DOPO modified phenolic epoxy resin is a halogen-free reactive flame-retardant resin in which the DOPO unit is chemically bonded into the epoxy backbone. Yolatech now supplies five solution grades with EEW 280-390 g/eq and 70-75% solids for halogen-free copper clad laminates and electrical laminates.   Product Code: YLDP series — YLDP-315-M75 / YLDP-300-K70 / YLDP-310-EK75 / YLDP-300-K75 / YLDP-60-K75Key Raw Material CAS No.: 35948-25-5 (DOPO)Product Category: DOPO Modified Phenolic Epoxy Resin / Halogen-Free Reactive Flame Retardant Epoxy Resin 1. Product Information Item Information Chemical Description Phenolic epoxy resin modified with DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), reacted through the DOPO P-H bond onto the epoxy chain Supplied Grades YLDP-315-M75, YLDP-300-K70, YLDP-310-EK75, YLDP-300-K75, YLDP-60-K75 Key Raw Material CAS No. 35948-25-5 (DOPO) DOPO Molecular Formula C12H9O2P (phosphorus content of the DOPO molecule: approx. 14.3%) Supplied Form Solution-type resin, non-volatile content 70–75±1%, viscosity up to 3000 mPa·s depending on grade Flame Retardant Type Reactive phosphorus-based, halogen-free Family Position One of three DOPO modified phenolic epoxy types from Yolatech, alongside DOPO-HQ modified and DOPO-NQ modified grades Category Halogen-free flame retardant epoxy resin for printed circuit substrates, copper-clad laminates and electrical laminates   2. Product Description DOPO is a rigid cyclic phosphinate whose single P-H bond is what makes it versatile: it adds readily across epoxy groups, double bonds, carbonyls, halogenated sites and amino groups, which is why DOPO has become the standard starting material for reactive phosphorus flame retardancy in electronics. Reacted onto an epoxy backbone, the P-H bond opens the oxirane ring and the phosphorus ends up joined to the polymer through a direct phosphorus–carbon bond. That P–C linkage is the practical difference between a reactive DOPO resin and a phosphorus additive: bonded phosphorus cannot migrate to the surface, cannot be extracted by moisture or solvents, and cannot bloom during lamination. It is also more hydrolytically stable than the P–O–C ester linkages used in many phosphate-based additives, an advