-methylenebisnn-diglycidylaniline-ylse-721721c721l (accessed 2026-11-13). 4. Yolatech Technical Data Sheet (TDS) and Certificate of Analysis (COA) for YLSE-0500, YLSE-0510 and YLSE-0510L, CAS 5026-74-4. 5. ASTM D1652, epoxy content of epoxy resins; ISO 3001, epoxide equivalent. 6. ASTM E203, water by Karl Fischer titration; ASTM D445, kinematic viscosity; ASTM D1544, Gardner colour. 7. Yolatech, bisphenol A epoxy resin grade table, https://www.yolatech.com/bisphenol-a-epoxy-resin (accessed 2026-11-13).

Phenolic epoxy resin viscosity is a flow property that separates YLEP-631 from YLEP-638. YLEP-631 is a liquid measuring 1,100-1,700 mPa·s at 52 °C; YLEP-638 is semi-solid, with a 36-40 °C softening point. Their EEW windows overlap at 168-190 g/eq, so flow decides the grade. Both are packed in drums. Figure 1. A wrapped pallet of YLEP-631 drums. The label carries the lot number, net and gross weight, and the wrap keeps moisture out until the melt station. 1. Introduction Both grades are phenol-formaldehyde novolac resins glycidylated with epichlorohydrin, and both carry the same five-line application list. Choosing between them is a rheology decision, not a chemistry one. Viscosity governs how resin reaches fibre or fills a cavity. Too thick and the laminate keeps dry spots; too thin and the varnish drains before the press closes. Neither defect shows up on a certificate of analysis. This report compares the two specifications, derives what overlapping EEW windows do to hardener weight, and states which process window each grade serves. Values come from the product pages read on 2026-11-06 and from published industry data. 2. Materials and Methods: Test Basis for Phenolic Epoxy Resin Viscosity 2.1 Product identification and published specification Table 1 collects identity data and the open fields. Neither grade publishes a CAS number; only YLEP-631 publishes an epoxide count. Table 1. Identity data for YLEP-631 and YLEP-638 as published, accessed 2026-11-06. Item YLEP-631 YLEP-638 CAS number Not published Not published Epoxide groups 2.7 average Not published Appearance Colorless to yellowish liquid Liquid in table, semi-solid in text Package Drum Drum Shelf life At least 12 months At least 12 months Table 2 lists the rows that differ. The rest of the two pages is identical text, so the specification alone cannot settle a choice. Table 2. Published specification of YLEP-631 and YLEP-638. Property YLEP-631 YLEP-638 EEW 168-180 g/eq 170-190 g/eq Color, Gardner 3 maximum 3.0 maximum Hydrolyzable chlorine 500 ppm maximum 500 ppm maximum Flow property 1,100-1,700 mPa·s at 52 °C Softening point 36-40 °C Method named Temperature only None 2.2 Test methods and data sources Epoxy equivalent weight is determined by titration, and the lot COA outranks the catalogue window. ASTM D1652 and ISO 3001 describe the two routes. YLEP-631 viscosity is measured at 52 °C, the only flow number published. ASTM D445 covers the kinematic route; a rotational reading can sit a few hundred mPa·s away. Softening point is a ring-and-ball figure in European specifications, and the YLEP-638 page names no method. A drop-point result reads about 10 °C higher on the same sample. Incoming checks run in duplicate, with a third determination from another drum position when results disagree by more than 5 g/eq. No independent laboratory work was performed; every figure is published or arithmetic on one. 3. Results and Discussion: What Controls Phenolic Epoxy Resin Viscosity 3.1 Backbone, molecular weight and softening point Molecular weight distribution sets the flow gap, not the epoxide count. A novolac oligomer mixture carries a spread of chain lengths, and the long tail lifts softening point faster than average EEW. YLEP-631 averages 2.7 epoxy groups per molecule against two for a bisphenol A diglycidyl ether. That functionality explains the denser cured network; it does not explain the flow. Table 3. Softening point against melt viscosity at 150 °C for cresol novolac grades, published industry data. Softening point, °C Melt viscosity, Pa·s Ratio to 55 °C row 55 0.1 1.0 67 0.3 3.0 70 0.5 5.0 73 0.6 6.0 80 1.0 10.0 88 1.7 17.0 Across the 33 °C span of that table, melt viscosity rises 17-fold, about 2.4 times per 10 °C. That factor is calculated from the published pairs, and it is why a 4 °C band is worth arguing about. YLEP-638 sits at 36-40 °C, below the lowest row. Read against the curve, it is a solid that softens in a warm room and flows at 80 °C, which matches a melt tank rather than a drum pump. 3.2 Comparison with alternative systems A bisphenol A liquid is the default alternative, and the EEW overlap hides how differently the families behave. Table 4. Property comparison of the two novolac grades against bisphenol A epoxy resin. Property YLEP-631 YLEP-638 Bisphenol A liquid EEW 168-180 g/eq 170-190 g/eq 184-190 g/eq State at 25 °C Liquid Semi-solid Liquid Flow number 1,100-1,700 mPa·s at 52 °C 36-40 °C softening point 11,000-15,000 mPa·s at 25 °C Epoxide groups 2.7 Not published 2 Hydrolyzable chlorine 500 ppm maximum 500 ppm maximum Grade dependent Stoichiometry barely moves: a 168-190 g/eq window against roughly 184-190 g/eq is a few percent of hardener weight, inside a batch tolerance. Cured heat resistance does move. Crosslink density from 2.7 epoxides against two keeps modulus higher at 150 °C, and the same density is why elongation falls. For a thin part under 100 °C, the bisphenol A liquid usually wins on cost and toughness. Above that ceiling the novolac earns its price. 4. Formulation and Dosage Calculation Hardener weight follows one equation, phr being parts per hundred parts of resin by mass. phr = 100 × AHEW ÷ EEW A phenol novolac hardener at a 105 g/eq hydroxyl equivalent is a common laminate pairing. The figure is typical rather than universal; check the hardener TDS before freezing a recipe. Table 5. Stoichiometric hardener dosage in phr across the published EEW window, calculated from the equation above. Hardener 168 g/eq 174 g/eq 180 g/eq 190 g/eq Phenol novolac, 105 g/eq 62.5 60.3 58.3 55.3 DDS, 62.1 g/eq 37.0 35.7 34.5 32.7 DICY, 21.0 g/eq 12.5 12.1 11.7 11.1 Blending changes flow without rewriting the recipe. A 70/30 mass blend of YLEP-638 and YLEP-631 lands at 178.2 g/eq and moves the DICY figure from 11.7 to 11.8 phr. Filler loadings are quoted in phr and bought in weight percent. Silica at 250 phr is 71.4% by weight; a 70% target is 233 phr. Past 250 phr a planetary mixer stops wetting out and the job needs a press. 5. Processing Notes and Operating Window The operating window is narrower than the specification suggests: the only published flow number sits at a temperature no workshop holds all day. Warm YLEP-638 to 70-90 °C in a drum heater or melt tank. Below 60 °C the grade resists pumping. Hold YLEP-631 above 45 °C; an ambient pump curve has to be measured, not assumed. Filter the melt at 100 µm before it meets the hardener. Degas a filled mix for 10-15 min at 5 mbar. Air in 250 phr of silica does not travel. Size the batch before trusting a pot life; 5 kg and 50 kg do not share a gel time. Without a melt line, a solution type phenolic epoxy resin avoids the tank, at the cost of solvent recovery. A reactive diluent such as 16-hexanediol diglycidyl ether YLD-6008 cuts viscosity without solvent, but lowers crosslink density and the heat resistance that justified a novolac. Two habits prevent most of the trouble. Keep the melt covered, since a wet novolac foams under vacuum. Log tank temperature every batch; a 10 °C drift moves melt viscosity by about 2.4 times. Figure 2. The YLEP-638 drum label: lot number, manufacture and expiry dates, 220 kg net and 238 kg gross. Log the lot beside the tank temperature. 6. Applications Both pages list five end uses, and the split follows the process rather than the market. Table 6 sets out which grade carries flow. Table 6. Process role of each grade across the five published applications. Application YLEP-631 YLEP-638 Laminates and CCL Varnish at 40-60% solids High-build varnish, needs solvent Potting and casting Carries filler to 250 phr Hot pour above 70 °C Adhesives Metal and ceramic bonds Film and paste, hot applied Coatings Solvent-borne, 30-50% solids High-solids bake Composites Warm RTM and wet winding Prepreg and hot-melt film Laminate work is the clearest case. A varnish on the liquid grade holds 40-60% solids and still passes the tower; the same solids on the semi-solid grade need a stronger solvent. Figure 3. Four drums on one pallet at the loading bay; a casting campaign is usually sized in pallets, not kilos. 7. Limitations and Material Verification 7.1 Known limits and unsuitable processes Ambient hand lay-up suits neither grade. The liquid grade is workable at 52 °C, not at workshop temperature, and the semi-solid must be melted before it wets glass. Nor is either grade an electronic material. A 500 ppm hydrolyzable chlorine ceiling suits laminates; a customer needing single-digit chloride must ask for another grade. Two details need resolution before either grade enters a drawing. Appearance is listed as liquid for YLEP-638 while the text calls it semi-solid; trust the text, since a 36-40 °C softening point implies a solid at ambient. The softening method is unstated, and a drop-point number would read 46-50 °C. No CAS number is published either, so a customs or REACH dossier must rest on the supplier declaration. 7.2 Incoming inspection, packaging and storage Incoming inspection covers three numbers. EEW is determined by titration against the lot COA, alongside Gardner color and hydrolyzable chlorine. Reject a lot outside the EEW window, because every phr in Table 5 shifts with it. Packaging is a drum, with at least 12 months from manufacture in the original packing. A drum reopened repeatedly collects moisture at the headspace; use it first. Storage is the standard routine: ventilated area, away from flame and sunlight, cap closed after use. Safety data sits in the MSDS; both grades are skin sensitisers. Any RoHS, REACH or UL 94 statement has to be verified against current certificates, since nothing in a description implies certification. 8. Frequently Asked Questions Does YLEP-631 drop in for YLEP-638 without reformulation? No. Hardener weight is unchanged, but flow is not: a 168-180 g/eq liquid replaces a 36-40 °C semi-solid, so a melt line becomes a pump line. Reformulate the solvent first. What is the viscosity of YLEP-631 at room temperature? Not published. The only flow number is 1,100-1,700 mPa·s at 52 °C, so a 25 °C pump curve must be measured on your own lot. Why does YLEP-638 thin out faster than expected when warmed? Melt viscosity falls about 2.4 times per 10 °C of softening point. A tank set 15 °C high can halve working viscosity and let the mix drain off a wall. Can the two grades be blended to hit a target softening point? Yes. A 70/30 mass blend lands at 178.2 g/eq and its softening point falls between the components; verify by ring-and-ball rather than by calculation. Which hardener suits a 36-40 °C softening point novolac? DDS at 34.5-37.0 phr or DICY at 11.7-12.5 phr. A phenolic novolac hardener at 55-62 phr gives the highest heat resistance and the shortest pot life. Is 500 ppm hydrolyzable chlorine low enough for electronics? For a laminate, usually. For an encapsulant touching aluminium bond pads, no; ask for a lower-chloride grade and confirm it on the COA. 9. Conclusions YLEP-631 and YLEP-638 share a novolac backbone and overlapping EEW windows, so stoichiometry does not separate them. State does: 1,100-1,700 mPa·s at 52 °C against a 36-40 °C softening point. Hardener demand stays within a few percent either way, 55.3 to 62.5 phr for a phenolic novolac. Flow, filler tolerance and B-stage behaviour are what a process trial has to measure. Pick the liquid grade when the mix must move at moderate temperature, the semi-solid when the part needs a dry stage before cure. Confirm the softening method before the first order. 10. References 1. Yolatech product page, YLEP-631: https://www.yolatech.com/pne-type-phenolic-epoxy-resin-ylep-631 2. Yolatech product page, YLEP-638: https://www.yolatech.com/pne-type-phenolic-epoxy-resin-ylep-638 3. Yolatech product page, bisphenol A grades: https://www.yolatech.com/bisphenol-a-epoxy-resin 4. Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis (COA) for YLEP-631 and YLEP-638, Yolatech (available on request). 5. ASTM D1652, epoxy content of epoxy resins (EEW); ISO 3001, determination of epoxy equivalent. 6. ASTM D445, kinematic viscosity; ASTM D1544, Gardner color; ASTM E203, water by Karl Fischer.

Solution type phenolic epoxy resin is a multifunctional novolac epoxy supplied as an 80% solids solution, in EEW 170-220 g/eq grades on solids. Two grades are listed, YLEP-210-A80 and YLEP-180-K80. Hardener dosage belongs on the solution supplied, not on solids. Dilution adds 25% to the working EEW. Figure 1. Drum supply of an 80% solids phenolic epoxy solution, the form most impregnation lines receive. 1. Introduction Novolac epoxy starts from a phenol-formaldehyde condensate, not from bisphenol A. Epoxidising that condensate gives more than two glycidyl groups per molecule, and the cured network reaches higher crosslink density than a bisphenol A system. Heat, solvent and chemical resistance and dimensional stability rise with that density. Brittleness rises too, and adhesion to copper foil falls. Formulators blend in a bisphenol A resin for toughness and adjust cure for copper grip. Both grades on the product page ship at 80% solids, the form impregnation lines actually buy. That number sits between the datasheet and every downstream figure: hardener weight, bath viscosity, volatile content, cost per equivalent. Values below come from the public solution type phenolic epoxy resin product page, read on 2026-11-06; calculated figures are labelled as such. 2. Materials and Methods: Solution Type Phenolic Epoxy Resin Grades 2.1 Product Identification and Specification Table 1 reproduces both grades as published, without rounding. Table 1. Published specification of the two 80% solids grades, EEW quoted on resin solids. Grade EEW (g/eq) Viscosity (mPa·s) N.V. (%) YLEP-210-A80 200-220 1000-4000 80±1 YLEP-180-K80 170-190 200-500 80±1 No CAS number, formula, solvent identity or functionality is published for either grade; those fields stay open rather than being imported. 2.2 Test Methods and Data Sources EEW for a solution grade is normally determined by titration according to ASTM D1652 or ISO 3001, and quoted per gram of solids. Viscosity is rotational, measured at 25 °C. Colour follows ASTM D1544; water follows ASTM E203. Calculated values carry their formula. Values labelled empirical are practice-based starting points and were not run in triplicate here. Where the page is silent, the text says not published. 3. Results and Discussion 3.1 Structure and Reactivity: Why 80% Solids Moves Dosage Dilution is where dosage errors start. The published 200-220 g/eq describes resin solids, while the drum holds 20% solvent. Per gram of liquid as supplied the equivalent weight becomes 250-275 g/eq, from 200 ÷ 0.80 and 220 ÷ 0.80. YLEP-180-K80 moves the same way, from 170-190 g/eq on solids to 212.5-237.5 g/eq as supplied. Equivalents per kilogram run inverse: 4.00 eq/kg at 250 g/eq, 3.64 eq/kg at 275 g/eq, 4.71 eq/kg for K80 at 212.5 g/eq. A 90% bisphenol A solution such as YLE-128A90 lands at 204-216 g/eq as supplied, which is 4.6-4.9 eq/kg. The phenolic grades therefore deliver fewer equivalents per kilogram of purchased liquid. That gap is paid in freight as well as resin. Substitution on the ring shifts the balance inside the family. CNE grades carry a methyl group ortho to the ether linkage and beat PNE grades on water resistance and melt viscosity, while BNE grades reach a DDS-cured Tg of 224 °C. Neither solution grade states its functionality, and 2.7 epoxy groups per molecule is published only for YLEP-631. 3.2 Comparison with Alternative Systems Table 2 puts both solution grades beside the nearest solid novolac and a standard bisphenol A solution, using published values only. Table 2. Attribute comparison with a solid novolac and a 90% bisphenol A solution. Attribute YLEP-210-A80 YLEP-638 solid YLE-128A90 Delivery form 80% solution Semi-solid 90% solution EEW on solids, g/eq 200-220 170-190 184-194 Solids content, % 80±1 100 90±1 EEW as supplied, g/eq 250-275 170-190 204-216 Viscosity 1000-4000 mPa·s 36-40 °C softening ≤1000 mPa·s Hydrolyzable chlorine Not published ≤500 ppm Not published Epoxy groups per molecule Not published Not published 2 Main use on datasheet Laminate varnish High-temperature laminate General laminating The trade-off sits in two rows. YLEP-638 gives the same novolac backbone at 170-190 g/eq with no solvent to evaporate, but its 36-40 °C softening point forces a melt step and hydrolyzable chlorine is capped at 500 ppm. In practice a plant with a solvent line prefers the solution; one without should stay with flake. Solvent is never free. At a density near 1.05-1.10 kg/L, 20% solvent works out to roughly 210-220 g/L of volatile content. 4. Formulation and Dosage Calculation: phr on the As-Supplied Solution Three equations cover the work. As-supplied EEW equals solids EEW divided by the solids fraction, EEW_s = EEW_solids ÷ (N.V. ÷ 100). Amine demand follows phr = 100 × AHEW ÷ EEW_s, with AHEW at 20.6 g/eq for DETA, 21.0 g/eq for dicyandiamide and 62.1 g/eq for diaminodiphenylsulfone. Table 3. Hardener demand per 100 g of solution, calculated from as-supplied EEW. EEW as supplied (g/eq) DETA, phr DICY, phr DDS, phr 212.5 (K80 low) 9.69 9.88 29.22 237.5 (K80 high) 8.67 8.84 26.15 250 (A80 low) 8.24 8.40 24.84 262.5 (A80 middle) 7.85 8.00 23.66 275 (A80 high) 7.49 7.64 22.58 At 250 g/eq the figures read 8.24 phr of DETA and 8.40 phr of DICY per 100 g of solution. At 275 g/eq they fall to 7.49 and 7.64 phr, a 9% swing across one band. Buy the narrowest band the supplier will commit to, or dose against the COA. The common error is skipping the dilution. Treating YLEP-210-A80 as a 210 g/eq resin gives 9.81 phr of DETA against a correct 8.24 phr, a 19% amine excess that plasticises the network and raises water uptake. If a batch stays tacky, check whether dosage was figured on solids before adding accelerator. Thinning is arithmetic. Per 100 kg of 80% solution there are 80 kg of solids, and the solvent needed to reach a target N.V. is 80 ÷ (target ÷ 100) − 100. Table 4. Solvent addition from 100 kg of 80% solution at 200 g/eq solids. Target N.V. (%) Solvent to add (kg) Final batch (kg) EEW as supplied (g/eq) 75 6.7 106.7 266.7 70 14.3 114.3 285.7 65 23.1 123.1 307.7 60 33.3 133.3 333.3 Blending often beats thinning. Equal masses of the two grades give 2 ÷ (1 ÷ 250 + 1 ÷ 212.5) = 230 g/eq as supplied. Viscosity follows a logarithmic mixing rule, ln η = Σ w ln η, which for 2500 and 350 mPa·s at equal weights predicts about 935 mPa·s. 5. Processing Notes and Operating Window The window is set by solvent loss, not by the resin. • Mix at 30-40 °C; a cold solution traps air that shows up as pinholes. • Hold the bath at 20-25 °C. Every 10 °C of extra heat halves the working life of an accelerated DICY system. • Measure solids on the bath, not only on the drum. N.V. can climb several points in one shift. • Stage the cure: 30 min at 90 °C before gel. Straight to 160 °C blisters the laminate unless the section is thin. • Filter before use; novolac solutions throw a sediment that scorches under a hot press. Figure 2. Impregnation bath running an 80% solids novolac varnish, with solids checked on the bath. Pot life at 25 °C is typically 8-24 h for a DICY varnish and minutes for a DETA mix, so DETA belongs in small batches. A bath left open all afternoon will not behave like the morning sample even at the same N.V. 6. Applications Six applications are listed, and the two grades do not serve them equally. Table 5. Application map for the two grades, from the list on the product page. Application Function of the solution Grade fit Process note Copper-clad laminate Impregnation varnish YLEP-210-A80 Hold N.V. to control flow Electronic laminate Prepreg resin with DICY Both grades Control stage B Heat-resistant adhesive Structural bondline YLEP-210-A80 Cure above 160 °C Heat-resistant coating Baked or ambient film YLEP-180-K80 Low band suits spray Civil engineering Solvent-borne primer YLEP-180-K80 Long open time Electronic ink Vehicle for screen ink YLEP-210-A80 Solvent balance sets levelling Copper-clad laminate takes YLEP-210-A80, where the higher EEW tolerates a stiffer varnish. Spray and primer work takes YLEP-180-K80, whose 200-500 mPa·s band atomises without extra thinning. Figure 3. Heat-resistant coating applied from a thinned solution; the K80 grade sprays at supplied viscosity. 7. Limitations and Material Verification 7.1 Known Limitations and Where These Grades Do Not Fit These are solutions, which rules out several jobs. Solvent-free casting is not one: 20% volatile content boils at gel and leaves voids in a thick section. Neat metal bonding is a poor fit too, because the cured novolac is brittle and grips copper less firmly than bisphenol A. Three fields are unpublished and should be confirmed before a specification is frozen: solvent identity, functionality and hydrolyzable chlorine. Swapping a glycol ether for an aromatic solvent changes water pick-up and evaporation, so check with the supplier before the swap; the press will show blisters otherwise. The EEW basis is the fourth check. If the COA states EEW as supplied, do not divide by 0.80 again; that under-doses hardener by about 20% and leaves a tacky laminate. 7.2 Incoming Inspection, Packaging, Storage and Safety Incoming inspection covers four numbers per lot: EEW by ASTM D1652 or ISO 3001, viscosity by ASTM D445 at 25 °C, colour by ASTM D1544 and water by ASTM E203. Keep a 200 g sample per batch; it settles arguments later when a lot drifts by 3 g/eq. Packaging is drums, with at least 12 months shelf life from manufacture in original packing at ambient temperature. Store ventilated, away from flame and direct sunlight, and close the cap after use: an open drum skins over. Safety information sits in the MSDS and the TDS governs the specification. Confirm handling, labelling and transport classification before shipping, and treat any RoHS or REACH statement as needing documentary confirmation rather than as a granted certification. 8. Frequently Asked Questions What does 80% solids mean for hardener dosage? The labelled EEW is divided by 0.80 before use. YLEP-210-A80 at 200-220 g/eq on solids becomes 250-275 g/eq as supplied, so DETA demand drops from 9.81 to 8.24 phr per 100 g. Can YLEP-210-A80 replace a 100% solids novolac one for one? No. Swapping it for a 170-190 g/eq solid grade removes about a quarter of the reactive mass per kilogram, so the batch needs more resin and less hardener. Which grade suits a copper-clad laminate varnish? YLEP-210-A80 is the usual starting point. Its higher EEW gives a stiffer prepreg, and the 1000-4000 mPa·s band leaves room for a flow promoter. Does the solvent change pot life? Indirectly. Solvent does not react, but it dilutes the reactants and slows the temperature rise, so a thinned mix can look long-lived in the bath and still gel quickly as a thin film. What should the COA report for epoxy equivalent weight? The value, the basis and the method. Ask for EEW in g/eq stating whether it refers to resin solids or to the solution as supplied, plus the titration standard used. Is a 50/50 blend of the two grades practical? Yes, and it is common. The blend lands near 230 g/eq as supplied with viscosity around 935 mPa·s, which suits lines that cannot run the 4000 mPa·s end of YLEP-210-A80. 9. Conclusions Two 80% solids novolac grades cover EEW 170-220 g/eq on solids, which is 212.5-275 g/eq as supplied. Every hardener figure has to be computed on the as-supplied basis; skipping it over-doses amine by 19%. The grades buy heat and solvent resistance with brittleness, lower copper adhesion and 20% volatile content. Where solvent cannot be tolerated, the solid novolac route on the phenolic epoxy resin range page remains correct, and the solution type bisphenol A epoxy resin line covers work needing more equivalents per kilogram. 10. References Yolatech product page: https://www.yolatech.com/solution-type-phenolic-epoxy-resin (accessed 2026-11-06). Technical Data Sheet for YLEP-210-A80 and YLEP-180-K80, 80% solids phenolic epoxy solution (available on request). Certificate of Analysis (COA) for YLEP-210-A80, lot-specific EEW and solids (available on request). ASTM D1652 and ISO 3001, titration routes for the epoxy content of epoxy resins (EEW). ASTM D445, kinematic viscosity; ASTM D1544, Gardner color of transparent liquids. ASTM E203, water content by Karl Fischer titration; ISO 9702, amine group nitrogen content of amine epoxide hardeners.

YLH-6005 is a low viscosity epoxy hardener built on a nonylphenol-free modified polyetheramine with AHEW 95 g/eq and 250–450 cps at 25 °C. It carries 50 phr against an EEW 190 resin, and this report ranks it here against four in-house grades on gel time, colour, hardness build and flexural strength. Figure 1. YLH-6005 as supplied: a light yellow liquid in the 250–450 cps band, the viscosity that keeps a self-levelling floor mix workable. 1. Introduction A contractor choosing between five amine hardeners is choosing which property to give up. YLH-6005 gives up colour and some flexural strength to gain the fastest gel in the low-viscosity group: 23 min against 30 to 50 min. Four modified amine hardeners share the 250–12000 cps envelope and one test reference, a liquid bisphenol A resin of EEW 190, so published numbers read across without extrapolation. Scope stops at ambient cure: flooring and electronic potting. Laminating and anhydride chemistry sit outside. 2. Materials and Methods: Identification and Test Basis 2.1 Product Identification and Published Specification YLH-6005 ships as a light yellow liquid in drums, with at least 12 months of shelf life unopened at ambient. No CAS number is published, so identification depends on the grade name and the lot COA. Table 1. Product identification of YLH-6005 as published by the supplier. Item Detail Grade YLH-6005 Chemistry Modified polyetheramine, nonylphenol-free Appearance Light yellow, transparent liquid CAS number Not published; confirm on the COA Packaging Drum; net weight not published Table 2. Published physical and cure properties of YLH-6005, with the basis behind each number. Property Value Basis Colour, Gardner Max. 3 ASTM D1544 Viscosity at 25 °C 250–450 cps Supplier data AHEW 95 g/eq Supplier data Amine value 270 mg KOH/g ISO 9702 Density at 25 °C 1.02 g/cm3 Supplier data Added weight 50 phr Calculated at EEW 190 Gel time, 100 g at 25 °C 23 min Shop test Thin-film set, 15 g at 3 mm 2.5 h Shop test Shore D 70, 15 g at 3 mm 10 h Shop test Bending strength 82.3 MPa EEW 190 reference One entry is derived, not measured: the 50 phr added weight is 100 × 95 ÷ 190, the stoichiometric ratio for the reference resin, so it tracks resin EEW. 2.2 Test Methods and Data Sources Colour is a Gardner maximum measured at 25 °C per ASTM D1544, and viscosity a 25 °C figure. Resin epoxy content follows ASTM D1652; amine value on an incoming drum is normally determined by ISO 9702. Gel time, thin-film set and Shore D build are shop tests, not cure kinetics. They rest on 100 g of mixed mass and a 15 g film at 3 mm, without a standard deviation or replicates. 3. Results and Discussion: How a Low Viscosity Epoxy Hardener Trades Speed for Strength 3.1 Equivalent Weight Sets the Ratio, Not the Rate AHEW 95 g/eq fixes the stoichiometry: 50 phr against the EEW 190 reference resin, which makes the hardener 33% of the mixed weight. Two grades share that ratio: YLH-6005 at AHEW 95 and YLH-6004 at 96 g/eq. Their gel times differ twofold, 23 min against 50 min, which equivalence cannot explain. Amine value is not a shortcut to AHEW. Dividing 56100 by 270 returns 208 g/eq against a published 95 g/eq, so the two figures sit on different bases. Use AHEW for dosage and amine value as a lot fingerprint. 3.2 Comparison with Alternative Amine Hardeners Five grades cover the band, all tested against the same EEW 190 resin, so Table 3 reads across. Table 3. Published properties of five ambient-cure amine hardeners, tested against a liquid bisphenol A resin of EEW 190. Grade Chemistry Viscosity, cps AHEW, g/eq phr at EEW 190 Gel time Thin-film set Shore D 70 Bending YLH-6005 Polyetheramine, NP-free 250–450 95 50 phr 23 min 2.5 h 10 h 82.3 MPa YLH-6004 Polyetheramine, NP-free 100–300 96 50 phr 50 min 3.8 h 15 h 96.3 MPa YLH-9101 Cycloaliphatic, low VOC 250–450 92 48 phr 30 min 2.8 h 8 h Not published YLH-3023 Cycloaliphatic 250–500 100 52 phr 30 min 2.3 h 7 h 78 MPa YLH-3002 Cycloaliphatic 5000–12000 182 96 phr 30 min 1.5 h 6 h 84.1 MPa Read it by constraint, not rank. YLH-6005 leads on gel time and trails on colour at Gardner max. 3 against max. 1 for YLH-3023. YLH-6004 is slowest but strongest at 96.3 MPa. YLH-3002 sits at 5000–12000 cps and needs 96 phr, nearly twice the mass per kilo of resin. That is a design for working life in thick sections. 3.3 Decision Matrix by Application Constraint Four questions settle most enquiries. Table 4. Selection matrix for ambient-cure amine hardeners, ordered by constraint. Constraint Threshold Grade that fits What you give up Fast return to service Set under 3 h YLH-6005, 2.5 h Colour, flexural strength Light-stable topcoat Gardner 2 or less YLH-3023, max. 1 NP-free declaration Highest flexural strength Above 90 MPa YLH-6004, 96.3 MPa 3.8 h set, thin viscosity Thick-section casting High phr, low amine density YLH-3002, 96 phr Mix near 10600 mPa·s Nonylphenol-free audit Written declaration YLH-6005 or YLH-6004 Speed or colour Speed comes first: a missed recoat window costs a shift, while one Gardner point vanishes under a pigmented topcoat. If the coating is clear or light-tinted, the order reverses. 4. Formulation and Dosage Calculation Dosage for a low viscosity epoxy hardener is one line of arithmetic: phr = 100 × AHEW ÷ EEW. At AHEW 95 that reduces to 9500 ÷ EEW, so the fraction falls as resin EEW rises. Table 5. Hardener requirement for four resin EEW values at AHEW 95, with the split for a 20 kg kit. Resin EEW, g/eq Hardener, phr Resin:hardener Resin in 20 kg Hardener in 20 kg 190 50.0 phr 2.00:1 13.33 kg 6.67 kg 184 51.6 phr 1.94:1 13.19 kg 6.81 kg 170 55.9 phr 1.79:1 12.83 kg 7.17 kg 205 46.3 phr 2.16:1 13.67 kg 6.33 kg Weigh to within 1% of the hardener figure. A 2% error shifts cure speed and hardness without ruining a floor. A 10% error leaves a tacky film that never hardens, however long you wait. Blend arithmetic follows the same rule: 70 parts of EEW 190 resin with 30 parts of a 250 g/eq resin gives 205 g/eq, the last row above. 5. Processing Notes and Operating Window • Weigh, do not volume-measure. At 1.02 g/cm3 against roughly 1.16 for the resin, using the 2:1 weight ratio by volume under-doses hardener by 12%. • Mix 2 to 3 min at low shear. Air whipped in shows as pinholes in a self-levelling film and cannot be walked out. • Treat 23 min as an upper bound: it was measured on 100 g, and a 1 kg batch holds its heat and gels sooner. • Recoat between the 2.5 h set and the 10 h Shore D 70 point. If the film is past full cure, abrade before the next coat. • Below 15 °C the reaction slows and the film may stay tacky overnight. Above 30 °C pot life roughly halves. Figure 2. Applying a self-levelling epoxy floor coating; a 2.5 h thin-film set keeps the recoat window inside the same shift. The mix thins sharply: 50 phr of a 350 cps hardener takes a 13000 mPa·s resin to about 3900 mPa·s on a logarithmic mixing rule. That is what makes a solvent-free self-levelling grade practical. 6. Applications Two applications are published: epoxy flooring and electronic potting. They pull in opposite directions on cure speed. Table 6. Published applications of YLH-6005, with the property that governs each one. Application Role of the hardener Governing property Watch point Self-levelling floor Curing agent at 50 phr 23 min gel, 250–450 cps Recoat window Mortar and screed Binder with graded filler 2.5 h thin-film set Filler lifts mix viscosity Clear or tinted topcoat Curing agent at 50 phr Gardner max. 3 Colour against max. 1 grades Electronic potting Curing agent, filled system 10 h to Shore D 70 Exotherm above 1 kg pours Flooring is the intended use; the blush-free claim is scoped to a topcoat on flooring, not every climate. Figure 3. Potting a small electronic housing; gel time and exotherm, not hardness, set the size limit for a poured mass. Potting is where fast gel bites. A 23 min gel on 100 g scales badly: a 2 kg pour in an insulating housing can exotherm enough to crack around inserts. Above that mass, YLH-6004 at 50 min is safer. 7. Limitations and Material Verification 7.1 Known Limits and Where YLH-6005 Is the Wrong Choice Three published numbers argue against YLH-6005 in specific jobs. Gardner max. 3 rules out water-clear topcoats, 82.3 MPa bending is the lowest of the three grades publishing mechanical data, and a 23 min gel limits poured mass. Two gaps matter more. No CAS number is published, so customs and any REACH screening need the COA. Amine value and AHEW also fail to reconcile, so verify both on the first drum. It is also wrong where a specification asks for over 45 min of pot life at 25 °C solvent-free. Nothing published supports that. 7.2 Incoming Inspection, Packaging, Storage and Safety A first-drum check covers Gardner colour by ASTM D1544, viscosity at 25 °C, amine value by ISO 9702 and water content by ASTM E203. Add a 100 g gel time if the line is rate-sensitive. Packaging is a drum, net weight not published, and shelf life at least 12 months in unopened packing at ambient. Keep the cap closed: a modified amine picks up moisture and carbon dioxide, and the film degrades before the titration shows it. Storage needs ventilation, no flame and no direct sunlight. The hardener is alkaline and irritant, so gloves and eye protection are the minimum and the MSDS governs handling and disposal. RoHS or REACH statements belong on the COA, not here. 8. Frequently Asked Questions What mix ratio does YLH-6005 need with a standard liquid epoxy resin? At AHEW 95 g/eq it is 50 phr on an EEW 190 resin, or 2.00:1 by weight. An EEW 184 resin needs 51.6 phr, an EEW 170 resin 55.9 phr. Is YLH-6005 interchangeable with YLH-6004? No. Both take 50 phr, yet gel times are 23 min and 50 min. Swapping changes the recoat schedule, and YLH-6004 gives more flexural strength at 96.3 MPa. Does YLH-6005 eliminate amine blush? The supplier states no blushing on top of epoxy flooring coatings. Blush is a reaction between amine, moisture and carbon dioxide, so cold damp weather can still produce it. Can YLH-6005 be used for electronic potting? Electronic potting is a published application, with Shore D 70 in 10 h on a 15 g film. Above a 1 kg pour, use a slower grade. What is the CAS number of YLH-6005? None is published. Request it on the COA or TDS before the first shipment; customs and safety documents usually need it. Does YLH-6005 contain nonylphenol? It is declared nonylphenol-free on the product page. That is a formulation statement, not a certification, so get it in writing on the TDS if a customer audits. 9. Conclusions Among five ambient-cure amine hardeners, YLH-6005 is the fast option: 23 min gel and 2.5 h thin-film set against 30 to 50 min. Stoichiometry is plain: 50 phr at EEW 190, 55.9 phr on a 170 g/eq resin. The cost is Gardner max. 3 and 82.3 MPa flexure. Where speed governs, trial YLH-6005. Where colour or flexure governs, YLH-3023 at 30 min and YLH-6004 at 96.3 MPa answer better. 10. References Yolatech product page for YLH-6005: https://www.yolatech.com/curing-agnet-ylh-6005 (accessed 2026-11-04). Datasheet page for YLH-6004 at https://www.yolatech.com/curing-agnet-ylh-6004 (accessed 2026-11-04). Datasheet page for YLH-3002 at https://www.yolatech.com/curing-agnet-ylh-3002 (accessed 2026-11-04). Yolatech TDS, MSDS and COA for YLH-6005, carrying the lot CAS number; available on request. ASTM D1544, Gardner colour of transparent liquids, the method behind the colour maximum. ISO 9702, amine group nitrogen content of amine epoxide hardeners. ASTM E203, water content by Karl Fischer titration. ASTM D1652, epoxy content of epoxy resins (EEW).

1,6-Hexanediol diglycidyl ether YLD-6008 is a bifunctional water-compatible epoxy reactive diluent with EEW 142–155 g/eq. The published specification adds 10–25 mPa·s at 25 °C, APHA Max. 40 and chloride ceilings. Solvent-free coatings, laminating, adhesives and fiber finishing are the declared uses. Figure 1. Blend EEW (left) and DETA demand in phr (right) for YLE-170 with 0–30 phr of YLD-6008. Calculated from mid-band values per Section 4. 1. Introduction Aliphatic diglycidyl ethers sit between mono-epoxy diluents and base resins. Mono-epoxy grades cut viscosity hard but leave a pendant alkyl chain in the network; base resins build the network but arrive at 11,000–15,000 mPa·s. 1,6-Hexanediol diglycidyl ether YLD-6008 (CAS 16096-31-4) takes the middle route: two terminal epoxide rings on a flexible C6 spacer. This report assembles the published specification of YLD-6008, derives the formulation arithmetic, and marks the boundary of the data. Sources: the public product page (accessed 2026-10-30), values calculated from the molecular formula, and mixing-rule estimates labelled as such. 2. Materials and Methods: Identity and Published Specification of 1,6-Hexanediol Diglycidyl Ether 2.1 Product identity and specification Table 1 fixes the identity of the grade per the product page and its CAS 16096-31-4 entry. Molecular formula and weight are calculated from the structure of 1,6-bis(2,3-epoxypropoxy)hexane; dividing 230.30 g/mol by two epoxy groups gives a theoretical EEW of 115.15 g/eq. ItemInformation Trade nameYLD-6008 Chemical name1,6-Hexanediol diglycidyl ether CAS No.16096-31-4 Molecular formulaC12H22O4 (calculated) Molecular weight230.30 g/mol (calculated) Theoretical EEW115.15 g/eq (calculated, pure monomer) Table 1. Product identification of YLD-6008; calculated rows are marked as such. Table 2 lists the seven parameters the product page publishes. The measured EEW band of 142–155 g/eq lies well above the theoretical 115.15 g/eq, so the commercial liquid carries oligomeric species. That is normal for glycidyl ether diluents, and it is why the band, not the monomer value, drives formulation arithmetic. ItemSpecification AppearanceTransparent liquid Color, APHAMax. 40 Viscosity, mPa·s at 25 °C10–25 EEW, g/eq142–155 Hydrolyzable chloride, %Max. 0.2 Inorganic chlorine, ppmMax. 20 Water, %Max. 0.1 Table 2. Published specification of YLD-6008, quoted from the product page accessed 2026-10-30. 2.2 Test methods and data sources Published values are quoted as the product page states them; calculated values — molecular weight, theoretical EEW, all blend arithmetic — follow from the formulas shown; mixing-rule estimates are indicative only. For incoming control, epoxy content should be determined by titration per ASTM D1652 or ISO 3001 on each lot, water by ASTM E203 (Karl Fischer), and viscosity checked at 25 °C per ASTM D445. Buyers confirm these in duplicate on large lots. Anything beyond Table 2 should be requested as a certificate value, not assumed. 3. Results and Discussion: Structure and Reactivity of YLD-6008 3.1 What the C6 backbone does Both ends of YLD-6008 are terminal epoxies, so the molecule is built into the network on each side of the hexamethylene spacer. A mono-epoxy diluent reacts once and leaves a butyl or octyl chain dangling from the crosslink; YLD-6008 instead contributes a flexible segment between two network nodes. Flexibility comes from the spacer, participation from both rings. Two ether oxygens and short glycidyl arms sit behind the water-compatibility claim: the product page calls the grade a water-soluble reactive diluent with good wetting ability. The claim is qualitative. In practice, check the water budget of your own system first, because the specification allows up to 0.1% water in the drum and moisture pick-up after opening is a known failure path for glycidyl ethers. Viscosity is the other half of the story. 3.2 Comparison with mono-epoxy reactive diluents Table 3 lines YLD-6008 up against two mono-epoxy diluents whose specifications the site publishes in the same format. The trade-off shows in three rows: functionality, viscosity, EEW. AttributeYLD-6008YLD-9004A (BGE)YLD-7004 (C8–10) Epoxy functionality211 EEW, g/eq142–155147–157220–250 Viscosity, mPa·s at 25 °C10–25Max. 23–10 Hydrolyzable chlorideMax. 0.2%Max. 0.1%Max. 0.2% Inorganic chlorineMax. 20 ppmMax. 50 mg/kgMax. 20 mg/kg Published water-compatibility statementYes, water-soluble reactive diluentNot statedNot stated Table 3. Published parameters of YLD-6008 against two mono-epoxy reactive diluents; all values from the respective product pages. Butyl glycidyl ether YLD-9004A is the harder viscosity cutter, at a published ceiling of 2 mPa·s and a tighter hydrolyzable chloride ceiling of 0.1%. What it cannot do is react twice. When the diluent must stay in the network — flexibility, wet strength, less extractable material — the bifunctional grade earns its place. YLD-7004 wins on non-polar wetting and filler dispersion up to 15 phr; YLD-2003 publishes 25–45 mPa·s at the same APHA ceiling. Figure 2. Published viscosity bands at 25 °C (log scale) for YLD-6008, three sibling diluents and two base resins. YLD-9004A is plotted as 0.2–2 against its ceiling of 2. 4. Formulation and Dosage Calculation Blend arithmetic starts from epoxy equivalents, not from weight fractions. For a resin at EEW_r diluted with w phr of a diluent at EEW_d: EEW_blend = (100 + w) / (100/EEW_r + w/EEW_d) Table 4 works the case of YLE-170 (published EEW 160–180 g/eq) diluted with YLD-6008 at the band midpoint of 148.5 g/eq and cured with high-purity diethylenetriamine at a theoretical AHEW of 20.6 g/eq. Hardener demand barely moves: 12.1 to 12.5 phr across the whole 0–30 phr window. YLD-6008 loading, phr0102030 Blend EEW, g/eq170.0167.8166.0164.5 DETA demand, phr12.112.312.412.5 Table 4. Blend EEW and DETA demand for YLE-170 with 0–30 phr of YLD-6008; calculated from mid-band values. That flatness is the quiet advantage of a high-EEW bifunctional diluent: it thins the system without forcing a hardener rebalance. The prize is viscosity, not EEW. How far does viscosity fall? A logarithmic mixing rule on mid-band values gives the estimates in Figure 3: 15 phr of YLD-6008 takes a 13,000 mPa·s bisphenol A resin — the midpoint of the published YLE-128 band (bisphenol A epoxy resin, 11,000–15,000 mPa·s) — to roughly 5,500 mPa·s, against about 4,000 for BGE. Treat both as directional and measure the real blend at 25 °C before it reaches a work instruction. Figure 3. Estimated blend viscosity at 15 phr loading in YLE-128, logarithmic mixing rule on mid-band published values. Indicative only. Chloride arithmetic matters when the end use is electrical. At the 0.2% hydrolyzable chloride ceiling, 15 phr of YLD-6008 adds about 261 ppm on a (100 + 15) mass basis; 30 phr adds about 462 ppm. Run it alongside the 20 ppm inorganic chlorine ceiling before any electronics trial. 5. Processing Notes and Operating Window Add YLD-6008 to the resin side and homogenize before the hardener joins; the order matters less for epoxy equivalents than for wetting. Start at 10–20 phr for coatings and laminating; push toward 25–30 phr only where flexibility leads. A starting point, not a specification. Close the drum tightly after each use; keep stock away from flames and sunlight. Below 15 °C the 10–25 mPa·s band drifts upward; check viscosity at the real shop temperature. When a chloride ceiling applies, run the ppm arithmetic of Section 4 before the trial. One rule of thumb covers most shops: pick the loading from the viscosity the process tolerates, then confirm cure behaviour and mechanical properties sit where they did before. Pot life depends on hardener, filler and batch temperature; a jar test at n = 3 replicates is worth the hour. 6. Applications: Where YLD-6008 Is Published to Work Four use classes appear on the product page; Table 5 pairs each with its pre-scale-up check. ApplicationPublished role of YLD-6008Check before scale-up Solvent-free coatingsToughening diluent; cuts viscosity and lets filler loading riseFilm hardness and pot life at plant temperature Laminating and impregnationBetter wet-out and penetration during castingBath viscosity drift over a working shift AdhesivesFlexibility at the bond lineLap shear after water soak Fiber finishingFlexibility, fastness, alkali resistance and dyeability of fiberFastness on the actual fabric Table 5. Published applications of YLD-6008 and the verification each one needs. The fiber finishing row is the least generic of the four. It matches the water-compatibility claim, and it is where the C6 spacer competes with textile chemistry rather than with other epoxy diluents. 7. Limitations and Material Verification 7.1 Known limitations and unsuitable uses YLD-6008 is not a low-chlorine grade. Its 0.2% hydrolyzable chloride ceiling is looser than the 0.1% of BGE and much looser than the 500 ppm total-chlorine specification published for 1,4-butanediol diglycidyl ether YLD-6018L. For electronic encapsulation with tight ionic limits, that difference decides the selection. Density, flash point, refractive index, gel time and Tg effects are not published for this grade. Do not import them from sibling grades; the glycol spacer shifts all of them. The EEW band also deserves respect: a formulation balanced on the theoretical 115.15 g/eq instead of the 142–155 g/eq band will over-cure. The band is the spec. 7.2 Incoming verification, packaging and storage Verify each lot against Table 2: epoxy content determined by ASTM D1652 or ISO 3001 titration, water by ASTM E203, viscosity measured at 25 °C, color on the APHA scale. A duplicate determination per lot costs little compared with a salvaged batch. Packaging is a drum; shelf life is at least 12 months from manufacture in the original unopened packing at ambient temperature. Storage wording is published: a well-ventilated area, away from flames and direct sunlight, cap closed after each use. Handling detail beyond the page belongs to the MSDS. 8. Frequently Asked Questions What is YLD-6008 used for in an epoxy formulation? Cut the viscosity of the base resin, stay in the network as a bifunctional co-reactant, and add flexibility through the C6 spacer. Published uses cover solvent-free coatings, laminating, adhesives and fiber finishing. How much 1,6-hexanediol diglycidyl ether should be added? Start at 10–20 phr for coatings, laminating and adhesives; move toward 25–30 phr only when flexibility or wetting demands it. The right value depends on base resin viscosity and the process window; treat every starting number as a first trial point confirmed by measurement. Is YLD-6008 water soluble? The product page describes the grade as a water-soluble reactive diluent with good wetting ability. No solubility value is published; read the claim as qualitative. If an aqueous phase is central to your process, request solubility data first. How does YLD-6008 differ from butyl glycidyl ether? Functionality first: YLD-6008 carries two epoxide groups against one for BGE. The published EEW bands are close (142–155 versus 147–157 g/eq), while BGE is the stronger viscosity cutter at a ceiling of 2 mPa·s and a tighter hydrolyzable chloride ceiling of 0.1% versus 0.2%. Trade-off, not superiority. Does YLD-6008 change the amine hardener dosage? Barely. On a bisphenol F resin at EEW 170, calculated DETA demand rises from 12.1 to 12.5 phr across a 0–30 phr window, because the diluent EEW sits near the resin EEW. Do not expect a hardener cut here. What should be checked when a YLD-6008 drum arrives? Epoxy equivalent weight by ASTM D1652 or ISO 3001 titration, water by ASTM E203, viscosity at 25 °C and APHA color, against Table 2. Confirm the drum seal, the 12-month shelf-life window and the storage conditions on the label. 9. Conclusions YLD-6008 is a bifunctional reactive diluent whose published numbers are internally consistent: EEW 142–155 g/eq, viscosity 10–25 mPa·s at 25 °C, and chloride and water ceilings verifiable by standard titration. Blend arithmetic shows it thins a bisphenol F resin without moving amine demand, which keeps reformulation low-risk on the cure side. The limits are equally clear: a 0.2% hydrolyzable chloride ceiling that rules out tight ionic budgets, and unpublished constants that must come from the TDS or COA. 10. References [1] Yolatech product page, 1,6-Hexanediol diglycidyl ether YLD-6008: https://www.yolatech.com/16-hexanediol-diglycidyl-ether-yld-6008 (accessed 2026-10-30). [2] Yolatech Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis for YLD-6008, CAS 16096-31-4 (available on request). [3] ASTM D1652, epoxy content of epoxy resins (EEW). [4] ISO 3001, determination of epoxy equivalent. [5] ASTM E203, water content by Karl Fischer titration. [6] ASTM D445, kinematic viscosity.

Styrenated phenol MSP-250 is a colorless to pale yellow phenolic liquid with a hydroxyl value of 230-260 mg KOH/g and a viscosity of 300-800 mPa.s at 25 C. It is used at 1.0-3.0 phr to replace restricted nonylphenol in amine and anhydride epoxy systems. Grade data, dosage maths and limits are shown. Figure 1. MSP-250 as supplied: a low-viscosity phenolic liquid that pours at room temperature. 1. Introduction: Why Nonylphenol Substitution Is a Formulation Problem Nonylphenol has done three jobs in amine-cured epoxy for decades: it cuts viscosity, it accelerates the cure, and it dissolves in almost anything. A replacement has to keep the cure profile and the flow behaviour, not just the label. Styrenated phenol comes from the same family: acid-catalysed alkylation of phenol with styrene gives a mono- to hepta-styrenated mixture, and one phenolic hydroxyl survives. MSP-250 is the Yolatech grade, and its published hydroxyl value of 230-260 mg KOH/g sits close to nonylphenol on an equivalent basis. This report separates measured from calculated values, then works through the regulatory position and the dosing arithmetic. Numbers stop where the MSP-250 product page stops. 2. Materials and Methods: Styrenated Phenol MSP-250 Grade Data 2.1 Product Identification and Published Specification Table 1 puts identity and specification on one screen. Values marked calculated are arithmetic from the published hydroxyl value. Table 1. Identity and published specification of styrenated phenol MSP-250. Item Value and basis Chemical identity Styrenated phenol, mono- to hepta-styrenated mixture, one phenolic hydroxyl per molecule CAS No. 61788-44-1 (phenol, styrenated) per the site keyword block; the page intro prints 462-94-2, which is 1,5-diaminopentane. Confirm on the SDS and COA. Appearance Colorless to light yellow liquid Hydroxyl value 230-260 mg KOH/g (published) Hydroxyl equivalent 216-244 g/eq, calculated as 56100 / hydroxyl value Viscosity 300-800 mPa.s at 25 C (published) Water 0.50 % maximum (published) Purity line Printed as 2 % maximum, basis not stated; treat as unconfirmed until the TDS defines it Solubility Soluble in ethanol, acetone, benzene, toluene, trichloroethane; insoluble in water Dosage and packing 1.0-3.0 parts per 100 parts resin; 25 kg, 200 kg and 1000 kg drums; 12 months shelf life 2.2 Test Methods and Data Sources Nothing in Table 1 was measured for this report. Table 2 gives the basis of each value and the method on re-test. Table 2. Basis of each published value and the method to request on re-test. Property Status Method to quote Hydroxyl value Published window Method stated in the current TDS; not named on the page Viscosity Published at 25 C Rotational spindle, measured at 25 C; ASTM D445 is kinematic and not interchangeable Water Published maximum ASTM E203, Karl Fischer titration Flash point Not published ASTM D93, Pensky-Martens closed cup; ask for the figure 3. Results and Discussion 3.1 How One Phenolic Hydroxyl Becomes a Chain End The phenolic hydroxyl opens an epoxide ring and stays bonded to the network as a beta-hydroxy ether. That much is covalent. It is not a crosslink. Each molecule carries one hydroxyl, so reaction with a diepoxide caps a chain end instead of joining two chains, and crosslink density falls with dose. The page calls this covalent crosslinking; a monofunctional phenol cannot deliver that. Three other effects explain the reported benefits. The phenol hydrogen-bonds the amine hardener and speeds epoxide opening, so gel time shortens and peak exotherm can rise. The styryl group lowers blend viscosity without volatile solvent. The aromatic ring absorbs UV, the usual explanation for color retention at 60 C. 3.2 Styrenated Phenol, Nonylphenol and Benzyl Alcohol Compared Table 3 sets styrenated phenol against the two liquids it most often replaces. Equivalent weights are calculated, so the dose column compares like with like. Table 3. Styrenated phenol MSP-250 against nonylphenol and benzyl alcohol. Property MSP-250 Nonylphenol Benzyl alcohol Hydroxyl equivalent 216-244 g/eq about 255 g/eq, calculated about 108 g/eq, calculated Network effect Chain cap, slight plasticizing Chain cap, slight plasticizing Non-reactive plasticizing Color at 60 C Reported better after 3 days Reference Good, volatile loss REACH entry 46 Not listed Listed, 0.1 % w/w limit Not listed Typical dose 1.0-3.0 phr 1.1-3.3 phr at equal hydroxyl 2-6 phr The regulatory column gets misread. Annex XVII entry 46 covers nonylphenol and its ethoxylates at 0.1 % w/w or above in named uses: industrial and domestic cleaning, textile and leather processing, metal working, pulp and paper, cosmetics, and co-formulants in pesticides. Coatings and adhesives are not on that list, so the pressure on a paint formulator arrives through a customer declaration or a brand restricted substance list. The grade is not restricted under that entry. That is a fact about the entry, not a safety verdict. Where a bio-based phenol is preferred, cardanol glycidyl ethers cover a different part of the decision. 4. Formulation and Dosage Calculation: from phr to Epoxide Consumption Three lines of arithmetic cover most substitution cases, but the right dose depends on the hardener and the filler load. EEW(OH) = 56100 / hydroxyl value, so 230-260 mg KOH/g gives 216-244 g/eq. At 3 phr, n(OH) = 3 / 230 = 0.013 eq. A bisphenol A epoxy resin at EEW 185 g/eq holds 0.541 eq of epoxide per 100 g, so the phenol consumes 2.4 % of it. Table 4. Epoxide consumption at published dose levels, resin EEW 185 g/eq. MSP-250 dose Hydroxyl added Epoxide present Consumed 1.0 phr 0.0043 eq 0.541 eq 0.8 % 3.0 phr 0.0130 eq 0.541 eq 2.4 % 5.0 phr 0.0217 eq 0.541 eq 4.0 % 3.3 phr nonylphenol 0.0129 eq 0.541 eq 2.4 % A 3.3 phr nonylphenol dose supplies 0.0129 eq; the same figure from MSP-250 needs 3.0 phr, because its equivalent weight is lower. Swapping by mass leaves the phenol side under-dosed, and the slower cure then gets blamed on the new raw material. Dosage is not fixed. With a YLH-102G4 modified amine hardener the 1.0-3.0 phr window is a reasonable start. With an anhydride such as MHHPA, the phenol competes with the anhydride for epoxide and also accelerates, so set the dose on trial coupons. Check with the hardener supplier before assuming additivity. 5. Processing Notes and Operating Window MSP-250 goes into the hardener component in most two-pack systems, and into the resin side only when the hardener is a solid. Three points cover the usual failures: - Pre-blend at 30-40 C with low-shear agitation. If the blend exceeds 60 C, the color starts to drift. - Seal the drum within minutes. An open drum in a humid plant picks up water and clouds a clear system. - Re-check gel time after the swap. Two minutes shorter at 25 C is normal; ten minutes means the dose is too high. Figure 2. Adding MSP-250 to the hardener at 30-40 C keeps color inside the light yellow band. 6. Applications The published list runs from heavy-duty anticorrosion to electronic potting. Table 5 maps each use to its function and to the point where a formulator should slow down. Table 5. Applications of styrenated phenol MSP-250 and their operating notes. Application Function Start dose Where it goes wrong Marine and maintenance coatings Viscosity cut, faster cure 1.5 phr Pot life drops in a 20 kg kit Primers and sealants Wetting and adhesion 2.0 phr Soft primer that will not sand Adhesives and potting Flow control at low filler 1.0 phr Water pickup clouds a casting Curing agent blends Nonylphenol replacement Equal hydroxyl Matching by mass under-doses Heavy-duty anticorrosion is the largest outlet, and it is where the YLH-9101 amine hardener pairing shows up most often. If clarity matters, 3 phr is the practical ceiling in a white topcoat. Figure 3. Heavy-duty marine coatings are the main outlet for phenolic modifiers at 1-3 phr. 7. Limitations and Material Verification 7.1 Known Limits and Where MSP-250 Is the Wrong Choice Three applications should stay with another material. Laminates needing a glass transition above 120 C cannot absorb a chain cap, systems where nonylphenol was an emulsifier need a surfactant, and white topcoats typically fail above 3 phr. Data gaps matter as much. No flash point, density, molecular weight or free phenol figure is published, yet each appears in a transport document or customer questionnaire. The page also prints CAS 462-94-2, which belongs to 1,5-diaminopentane, while the keyword block prints 61788-44-1 for phenol, styrenated. Until the SDS and COA agree, neither number belongs in a customs declaration. 7.2 Incoming Inspection, Packaging, Storage and Safety A phenolic raw material is easy to accept on appearance but hard to defend later. Table 6 is the minimum a receiving lab should record per batch. Table 6. Incoming inspection record for styrenated phenol MSP-250. Check How Accept Appearance Visual, 200 mL sample in a clear jar Colorless to light yellow, no haze or sediment Hydroxyl value Duplicate titration, n = 2 230-260 mg KOH/g Viscosity Rotational spindle, measured at 25 C 300-800 mPa.s Water ASTM E203, Karl Fischer 0.50 % maximum Free phenol Gas chromatography, supplier method Limit agreed with the supplier; the page prints 2 % without a basis Documents SDS, COA, batch number, manufacture date CAS identical on all three; 12 months shelf life on arrival Store ventilated, away from flame and sunlight, cap closed after use; drums come at 25 kg, 200 kg and 1000 kg. Keep the material above 15 C in winter, because a cold drum thickens and partial mixing gives a viscosity that will not repeat. All handling information is provided in the Material Safety Data Sheet, and the batch Certificate of Analysis governs the shipment. 8. Frequently Asked Questions Is styrenated phenol MSP-250 a drop-in replacement for nonylphenol? It is close, not identical. MSP-250 matches nonylphenol on phenolic hydroxyl and viscosity class, so the dose transfers after an equivalent-weight correction. Cure speed and color drift still need a trial unless the hardener is unchanged. What dose of styrenated phenol replaces 3 phr of nonylphenol? About 2.7 phr on hydroxyl equivalents. Nonylphenol at 3 phr supplies 0.0118 eq; MSP-250 at 230 g/eq supplies the same at 2.7 phr. Round up to 3.0 phr if the system needs extra flow. Does MSP-250 react into the epoxy network or only plasticize it? It reacts, but each molecule offers one hydroxyl, so it terminates a chain rather than joining two. The bond is covalent and the effect is still plasticizing, because crosslink density drops as dose rises. Why does the product page show two different CAS numbers? The introduction prints 462-94-2 and the keyword block prints 61788-44-1. The second is phenol, styrenated; the first is 1,5-diaminopentane. Confirm the number on the SDS before filing. Can MSP-250 be used in solvent-free or high-solids systems? Yes, and that is where it earns its place. At 1.0-2.0 phr it lowers mix viscosity in a 100 % solids coating without adding VOC. How should MSP-250 be stored and re-tested? Keep drums closed, ventilated, away from flame and sunlight, between 15 C and 30 C. Shelf life is at least 12 months; re-test hydroxyl value and water on older stock. 9. Conclusions MSP-250 is a workable nonylphenol substitute in amine and anhydride epoxy systems, provided the swap is done on hydroxyl equivalents rather than on mass. A 3 phr dose consumes about 2.4 % of the epoxide groups in an EEW 185 resin: small enough to keep mechanical properties, large enough to change flow and gel time. The regulatory argument needs care. Nonylphenol is restricted under REACH Annex XVII entry 46 for a list of uses that does not include coatings, so the pressure is commercial and documentary. Styrenated phenol avoids that entry. Two items should be closed before a shipment is booked: the CAS number on the SDS, and the basis of the purity line. 10. References 1. Yolatech product page, styrenated phenol MSP-250: https://www.yolatech.com/styrenated-phenol-msp-250 (accessed 2026-10-27). 2. Yolatech Technical Data Sheet for MSP-250, available on request. 3. Yolatech Material Safety Data Sheet and Certificate of Analysis for MSP-250, available per batch. 4. ASTM D1544, Gardner color of transparent liquids. 5. ASTM E203, water content by Karl Fischer titration. 6. ASTM D93, flash point, Pensky-Martens closed cup. 7. Regulation (EC) No 1907/2006, Annex XVII, entry 46, consolidated text: https://eur-lex.europa.eu (accessed 2026-10-27).

Tetrafunctional epoxy resin YLSE-721 is a four-epoxy-group aniline epoxy sold in three versions with EEW 105-125 g/eq. Chemically it is 4,4'-methylenebis(N,N-diglycidylaniline); its rigid core pushes crosslink density and heat resistance past bisphenol A resins. Grade data, dosage and limits follow. Figure 1. YLSE-721 ships as a yellow viscous liquid; the three grades share one appearance specification. 1. Introduction Filament winding and high-temperature adhesive work both punish difunctional resins. Bisphenol A diglycidyl ether networks soften well before 150 °C, so formulators needing mechanical properties near 200 °C move to multifunctional aniline epoxies. Tetrafunctional epoxy resin YLSE-721 is the Yolatech grade for that job: the product page names filament-wound composites, long pot life at process temperature and high Tg. This report compiles what the YLSE-721 product page publishes, separates it from calculated values, and works through grade selection, dosage and field limits. Numbers stop where the page stops. Nothing here replaces the current TDS. 2. Materials and Methods: Tetrafunctional Epoxy Resin YLSE-721 Grade Data 2.1 Product Identification and Specification Table 1 collects identity data. Molecular weight and the theoretical equivalent are calculated from the chemical name; the CAS number comes from third-party databases because the page does not list it. Table 1. Identity of 4,4'-methylenebis(N,N-diglycidylaniline) YLSE-721. Item Information Chemical name 4,4'-methylenebis(N,N-diglycidylaniline) CAS No. Not published on the product page; 28768-32-3 per third-party databases, confirm on the COA Molecular formula / MW C25H30N2O4 / 422.52 g/mol, calculated from the chemical name Functionality 4 epoxy groups (stated on the page: tetrafunctional) Theoretical EEW 105.6 g/eq, calculated (422.52 / 4); published window 105-120 g/eq for YLSE-721 Table 2 reproduces the published grade table; the versions share one chemistry and differ in viscosity, price and purity positioning. Table 2. Published specification of the three YLSE-721 grades. Item YLSE-721L YLSE-721C YLSE-721 Appearance Yellow liquid Yellow liquid Yellow liquid Color, Gardner 10 or below 10 or below 10 or below Viscosity, cps (see 7.1) 6000-11000 (25 °C) 3000-7000 3000-7000 EEW, g/eq 110-125 110-125 105-120 Volatiles, % 0.6 or below 0.6 or below 0.6 or below Positioning Lower viscosity Lower price High purity 2.2 Test Methods and Data Sources Three data classes are kept apart. Published values come from the product page. Calculated values, such as the 105.6 g/eq theoretical equivalent, follow from arithmetic on published facts. Third-party values, such as CAS 28768-32-3, carry their own attribution and are not treated as supplier data. In release testing the epoxy equivalent is normally determined by titration according to ASTM D1652 or ISO 3001, and Gardner color is measured according to ASTM D1544; the page does not state its internal methods, so the inspection plan in 7.2 fixes them instead. 3. Results and Discussion 3.1 Structure and Reactivity: Four Epoxy Groups on a Rigid Aniline Core Four epoxy groups per 422.52 g/mol molecule set the ceiling on crosslink density. A fully reacted YLSE-721 network carries roughly twice the junction density of a difunctional resin of similar equivalent weight, the structural reason behind the high Tg and hot mechanical retention. Two secondary effects matter in practice. Tertiary aniline nitrogens left after glycidylation catalyze their own cure, which supports the long pot life the page describes; the same activity means accelerator dosing must be trimmed, not added blindly. The aromatic backbone resists chain scission, backing the radiation and chemical resistance claims. Pot life is not a free gift: when the winding bath sits warm for hours, viscosity still drifts, and bath turnover discipline decides the day's consistency. 3.2 Comparison with Alternative Systems Table 3 sets YLSE-721 against the two closest alternatives in the portfolio: trifunctional aminophenol YLSE-0500 and liquid tetrafunctional YLD-1240. All values are published, viscosity at 25 °C where stated. Table 3. Property comparison of YLSE-721 with alternative multifunctional systems. Attribute YLSE-721 (this product) YLSE-0510 (alternative) YLD-1240 (alternative) Functionality 4 (tetrafunctional) 3 (trifunctional) 4 (tetrafunctional) EEW, g/eq 105-120 93-106 95-110 Viscosity, cps at 25 °C 3000-7000 (721/721C) 400-900 1600-3000 Trade-off Highest Tg potential, stiff processing Easiest flow, lower crosslink density Lowest viscosity among the tetrafunctional grades Best fit Filament-wound hot-service vessels Fast wet-out laminating Casting where heat resistance meets flow The hierarchy is strict. If the part must hold stiffness near 200 °C, the tetrafunctional aniline core wins, and the viscosity price is paid through heated lines or a diluent such as YLD-6008 hexanediol diglycidyl ether. If wet-out speed dominates and service temperature stays moderate, the low-viscosity trifunctional N,N-diglycidyl-4-glycidyloxyaniline YLSE-0500 series fits better. The liquid tetrafunctional grade YLD-1240 sits between them, while YLSE-0600 aniline epoxy resincovers cases needing a pendant glycidyl ether for flexibility. 4. Formulation and Dosage Calculation Dosage follows the standard equivalent relationship: phr = 100 × AHEW ÷ EEW, with AHEW the amine hydrogen equivalent weight of the curative and EEW the epoxy equivalent of the resin. Table 4 evaluates both ends of the published YLSE-721 window, 105 and 120 g/eq, with curatives documented on the Yolatech site. The anhydride row applies the 0.85 empirical factor. Table 4. Calculated curative demand for YLSE-721 at the published EEW limits. Curative AHEW, g/eq phr at EEW 105 phr at EEW 120 PACM cycloaliphatic diamine 52.6 (calculated) 50.1 43.8 MHHPA liquid anhydride, factor 0.85 168.19 (calculated) 136.1 119.1 YLH-9101 modified amine 92 87.6 76.7 YLH-3002 modified amine 182 173.3 151.7 Dosage matters. Treat every number in Table 4 as a calculated starting point, not a specification. Aerospace practice cures aniline tetrafunctional resins with aromatic amines, outside the current Yolatech portfolio; those systems typically run a staged schedule with a postcure well above 150 °C to reach the promised Tg. When a first trial is mixed, gel time and a DSC scan on the actual curative lot decide the schedule; accelerator level swings gel time by hours. The theoretical equivalent, 105.6 g/eq, sits inside the published window, a useful cross-check that the grade is close to neat monomer. 5. Processing Notes and Operating Window Handling a 3000-11000 cps aniline resin is mostly heat management and bath hygiene. - Warm the resin gently before metering; even 40-50 °C cuts batching time sharply.- Degas after adding curative; entrained air in a filament-wound wall becomes a void path.- Keep bath temperature steady during winding; pot life still degrades once the batch is catalyzed.- Dilution with a mono- or difunctional ether lowers viscosity but trades away Tg; weigh that before adding much.- Postcure above 150 °C where the part geometry allows; undercured aniline networks look done and creep in service. Figure 2. Filament winding, the first process the page names for YLSE-721; bath viscosity stability and degassing decide quality. 6. Applications: Filament Winding and Structural Adhesive The page names two application fields: carbon and glass fiber composites, and structural adhesive for 200-260 °C service. Table 5 lists each with the resin's role. Table 5. Published application fields and the role of YLSE-721 in each. Application Role of YLSE-721 Process note Carbon fiber composites Matrix resin for high-temperature parts Filament winding or prepreg route Glass fiber composites Matrix resin where cost is tighter 721C positioning favors volume Structural adhesive, 200-260 °C Heat-resistant adhesive base Joint design must share the thermal load Figure 3. In the 200-260 °C structural adhesive field, the aniline network holds the bondline; bisphenol A systems creep. 7. Limitations and Material Verification 7.1 Known Limitations and Unsuited Uses Three published facts deserve a caution flag. First, the viscosity row of the grade table carries the header "cps at 50 °C", yet the YLSE-721L cell is annotated "25 °C", and the L grade is labeled "Lower viscosity" while showing 6000-11000 against 3000-7000 for the other two. Those numbers cannot share one basis, so confirm the temperature in the current TDS before comparing quotes. Second, the page publishes no CAS, density, flash point or Tg; CAS 28768-32-3 comes from third-party databases and should be verified on the COA before customs or compliance work. Third, color stops at Gardner 10 or below and the liquid is yellow, so clear or decorative parts are not a fit. The page also lists "fast curing speed at room temperature" while describing long pot life at process temperatures. Those statements pull against each other, as they do across multifunctional aniline systems; in practice the cure schedule depends on the curative and accelerator package, not on the resin alone. If a room-temperature schedule without postcure is a hard requirement, this is not the right resin family. 7.2 Incoming Inspection, Packaging, Storage and Safety A four-line incoming check catches most lot problems: EEW by titration according to ASTM D1652 or ISO 3001, viscosity by the method stated in the TDS, color according to ASTM D1544, and volatiles on a fresh sample in duplicate. Storage follows the page: a well-ventilated area away from flames and sunlight, cap closed immediately after use, at least 12 months in the original packing at ambient temperature. Part-used drums deserve a nitrogen blanket; the epoxy groups are moisture-sensitive over long standing. All safety information is provided in the Material Safety Data Sheet, the governing document for handling and transport; check it before shipping, since the flash point is unpublished. 8. Frequently Asked Questions What is the difference between YLSE-721, 721C and 721L? One chemistry, three positionings. YLSE-721 carries the tightest EEW window at 105-120 g/eq and the high-purity label, YLSE-721C is priced for volume at EEW 110-125 g/eq, and YLSE-721L is the lower-viscosity version at 6000-11000 cps (25 °C) and EEW 110-125 g/eq. Verify the viscosity basis with the supplier first, per 7.1. Which curing agents suit tetrafunctional epoxy resin YLSE-721? Equivalent-weight arithmetic makes any polyfunctional amine or anhydride usable; Table 4 works the numbers for PACM, MHHPA, YLH-9101 and YLH-3002. For maximum service temperature, anhydride or aromatic amine systems with a staged postcure are standard; aliphatic amines cure faster but cap heat performance. Why does the viscosity table show two temperature bases? The column header reads 50 °C, but the YLSE-721L cell is annotated 25 °C. Epoxy viscosity falls steeply with temperature, so the two bases differ by a factor of several. Confirm the basis per grade; never quote a mixed comparison to a customer. Can YLSE-721 replace a bisphenol A resin such as YLE-128? No, and the substitution fails in both directions. YLE-128 flows at 11000-15000 mPa·s with EEW 184-190 g/eq and cures into a network that softens far below what YLSE-721 delivers; conversely, YLSE-721 costs more, processes stiffer, and its aniline network is wasted on ambient service parts. Choose by service temperature, not by habit. What dosage should a first MHHPA trial with YLSE-721 use? The Table 4 value is 136.1 phr at EEW 105 g/eq and 119.1 phr at EEW 120 g/eq, calculated with the 0.85 anhydride factor. Start near 120-135 phr with the usual 0.5-2 phr tertiary amine accelerator, run a gel time check, then adjust against DSC data. How should YLSE-721 be stored after a drum is opened? Follow the page: close the cap tightly after use, keep the drum in a ventilated area away from flames and sunlight, and use the contents within 12 months of manufacture. For a drum standing open for weeks, blanket it with dry nitrogen to limit moisture uptake and viscosity drift. 9. Conclusions Tetrafunctional epoxy resin YLSE-721 gives formulators a documented route to high-crosslink, heat-resistant networks. Three grades cover EEW 105-125 g/eq, the calculated theoretical equivalent of 105.6 g/eq matches that window, and the published application fields are filament-wound composites and 200-260 °C structural adhesive. The open items are equally concrete: the grade table's viscosity basis needs TDS confirmation, CAS and physical constants are unpublished, and cure schedules must be validated per curative lot. Grade choice reduces to a single question: which constraint binds first, flow, price or purity. 10. References 1. Yolatech product page: 4,4'-Methylenebis(N,N-diglycidylaniline) YLSE-721/721C/721L, https://www.yolatech.com/44-methylenebisnn-diglycidylaniline-ylse-721721c721l (accessed 2026-10-26). 2. Yolatech product page: N,N-diglycidyl-4-glycidyloxyaniline YLSE-0500/0510/0510L, https://www.yolatech.com/44-methylenebisnn-diglycidylaniline (accessed 2026-10-26). 3. Yolatech product page: YLD-1240, https://www.yolatech.com/curing-agent-ylh-102g4 (accessed 2026-10-26). 4. Yolatech Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis for YLSE-721, YLSE-721C and YLSE-721L (available on request). 5. ASTM D1652, test method for epoxy content of epoxy resins. 6. ISO 3001, determination of epoxy equivalent. 7. ASTM D1544, Gardner color of transparent liquids.

PACM epoxy curing agent is a colourless alicyclic diamine, 4,4'-diaminodicyclohexyl methane (CAS 1761-71-3), sold at 50-80 mPa·s and APHA 30 or below. Four amine hydrogens on a 210.36 g/mol molecule give a calculated AHEW of 52.6 g/eq, which puts YLE-128 at 28.1 phr. Specification and dosage follow. Figure 1. Calculated demand for PACM (52.6 g/eq), MACM (60 g/eq) and DACH (28.5 g/eq) across 120-220 g/eq; marked points are the grades in Table 4. 1. Introduction: Why the Unsubstituted Ring Matters Alicyclic diamine hardeners suit coatings that must stay hard and stay light in colour but cannot take the short pot life of diethylenetriamine. PACM is the unsubstituted member of that family: two cyclohexane rings joined by a methylene bridge, each carrying one primary amine. Its published specification is five lines and one CAS number, with viscosity at 50-80 mPa·s at 25 °C. Melting point, flash point and density are not on the page, so they are left out here rather than filled from memory. Three sources feed the numbers: the PACM product page, three comparable alicyclic diamines from the same catalogue, and stoichiometry. 2. Materials and Methods: PACM Epoxy Curing Agent Specification One CAS number and four lines pin the identity down. 2.1 Product Identification and Published Limits Table 1 lists the identifiers that belong on a purchase order and on the COA review sheet. Table 1. Product identification of PACM; values marked calculated come from molecular structure, not from the product page. Item Information Trade designation PACM Chemical name 4,4'-Diaminodicyclohexyl methane CAS No. 1761-71-3 Molecular formula (calculated) C13H26N2 Molecular weight (calculated) 210.36 g/mol Amine hydrogen equivalent weight (calculated) 52.6 g/eq from four active hydrogens Appearance Colourless or slightly yellow transparent liquid, packed in drums Table 2 repeats the five published limits beside the test basis a laboratory would normally apply to each. Table 2. Published specification of PACM with the corresponding test method. Item Published limit Test basis Appearance Colourless liquid, no suspended matter visual, per current TDS Colour APHA 30 maximum ASTM D1544 Viscosity at 25 °C 50-80 mPa·s ASTM D445 Purity 99.0% minimum supplier method Water 0.20% maximum ASTM E203 2.2 Test Methods and Data Sources Resin epoxy equivalent weight is determined by titration according to ASTM D1652, with ISO 3001 as the alternative route. Colour is read according to ASTM D1544 against the Gardner scale, viscosity according to ASTM D445 at 25 °C. Water moves first after a drum is opened, so it is measured by Karl Fischer titration according to ASTM E203 on duplicate portions, reported as the mean of n = 3. Amine hydrogen equivalent weight is not printed on the product page. It follows from molecular weight divided by active hydrogens: 210.36 ÷ 4 = 52.59 g/eq. That arithmetic reproduces two published values on the same catalogue, 60 g/eq for MACM and 28.5 g/eq for DACH, to within 1%, which is why 52.6 g/eq is used in every dosage table here. 3. Results and Discussion: Ring Geometry and Cure Response Ring geometry, not molecular weight, separates PACM from the linear aliphatic amines. 3.1 Why the Cyclohexane Ring Changes Hardness and Colour Both amines sit on a cyclohexane ring, making them primary amines on secondary carbons. Steric hindrance there slows the addition to an epoxide, so a PACM mix stays workable longer than a DETA mix of the same equivalent weight. Crosslink density moves the other way. At 52.6 g/eq with four hydrogens, PACM creates more network junctions per 100 g of resin than a 60 g/eq hardener, and the rigid ring lifts hardness and heat deflection without aromatic structure. Colour holds because no aromatic chromophore is present to yellow under UV, although the surface stays a primary amine that reacts with carbon dioxide. 3.2 Comparison with Alternative Diamine Hardeners Table 3 sets the PACM epoxy curing agent beside three alicyclic diamines from the same catalogue, on the lines that decide a formulation. Table 3. Published properties of four alicyclic diamine hardeners; calculated AHEW values follow the method in section 2.2. Property PACM MACM DACH 1,3-BAC CAS No. 1761-71-3 6864-37-5 694-83-7 2579-20-6 Ring substitution none two methyl none aminomethyl arms Colour, APHA 30 max 30 max 30 max not published Viscosity, 25 °C 50-80 mPa·s 80-120 mPa·s not published not published Water 0.20% max not published 0.3% max 0.3% max AHEW 52.6 g/eq 60 g/eq 28.5 g/eq 35.6 g/eq Dosage tracks the equivalent weight almost linearly. On a 187 g/eq bisphenol A resin, DACH needs 15.2 phr, 1,3-BAC 19.0 phr, PACM 28.1 phr and MACM 32.1 phr at the same stoichiometry. Viscosity is where the grade earns its place: 50-80 mPa·s carries more filler and less solvent than MACM at 80-120 mPa·s, which decides whether a high-solids primer stays under a VOC ceiling. Speed is the trade-off: DACH reacts fast at 28.5 g/eq and suits thin films in a cold shop, but rules itself out of a 3 mm casting. 4. Formulation and Dosage Calculation Dosage comes from one equation: phr = 100 × AHEW ÷ EEW, with 52.6 g/eq for PACM and the EEW of the resin actually in the pot. Table 4 applies it to four resins at full and 0.90 stoichiometry. Table 4. Calculated PACM demand in phr for four Yolatech resins, at 1.00 and 0.90 stoichiometric index. Resin EEW, g/eq Dosage at 1.00 index, phr Dosage at 0.90 index, phr YLCE-2021 125-135 39.0-42.1 35.1-37.9 YLE-170 160-180 29.2-32.9 26.3-29.6 YLE-127 176-184 28.6-29.9 25.7-26.9 YLE-128 184-190 27.7-28.6 24.9-25.7 A 0.90 index leaves about a tenth of the epoxide unreacted. In practice most ambient-cure coatings run there, because a slight amine excess tolerates surface moisture and carbon dioxide better than an exact ratio. Below 0.85 the film stays soft and chemical resistance drops; above 1.05 the surplus amine plasticises the network and pushes colour up. Neither end recovers with longer curing, so verify the index before scaling up. The same equivalent weight serves polyurethane work: against an isocyanate equivalent of 42.02 g/eq, 100 g of NCO groups consume 125.2 g of PACM. 5. Processing Notes and Operating Window Four settings decide whether a PACM system behaves in the plant the way it did in the laboratory. Mix by weight, never by volume. Density differences between a filled resin and an amine shift volume ratios by several percent. Keep the shop between 18 and 30 °C. Below 10 °C the addition reaction slows sharply and a 24-hour cure stretches to three days; if the plant runs colder, extend induction and accept overnight tack. Hold relative humidity under 70%. Beyond that, carbamate forms faster than the film cures and the haze is permanent. Post-cure at 80 °C for 2 hours where heat deflection matters; no Tg is published, so confirm on your own laminate. Figure 2. Temperature bands for a PACM-cured ambient system; the 18-30 °C band holds both the published viscosity and a 24-hour cure. Batch size is the practical control on exotherm. Five kilograms in a thin tray is safe at 25 °C; the same five kilograms in a 20 cm drum will gel in the pot. 6. Applications Five roles appear on the product page. Typically coatings is trialled first. Table 5. Application roles of PACM and the property that carries each one. Segment Function of PACM Typical level What decides success Protective coatings curing agent 27-29 phr blush resistance, hardness Adhesives curing agent 28-31 phr colour, bond-line rigidity Composites curing agent 28-41 phr wet-out viscosity, pot life Saturated polyurethane chain extender 125 g per 100 g NCO urea segment regularity Polyamide hardeners amine intermediate set by the adduct amine value of the adduct Figure 3. The five roles listed on the product page, with the property that governs each. Filament winding is the composite case worth checking first, because 50-80 mPa·s wets out roving without solvent yet stays in the bath. For polyamide intermediates the grade is a building block, not a hardener, so the amine value of the finished adduct sets the dosage. 7. Limitations and Material Verification Three limits appear in the first month of use, and none is solved by adding more hardener. 7.1 Known Limitations and Unsuitable Cases No ring methyl groups means the unmethylated alicyclic diamines are the ones that thicken or crystallise in an unheated store. The page publishes no melting point, so the pour point has to come from the COA of the lot before a winter shipment. Cold curing is not its strength. At 10 °C a film still cures, but the surface stays tacky far longer than a DACH or DETA film, and dust becomes the limiting factor. Sections above roughly 50 mm need a slower hardener or a staged ramp; this one alone will crack from exotherm. Food contact, potable water and medical use fall outside the published data, with no migration testing listed. 7.2 Incoming Inspection, Packaging, Storage and Safety A receiving check needs four numbers: APHA colour, viscosity at 25 °C, water by Karl Fischer and purity by the supplier method. Anything outside Table 2 goes back before the drum reaches production. Purity at 99.0% leaves up to 1% of other amines and water, enough to shift colour and pot life between lots. Material ships in drums and keeps at least 12 months from manufacture in the original packing at ambient. Keep the cap closed, away from flame and sunlight, and blanket part-used drums with dry nitrogen. Check with the supplier before blending lots of different dates. The liquid is alkaline and attacks copper alloys, so gloves, goggles and local exhaust are the minimum; the MSDS governs. RoHS and REACH declarations are issued per shipment on request, and nothing here certifies the grade. 8. Frequently Asked Questions What is the amine hydrogen equivalent weight of PACM? It is 52.6 g/eq: 210.36 g/mol divided by four active hydrogens. The page does not print it; the result matches the published 60 g/eq of MACM and 28.5 g/eq of DACH. How much PACM does YLE-128 resin need? YLE-128 at 184-190 g/eq takes 27.7-28.6 phr at full stoichiometry, or 24.9-25.7 phr at a 0.90 index. The exact figure depends on the lot EEW, so the COA value belongs in the formula. Is PACM the same as MACM? No. PACM is unsubstituted at CAS 1761-71-3, AHEW 52.6 g/eq and 50-80 mPa·s; MACM carries two ring methyl groups at CAS 6864-37-5, AHEW 60 g/eq and 80-120 mPa·s. They are not interchangeable by weight. Why does a PACM film blush in humid weather? Primary amines react with carbon dioxide and water to form carbamates at the surface. The reaction runs fastest below 15 °C and above 70% relative humidity, and the haze cannot be washed off with solvent. Can PACM serve as a polyurethane chain extender? Yes. It reacts with isocyanate to build a urea segment, and 100 g of NCO groups take 125.2 g of PACM. Reactivity is high, so prepolymer processes suit it better than one-shot systems. What pot life should be expected at 25 °C? No gel time is published, and none can be calculated from AHEW. Run a 100 g cup test at shop temperature; treat any quoted figure, ours included, as a starting point. 9. Conclusions Light colour, 50-80 mPa·s and a calculated AHEW of 52.6 g/eq put dosage at 27.7-28.6 phr on YLE-128. The value sits in hardness and colour retention at high solids, not cure speed, so DACH stays faster and MACM more storage-tolerant. Two numbers decide most formulations: resin EEW and the index between 0.90 and 1.00. Both can be measured before the drum is opened. 10. References 1. Yolatech product page, PACM (CAS 1761-71-3), https://www.yolatech.com/44-diaminodicyclohexyl-methane-pacm-cas-1761-71-3 (accessed 2026-10-23). 2. Yolatech technical data sheet for PACM, specification and pack size (available on request). 3. Yolatech material safety data sheet for PACM, CAS 1761-71-3 (available on request). 4. ASTM D1652, epoxy content of epoxy resins (EEW). 5. ISO 3001, determination of epoxy equivalent. 6. ISO 9702, amine group nitrogen content of amine epoxide hardeners. 7. ASTM D445, kinematic viscosity. 8. ASTM D1544, Gardner color of transparent liquids. 9. ASTM E203, water content by Karl Fischer titration.

HMDA epoxy curing agent 1,6-hexanediamine (CAS 124-09-4) is an aliphatic diamine hardener sold at 99.90% minimum purity with water below 0.05%. Its calculated amine hydrogen equivalent weight is 29.1 g/eq, and so the stoichiometric demand lands at 15.5 phr in a bisphenol A epoxy resin of 187.0 g/eq. Figure 1. Calculated stoichiometric demand against resin epoxy equivalent weight for HMDA (29.1 g/eq), MXDA (34.0 g/eq) and DETA (20.6 g/eq); curves follow phr = 100 x AHEW / EEW as derived in section 4. 1. Introduction: Where a Short-Chain Diamine Fits Straight-chain aliphatic diamines sit at the fast, high-crosslink-density end of the amine hardener range. 1,6-Hexanediamine is the shortest member that still keeps a flexible C6 spacer between its two primary amine groups, and four active hydrogens per molecule build a tight network at low loading, which is what high-solids coatings and rigid adhesive formulations ask for. The same shortness creates the two practical problems quantified below. A literature melting point of about 41-42 °C, absent from the product page, means drums can wax in a cool warehouse. The strong ammonia odour, stated openly on the product page, rules out indoor work without forced ventilation. Selection depends on whether the formulation accepts those constraints in exchange for reactivity. 2. Materials and Methods: Published Specification of 1,6-Hexanediamine 2.1 Product Identification and Published Specification The grade is sold under the trade name HMDA, chemical name 1,6-hexanediamine, CAS 124-09-4. Four specification items are published on the product page: appearance, purity, water content and the PRI value. Everything else in this report is calculated from structure or marked as literature data, never presented as a published figure. Table 1. Product identification of HMDA, with calculated and literature descriptors marked as such. Item Information Trade name HMDA Chemical name 1,6-Hexanediamine (hexamethylenediamine) CAS No. 124-09-4 Molecular formula C6H16N2 (literature) Active hydrogens per molecule 4, from two primary amine groups (calculated) Amine hydrogen equivalent weight 29.1 g/eq (calculated, 116.2 / 4) Product page yolatech.com/16-hexanediamine-hmda-cas-124-09-4 Table 2. Published specification items on the product page. Property Published value Appearance Colorless to pale yellow liquid Purity, % Min. 99.90 Water, % Max. 0.05 PRI value, mmol/t Max. 100 The liquid appearance on the specification sheet deserves one comment. A diamine that solidifies at about 41-42 °C stays liquid only in warm storage, so check the drum temperature before assuming the contents are pourable. 2.2 Test Methods and Data Sources Three data classes are kept apart. Published values come from the product page and its certificate documents. Calculated values, such as the 29.1 g/eq equivalent weight, follow from the molecular weight of 116.2 g/mol and four active hydrogens, and any reader can recompute them. Literature values, such as the melting point, are labelled as such and should be confirmed against the TDS and MSDS supplied with each lot. Where a formulation example is needed, the resin baseline is the bisphenol A liquid grade YLE-128 with an epoxy equivalent weight of 184-190 g/eq; all arithmetic is performed at the mid-point of 187 g/eq, and every demand figure in section 4 follows the same division. Purity enters as shipped, since the 99.90% floor leaves at most 0.1% for correction, less than normal plant weighing error. 3. Results and Discussion: HMDA Epoxy Curing Agent Against Alternative Polyamines 3.1 Structure-Reactivity Behaviour Two primary amines on a straight C6 chain give four hydrogens of nearly equal reactivity, so gelation arrives early and the exotherm is front-loaded. No steric shielding and no ether oxygen slow the addition, so this diamine reaches handle strength faster than ether-extended adducts at equal loading. The C6 spacer moderates the brittleness short diamines usually cause. Six carbons between the nitrogen nodes let the network deform before it cracks, a small but real gain over ethylene diamine type structures. The gain is relative: against polyetheramines or adducts the film stays harder and less forgiving. Humidity sensitivity is the weak point. The product page states that the material absorbs water and carbon dioxide from air. Carbamate on exposed amine surfaces shows up as blushing and poor intercoat adhesion, so open time in the mixer matters. 3.2 Selection Comparison Table 3 compares the diamine with the polyamine alternatives stocked on the same site, all AHEW values determined by the same molecular-weight division for a fair basis. The choice depends on which constraint binds first: loading accuracy, odour, blush, or flexibility. Table 3. Selection comparison of HMDA with alternative amine hardeners; equivalent weights and phr values are calculated against YLE-128 at 187 g/eq. Attribute HMDA (this grade) Alternative polyamines AHEW, g/eq (calculated) 29.1 DETA 20.6; MXDA 34.0; DMAPA 44.1; MACM 52.6 Stoichiometric phr in YLE-128 15.5 DETA 11.0; MXDA 18.2; DMAPA 23.6; MACM 28.1 Purity floor, % 99.90 (published) DETA high-purity grade; others per their pages Form at 25 °C Solid below about 41-42 °C (literature); liquid when warm MXDA liquid; MACM low-melt solid Odour Very strong ammonia odour (published) Lower for MACM; MXDA sharper but less volatile Blush tendency High in humid air; absorbs CO2 and water (published) MACM lower; DETA also blush-prone Network character Dense and rigid, C6 spacer adds slight flex MXDA aromatic ring raises Tg; DMAPA tertiary N slows cure Read the table by constraint, not by column. If loading accuracy at high purity binds, the 99.90% floor and the 15.5 phr figure make the diamine easy to dose and audit. If blushing or odour binds, pick a cycloaliphatic hardener and accept the higher phr. 4. Formulation and Dosage Calculation The stoichiometric rule is one line: phr = 100 x AHEW / EEW. With AHEW at 29.1 g/eq and the YLE-128 mid-point of 187 g/eq, demand is 100 x 29.1 / 187 = 15.5 phr. Every figure below follows from that division, with no hidden constant. Table 4. Calculated stoichiometric demand of HMDA across three resin grades, with DETA shown for cross-checking. Resin grade EEW, g/eq HMDA phr (calculated) HMDA kg per 100 kg resin DETA phr (calculated) YLE-127 180 16.1 16.1 11.4 YLE-128 187 15.5 15.5 11.0 YLE-170 (BPF) 170 17.1 17.1 12.1 Two corrections sit on top. First, if the lot certificate reports an EEW of 191 g/eq, demand drops to 15.2 phr, so dose from the certificate rather than the datasheet mid-point. Second, under-dosing shows as a tacky surface at room temperature; half a phr of deviation is already visible, which makes this hardener less tolerant of sloppy weighing than higher-AHEW alternatives. 5. Processing Notes and Operating Window Mixing behaviour is unforgiving but predictable. The material wets epoxy resin quickly, the exotherm peaks early in a mass batch, and pot life at bench scale is short once the amine is in. Plan the pour before mixing, not after. Workable practice, distilled from the published properties and the literature melting point: - Warm waxed or solidified drums to 45-50 °C until fully liquid, then homogenise before weighing; unmelted lumps dose badly. - Weigh the amine into the resin within minutes of opening the container. Air exposure builds carbamate skin that later reads as fish eyes in the film. - Keep mixed mass thin during induction when the batch exceeds a few litres; the four-hydrogen structure releases heat fast and a thick pile can discolour. - Ventilate the metering area. The published odour description is not a formality; operators judge leaks by smell long before instruments do. - If a batch must wait, seal the part container with a nitrogen blanket or desiccant, because the water ceiling of 0.05% is easy to exceed through uptake from humid air. Figure 2. Storage temperature scenarios against the literature melting point of about 41-42 °C; bars below the green line mark conditions where drum contents wax or solidify. 6. Applications Fit is best where reactivity and network density pay for themselves and appearance demands are modest. The four segments below all appear as application pages on this site; the table records why the diamine fits or does not. Table 5. Application fit of HMDA by segment. Segment Fit Reasoning Heavy-duty coatings Good with management Dense network resists chemicals; blush control needed in humid shops Structural adhesives Good Fast strength build at 15.5 phr in YLE-128; C6 spacer keeps some flex Composites Conditional Short pot life suits casting and lamination, not long layup schedules Clear decorative coats Poor Odour and carbamate blushing disqualify it where appearance leads Figure 3. Calculated stoichiometric demand of HMDA versus DETA across the three standard resin grades, at the mid-point EEW of each published range. 7. Limitations and Material Verification 7.1 Known Limitations and Unsuitable Uses Say it plainly: this hardener is the wrong choice for water-clear, low-blush finishes, for unventilated indoor work, and for formulations that must sit in an open container for hours. Odour and carbon dioxide uptake rule those uses out regardless of price. Viscosity, epoxy equivalent weight of the amine adduct, and cure kinetics are not published on the product page, so any pot-life or film-property claim beyond the stoichiometry above would be speculation. When those properties matter to a design, request the current TDS and confirm by trial batch; the calculation method in section 4 transfers, but the measured numbers must come from the lot. 7.2 Incoming Inspection, Packaging and Storage A duplicate titration on arrival is cheap insurance. Check purity and water against the certificate; the PRI ceiling of 100 mmol/t flags oxidised amine and is worth a spot check on every new lot. Store drums sealed, off cold floors, above the waxing window in Figure 2. If a drum has solidified, melt once at 45-50 °C and use it soon; repeated melt-solidify cycles waste colour stability and can raise the PRI reading. Packaging and shelf life follow the product page documents. 8. Frequently Asked Questions How much HMDA is needed per 100 parts of bisphenol A epoxy resin? 15.5 phr at a resin EEW of 187 g/eq, calculated as 100 x 29.1 / 187. Dose from the lot certificate EEW when one exists, because a 191 g/eq lot needs 15.2 phr instead. Why has my drum of 1,6-hexanediamine turned solid? The literature melting point is about 41-42 °C, so any storage below that lets the contents crystallise. Warm the sealed drum to 45-50 °C, homogenise, and weigh soon after. Does HMDA cure epoxy faster than DETA? Not faster per equivalent; DETA has the lower AHEW of 20.6 g/eq and gels quickly too. The difference is network density and loading, with HMDA at 15.5 phr against 11.0 phr in the same resin. Can 1,6-hexanediamine be used for clear coatings? Rarely a good idea. Carbon dioxide uptake blushes the film and the ammonia odour needs extraction. Cycloaliphatic hardeners such as MACM serve clear work better. What does the PRI value of 100 mmol/t mean? It is the published ceiling for an oxidation-related index on the specification sheet. A rising PRI reading across lots signals amine oxidation, so track it during incoming inspection. Is the 29.1 g/eq equivalent weight measured or calculated? Calculated, from the molecular weight of 116.2 g/mol and four active hydrogens. It is not a published specification item, and any measured amine value from the certificate takes precedence for dosing. 9. Conclusions As an HMDA epoxy curing agent, 1,6-hexanediamine earns its place where a dense, fast-building network at a modest 15.5 phr matters more than cosmetics. The 99.90% purity floor and 0.05% water ceiling make dosing auditable, and the arithmetic behind every figure in this report is one division a formulator can repeat. Melting behaviour and odour are the two constraints; both are manageable with warmed drums and ventilation, and both argue for cycloaliphatic or adduct hardeners when appearance leads the specification. 10. References 1. Yolatech product page: HMDA, 1,6-Hexanediamine, CAS 124-09-4, https://www.yolatech.com/16-hexanediamine-hmda-cas-124-09-4 2. HMDA technical data sheet, material safety data sheet and certificate of analysis, supplied with each commercial lot. 3. ASTM D1652, standard test practice for epoxy content of epoxy resins, used as the reference basis for resin EEW values. 4. ISO 3001, plastics, epoxy compounds, determination of epoxy equivalent weight. 5. ASTM E203, standard test method for water using volumetric Karl Fischer titration, referenced for the water ceiling.

Liquid phenolic epoxy resin YLEP-631 is a PNE-type novolac grade with 2.7 epoxy groups per molecule. Its published window is an EEW of 168-180 g/eq, a viscosity of 1100-1700 mPa·s at 52 °C and hydrolyzable chlorine below 500 ppm. Seven recurring failure patterns cover most field complaints about it. Figure 1. YLEP-631 pours warm and ships in steel drums; the color sits inside the Gardner limit of 3. 1. Introduction Heat service above 150 °C is the usual reason a formulator leaves a bisphenol A liquid for a novolac epoxy; the same move narrows the process window. YLEP-631 comes from a phenol-formaldehyde novolac glycidylated with epichlorohydrin; the oligomer mixture averages 2.7 epoxide rings per molecule against a fixed two for bisphenol A diglycidyl ether. Diagnosis first. Dosage second. 2. Materials and Methods: Identity and Test Basis for Liquid Phenolic Epoxy Resin YLEP-631 The product page publishes five specification items and a functionality statement; Table 1 sets identity beside them. 2.1 Product Identification and Published Specification Three gaps matter for procurement: no CAS number, density or flash point is published, so transport classification leans on the TDS and MSDS. Table 1. Identity and published specification of YLEP-631. Item Information CAS No. Not published; confirm on the current TDS / MSDS / COA Appearance Colorless to yellowish liquid Color, Gardner 3 maximum EEW, g/eq 168-180 Viscosity 1100-1700 mPa·s at 52 °C Hydrolyzable chlorine, ppm 500 maximum Epoxy functionality 2.7 groups per molecule (as published) Shelf life At least 12 months from manufacture in the original drum 2.2 Test Methods and Data Sources Values in Table 1 are reproduced as published, not re-measured; the lot COA overrides the catalogue window. Epoxy equivalent weight is determined by titration; ASTM D1652 and ISO 3001 describe the two routes in common use. Viscosity is quoted at 52 °C because the grade thickens sharply as it cools; a 25 °C reading is not comparable without a measured curve. Color follows ASTM D1544; hydrolyzable chlorine is a single ceiling, which suits buyers screening lots for ionic contamination. Incoming checks are usually performed in duplicate at two positions in the drum, with a third determination (n = 3) when the pair disagrees. 3. Results and Discussion: Where a 2.7-Functionality Resin Fails Two numbers set the operating window for YLEP-631: 2.7 epoxy groups per molecule and a viscosity specified at 52 °C. 3.1 Structure and the Reactivity Penalty Per kilogram, an EEW of 168-180 g/eq delivers 5.56-5.95 epoxy equivalents; a 184-190 g/eq bisphenol A liquid delivers 5.26-5.43. The gap is 5 to 10 percent. The novolac earns its price elsewhere: 2.7 reactive ends per molecule build network nodes faster than a difunctional resin can, lifting heat deflection and hot wet strength. The same 2.7 ends cause most field failures: more heat per unit mass during cure, less elongation, a shorter margin between workable viscosity and gel. Functionality buys heat resistance with process time. Moisture adds a second penalty: water picked up in a humid storeroom consumes epoxide and feeds the amine blush that spoils thin coatings; drums opened through a coastal summer gel early. 3.2 Field Failure Modes: Symptom, Root Cause, Countermeasure Seven patterns cover most failures reported for systems built on this grade, and each maps to a published number in Table 1. Table 2. Failure modes reported for liquid phenolic epoxy resin YLEP-631 systems. Observed symptom Likely root cause Countermeasure Viscosity creep or gel in a partly used drum Repeated opening in humid air; moisture starts headspace reaction Reseal at once, oldest stock first, re-check at 52 °C Runaway exotherm or char in thick castings 2.7 epoxides per molecule release more heat per unit mass Cast in layers, chill the mould, use a slower amine Cracks or brittle fracture after demoulding High crosslink density, low elongation Blend 20-30 phr of a difunctional liquid, ramp the cure Dry spots on fibre in laminates Bath cooled below the 52 °C reference Hold the bath at 55-60 °C and log it Ionic leakage or copper corrosion Chlorine ceiling is 500 ppm, not zero Screen lot COA; extraction-test the laminate Amine blush or oily film on coatings Moisture condensing on a cold substrate Keep substrate 3 °C above dew point, thin coats Batch color drift in clear parts Gardner 3 maximum allows a wide visual window Agree an internal limit tighter than 3 per lot Two are thermal, two are moisture or stoichiometry errors, the rest storage or specification gaps. Each costs more to fix than the resin. 3.3 Comparison with Alternative Systems Table 3 places YLEP-631 beside four alternatives, using published values only. Table 3. Property comparison of YLEP-631 with alternative epoxy systems (published values). Property YLEP-631 YLEP-638 YLE-128 (DGEBA) YLE-170 (BPF) YLSE-721 EEW, g/eq 168-180 170-190 184-190 160-180 110-125 Form at 25 °C Liquid Semi-solid Liquid Liquid Liquid Viscosity 1100-1700 mPa·s at 52 °C Not published; softening point 36-40 °C 11000-15000 mPa·s at 25 °C 2000-5000 mPa·s at 25 °C 6000-11000 mPa·s at 25 °C Epoxy groups per molecule 2.7 Above 2 2 2 4 YLE-128 bisphenol A epoxy resin stays the reference for room-temperature work: no heating, familiar dosage, two epoxides, a lower heat ceiling. The semi-solid sibling YLEP-638 novolac grade differs in one number: a 36-40 °C softening point instead of a pourable viscosity. YLE-170 bisphenol F resin runs at 2000-5000 mPa·s without warming and shares the 160-180 g/eq bracket but builds a less dense network. YLSE-721 tetrafunctional resin, a glycidylamine at 110-125 g/eq, is the harder-edged route: four epoxides, higher viscosity even at 25 °C, a Gardner allowance of 10. Color is a selection criterion, not a detail, for visible parts. 4. Formulation and Dosage Calculation Stoichiometric hardener demand follows one line, phr being parts per hundred of resin by weight. phr = 100 × AHEW ÷ EEW Table 4 works the equation across the published EEW window. Table 4. Stoichiometric hardener dosage for YLEP-631 across the published EEW window. Hardener Equivalent weight, g/eq phr at EEW 168 phr at EEW 174 phr at EEW 180 DETA (CAS 111-40-0), theoretical AHEW 20.6 12.3 11.8 11.4 MACM (CAS 6864-37-5), published AHEW 60 35.7 34.5 33.3 YLH-9101 (modified amine), published AHEW 92 54.8 52.9 51.1 MHHPA (CAS 25550-51-0), anhydride at ratio 0.85 143.0 85.1 82.2 79.4 Worked example: 2 kg at 174 g/eq takes 100 × 92 ÷ 174 = 52.9 phr of YLH-9101 modified amine, or 1058 g weighed separately. Blends move the target: seventy parts at 174 g/eq with thirty at 170 g/eq give a blend EEW of 172.8 g/eq, and a DETA demand of 11.9 phr. Treat every figure as a starting point: delivered EEW drifts inside its window, and a 10 g error is tolerable in 2 kg but is five percent in a 200 g lab mix. Post-cure belongs in the decision: heat resistance appears only after an elevated-temperature schedule; the current TDS governs the steps. 5. Processing Notes and Operating Window Warming the drum is the first operation, and where most batches go wrong. • Heat indirectly with a water bath or drum heater at 50-60 °C; open flame is out, per the product page. • A 200 L drum needs hours on the heater before the bulk reaches temperature. • Log viscosity at 52 °C against 1100-1700 mPa·s before charging the bath or the mixer. • Weigh resin and hardener by mass, never by volume, and degas 10-15 minutes under vacuum for sections above about 25 mm. • Ramp the cure: hold near 80 °C before climbing to 150-180 °C so the exotherm does not stack. Figure 2. A heater jacket warms the drum for decanting; indirect heat keeps the wall below the reaction point. 6. Applications Six routes appear on the product page, and each spends a different part of the specification. Electronic laminates use the dense network and the 500 ppm chlorine ceiling, watching ionic extraction on fine-line boards. Heat-resistant adhesives take hot strength from the tighter mesh but fail as brittle joints under impact. High-temperature coatings gain chemical resistance after post-cure and lose finish to amine blush on cold substrates. Composites wet out fibre at 1100-1700 mPa·s, but only while the bath holds 55-60 °C. Potting and casting risk exotherm cracking in thick sections; civil engineering grouts and epoxy vinyl inks take chemical resistance from the same network. None runs neat at room temperature; each starts from a warmed bath, a heated substrate or a blend. Figure 3. Wet lay-up shows the 52 °C viscosity first: fabric must be wet out while the bath holds temperature. 7. Limitations and Material Verification 7.1 Known Limitations and Unsuitable Cases This is not the resin for room-temperature hand lay-up, for impact-critical parts, or for flame retardance without additives. The molecule carries neither phosphorus nor bromine; a halogen-free flame-retardant laminate needs a co-resin such as YLDP-320 phenolic flame-retardant resin at 3.0% phosphorus. Viscosity exists only at 52 °C. If your process runs at 25 °C, ask for a measured curve instead of extrapolating. Clear parts need a color agreement tighter than Gardner 3; two compliant lots can look visibly different side by side. 7.2 Incoming Inspection, Packaging, Storage and Safety Incoming inspection should verify EEW by titration against the lot COA, plus color and hydrolyzable chlorine. Reject a lot outside 168-180 g/eq; every dosage moves with it. Storage is standard: well-ventilated, away from flames and direct sunlight, cap closed after use, oldest stock first. Shelf life is at least 12 months in the original drum. Safety information lives in the MSDS. Novolac epoxies are skin sensitisers; gloves and eye protection belong in the written procedure. 8. Frequently Asked Questions Why does a liquid grade need warming before use? YLEP-631 is liquid at 52 °C with 1100-1700 mPa·s, but the novolac backbone thickens sharply as temperature falls. Warming to 50-60 °C restores a workable viscosity. How is the hardener ratio calculated for a 168-180 g/eq novolac? phr = 100 × AHEW ÷ EEW. With MACM cycloaliphatic diamine at AHEW 60 g/eq, 100 g of resin at 174 g/eq takes 34.5 g of hardener. Use the lot COA value, not the catalogue midpoint. What causes cracking in thick YLEP-631 castings? Crosslink density: 2.7 epoxides per molecule build a rigid, low-elongation network, and a thick section adds thermal stress from its own exotherm. Cast in layers, ramp the cure, and consider 20-30 phr of a difunctional liquid. Is 500 ppm hydrolyzable chlorine low enough for electronic laminates? A ceiling, not a guarantee: a lot at 480 ppm passes specification yet may still run high for a fine-line board. Screen each lot COA and extraction-test the laminate when ionic cleanliness is critical. Can YLEP-631 be blended with a bisphenol A resin? Yes, and in practice it usually is. Blending cuts viscosity and cost while the novolac fraction keeps the heat resistance. Recalculate the blend EEW from 100 ÷ (sum of parts ÷ EEW of each) before fixing the hardener weight. Does YLEP-631 provide flame retardance? No. The molecule contains neither bromine nor phosphorus; flame retardance must come from a hardener, a co-resin or an additive, with any RoHS or UL 94 claim verified against current certificates. 9. Conclusions Liquid phenolic epoxy resin YLEP-631 is specified at 168-180 g/eq, 1100-1700 mPa·s at 52 °C, Gardner 3 maximum and 500 ppm hydrolyzable chlorine, with 2.7 epoxy groups per molecule. Its failure history is a history of that functionality: exotherm and brittleness in cure, viscosity and moisture in storage, ionic chlorine in electronics. Used warm, dosed from the lot COA and post-cured on schedule, the grade delivers the heat resistance it is priced for. 10. References 1. Product page, PNE type phenolic epoxy resin YLEP-631, Yolatech: https://www.yolatech.com/pne-type-phenolic-epoxy-resin-ylep-631 (accessed 2026-10-20). 2. Product page, PNE type phenolic epoxy resin YLEP-638, Yolatech: https://www.yolatech.com/pne-type-phenolic-epoxy-resin-ylep-638 (accessed 2026-10-20). 3. Product pages, bisphenol A epoxy resin YLE-127/YLE-128 and bisphenol F epoxy resin YLE-170, Yolatech: https://www.yolatech.com/bisphenol-a-epoxy-resin / https://www.yolatech.com/bisphenol-f-epoxy-resin 4. Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis for YLEP-631, Yolatech (available on request). 5. ASTM D1652 (epoxy content, EEW) with ISO 3001 (epoxy equivalent), together with ASTM D1544 (Gardner color), ASTM D445 (kinematic viscosity) and ASTM E203 (Karl Fischer water).

3,4-Methyl hexahydrophthalic anhydride (MHHPA, CAS 25550-51-0) is a colorless liquid anhydride hardener of 50-80 cps at 25 °C. Assay is 98% minimum, the freezing point sits at or below -15 °C. Dosed at 110 phr in a 130 g/eq alicyclic epoxy, MHHPA yields about 123 mPa·s varnish for coil impregnation. Figure 1. The published appearance of 3,4-methyl hexahydrophthalic anhydride is a colourless liquid, so the hardener is pumped and metered without a melting step. 1. Introduction Dry-type transformer coils, cast insulators and potted semiconductors ask the same thing of a resin: flow into a tight winding, then hold electrical strength at temperature. Anhydride-cured epoxy answers with a slow, low-exotherm cure and an ester network that stays stable when hot. The liquid member of that family, MHHPA runs at 50-80 cps with a freezing point at or below -15 °C. An unheated drum stays pourable through most of a northern winter. The cost sits in the oven. An anhydride does not gel at 25 °C in a useful time; it needs a warm tank and a staged cure. Data come from the MHHPA product page and the resin pages compared here. 2. Materials and Methods: Identity and Specification of Methyl Hexahydrophthalic Anhydride Table 1 reproduces every specification line the page carries for 3,4-methyl hexahydrophthalic anhydride; nothing outside it is treated as a specification. 2.1 Product Identification and Specification Table 1. Identity and published specification of 3,4-methyl hexahydrophthalic anhydride (MHHPA). Item Published value Product name 3,4-Methyl hexahydrophthalic anhydride (MHHPA) CAS No. 25550-51-0 Appearance Colorless liquid Color, Pt-Co Max. 50 Content, % Min. 98 Viscosity, cps at 25 °C 50-80 Freezing point, °C Max. -15 Iodine value, g I2/100 g Max. 1.0 Packaging and shelf life Drums and IBC tanks; 12 months in original packing Storage 5-30 °C, dry, away from oxidants and acids 2.2 Test Methods and Data Sources Three data classes appear here, and a buyer should keep them apart. Page values are the ten lines in Table 1. Calculated values are the anhydride equivalent weight of 168.19 g/eq, from C9H12O3 with one anhydride group, plus every mix viscosity in Table 3. Empirical values, such as the 0.85 factor and accelerator levels, are starting points. Water is determined by Karl Fischer titration according to ASTM E203, and resin epoxy equivalents follow ASTM D1652 or ISO 3001. Flash point is not published; take it from the MSDS, determined according to ASTM D93 or ISO 3679. Every calculated number can be reworked from the equations in section 4. 3. Results and Discussion: Ring-Opening Chemistry and Viscosity MHHPA cures epoxy through an anhydride ring rather than an amine hydrogen, and that difference accounts for the viscosity, pot life and heat resistance compared in Table 2. 3.1 How the Anhydride Ring Opens on an Epoxy Backbone Cure starts from a hydroxyl, not from the hardener. A residual hydroxyl on the epoxy, or a glycol added on purpose, opens the ring into a monoester carrying a free carboxyl. That carboxyl opens an epoxy group into a diester and regenerates a hydroxyl, which opens the next anhydride. The sequence repeats into a polyester network. Two follow. There is no fast amine-epoxy exotherm, so a thick casting does not run away in the mould. And no free amine is left to blush, so clear castings stay clear. In practice an accelerator is still needed: tertiary amines or imidazoles at 0.5-2 phr cut gel time from hours to minutes at 120 °C. That band is an empirical starting point. Overdosing it is the classic mistake. The mix gels in the pot, and the casting yellows. 3.2 Comparison with Amine Hardeners for the Same Alicyclic Resin Against the two amine hardeners used with the same YLCE-2021 alicyclic epoxy, MHHPA asks for more mass but returns a thinner mix. Table 2. MHHPA against two modified cycloaliphatic amine hardeners on YLCE-2021, a 130 g/eq alicyclic epoxy. Property MHHPA YLH-9101 YLH-3002 Hardener type Anhydride Modified amine Modified amine Appearance Colorless liquid Clear pale yellow Transparent viscous Colour limit Pt-Co max. 50 Gardner max. 2 Gardner max. 1 Viscosity at 25 °C 50-80 cps 250-450 cps 5000-12000 cps Mixing basis AEW 168.19 g/eq AHEW 92 g/eq AHEW 182 g/eq phr on YLCE-2021 110 at k = 0.85 70.8 140.0 Mix viscosity, calculated 123 mPa·s 287 mPa·s 1956 mPa·s Gel at 25 °C Not practical Workable Workable Cure heat required Staged oven cycle Ambient possible Ambient possible The mass penalty is real: 110 kg of MHHPA per 100 kg of YLCE-2021 against 70.8 kg of YLH-9101 amine hardener. The viscosity gain is larger: a 123 mPa·s mix fills a winding that a 287 mPa·s mix only wets slowly. YLH-3002 shows the other end: 182 g/eq, 140 kg per 100 kg of the same resin, and a mix near 1956 mPa·s. That is a casting paste, not an impregnation varnish. Colour cannot be read across columns. Pt-Co and Gardner are different scales, and a Gardner 1 is not a Pt-Co 1. If a sheet mixes them, check which scale the limit belongs to. 4. Formulation and Dosage Calculation for Methyl Hexahydrophthalic Anhydride One equation sets the dose, and the only judgement inside it is the 0.85 factor that most casting shops apply to an anhydride-epoxy pair. phr = 100 × AEW ÷ EEW × k, where AEW is the anhydride equivalent weight, EEW the epoxy equivalent weight of the resin, and k the stoichiometric factor. At k = 1.00 the groups balance. At k = 0.85 the mix runs slightly epoxy-rich, which offsets etherification at high temperature and anhydride lost to hydrolysis in an open bath. Table 3. MHHPA requirement for four Yolatech epoxy grades, at full stoichiometry and at the 0.85 working factor. Epoxy grade EEW used Stoichiometric phr phr at k = 0.85 Mix viscosity, calculated YLCE-2021 130 g/eq 129.4 110.0 123 mPa·s YLSE-0600 105 g/eq 160.2 136.2 695 mPa·s YLE-170 170 g/eq 98.9 84.1 567 mPa·s YLE-128 187 g/eq 89.9 76.4 1309 mPa·s Worked example: 100 kg of YLCE-2021 at 130 g/eq carries 769.2 epoxy equivalents, and 110 kg of MHHPA at 168.19 g/eq carries 654.0 anhydride equivalents. The ratio is 0.850; the batch is 210 kg at 52.4% hardener. Mix viscosity comes from a log-mixing rule, log η = Σ w log η, with 65 cps for MHHPA and the midpoint of each resin window. It predicts rather than measures, so confirm on a viscometer at 25 °C. The rule explains the YLE-128 bisphenol A resin row. At 13000 cps it stays near 1309 mPa·s even at 76.4 phr, so that pair belongs in casting, not impregnation. Accelerator goes in last and shifts gel time more than the MHHPA dose does; check with the supplier before fixing a level. 5. Processing Notes and Operating Window Four conditions decide whether a casting comes out clear: moisture, mix temperature, degassing and the oven ramp. • Keep the drum closed between withdrawals; an anhydride takes up water, turns into the diacid and hazes. • Warm resin and hardener to 50-60 °C before mixing, so the blend degasses. • Add MHHPA first, stir without air entrapment, then accelerator. • Degas under vacuum at mix temperature; low viscosity releases air fast and lets fillers settle fast. • Impregnate at 60-80 °C until bubbling stops. Cold varnish on a cold coil is the usual cause of voids. • Gel at 100-120 °C, post-cure at 140-160 °C, and ramp slowly above 20 mm. Figure 2. Coil impregnation is where the 50-80 cps band matters most, because the varnish has to displace air from the winding before gel. 6. Applications of Methyl Hexahydrophthalic Anhydride The published application list is narrow and electrical: coil impregnation, component casting, and sealing of semiconductors such as insulators, capacitors, LED and digital tubes. Table 4. Published application routes for MHHPA and the line check that matters for each. Process route Published fit Line check Coil impregnation Thin varnish wets fine wire Bath viscosity and water Insulator casting Fills thin walls before gel Mould temperature spread Capacitor and LED potting Clear, colour-stable casting Pt-Co of each incoming lot Semiconductor sealing No amine residue to blush Cure completeness by DSC Coating resin intermediate Anhydride for polyester routes Acid value and water Figure 3. Cast insulators and potted components are the visible end use; the Pt-Co limit on the hardener keeps the cast body water-clear. 7. Limitations and Material Verification MHHPA is the wrong hardener for anything that must cure below 100 °C, and its storage window is narrower than the resin it cures. 7.1 Where MHHPA Is the Wrong Choice Ambient-cure flooring, hand lay-up and field repair are out. The chemistry needs an oven, and no accelerator turns it into a 25 °C system with usable pot life. Cold storage is the second trap. Below -15 °C the liquid freezes; remelt at 60 °C or lower with the lid on, because an open drum pulls in water faster than the crystals melt. Low viscosity cuts both ways. Fillers settle overnight, and thin varnish finds every gap in a worn mould. Shelf life is 12 months against 24 for YLCE-2021, so rotate stock; if a drum sat a year, verify water first. 7.2 Incoming Inspection, Packaging, Storage and Safety Each lot should be checked against the COA on four lines: content at 98% minimum, Pt-Co at 50 maximum, viscosity at 50-80 cps at 25 °C, and iodine value at 1.0 maximum. Water has no published limit. Set one from the first COA and run viscosity in duplicate at 25 °C; a single reading on a cold sample misleads. Anhydrides are skin and respiratory sensitisers. Gloves, goggles and ventilation are the minimum, the SDS governs, and spills go to absorbent rather than to a drain. 8. Frequently Asked Questions What dosage of MHHPA should be used with a 130 g/eq alicyclic epoxy? Full stoichiometry gives 129.4 phr; the 0.85 factor gives 110 phr, or 110 kg per 100 kg of YLCE-2021. Recalculate for other resins with phr = 100 × 168.19 ÷ EEW × 0.85. Why does a liquid hardener still need an oven? Because the ring-opening cure is slow at room temperature. A liquid hardener solves metering only; the hydroxyl attack that starts the chain needs heat. Can MHHPA replace a cycloaliphatic amine hardener one for one? No. The dose moves from 70.8 to 110 phr on the same resin, the cure needs heat, and pot life stretches from hours to days. Reformulate the accelerator and the schedule. What does the iodine value limit of 1.0 actually control? It measures residual unsaturation in the ring. A low value means the 3,4-methyl hexahydrophthalic anhydride is fully hydrogenated, so no aromatic chromophore is left to yellow the casting. How should MHHPA be stored, and what happens if it freezes? Drums and IBC tanks at 5-30 °C, dry and sealed, for 12 months. If it freezes, remelt at 60 °C or below with the lid on and mix before use; water pickup during remelt is the real risk. Is MHHPA suitable for room-temperature flooring or hand lay-up? No. Those processes need an ambient-cure amine. MHHPA belongs in heated impregnation, casting and potting lines. 9. Conclusions MHHPA is a colorless liquid anhydride with 50-80 cps at 25 °C, 98% minimum assay, a freezing point at or below -15 °C and an iodine value capped at 1.0. Its 168.19 g/eq sets 110 phr on a 130 g/eq alicyclic epoxy at the 0.85 factor, and the mix lands near 123 mPa·s. That suits heated impregnation, insulator casting and potting. It does not suit room-temperature cure, and it does not rescue a 13000 cps bisphenol A resin. 10. References 1. Yolatech product page: https://www.yolatech.com/34-methyl-hexahydrophthalic-anhydride-cas-no-25550-51-0-mhhpa (accessed 2026-10-19). 2. Yolatech product page for YLCE-2021 alicyclic epoxy: https://www.yolatech.com/34-epoxycyclohexylmethyl-ylce-2021-cas-2386-87-0 (accessed 2026-10-19). 3. Yolatech product page for YLH-9101: https://www.yolatech.com/curing-agnet-ylh-9101 (accessed 2026-10-19). 4. Yolatech product page for YLH-3002: https://www.yolatech.com/curing-agnet-ylh-3002 (accessed 2026-10-19). 5. Yolatech Technical Data Sheet, Material Safety Data Sheet and Certificate of Analysis for MHHPA 25550-51-0 (available on request). 6. ASTM D1652, epoxy content of epoxy resins. 7. ISO 3001, determination of epoxy equivalent. 8. ASTM E203, water content by Karl Fischer titration. 9. ISO 3679, flash point, rapid equilibrium closed cup.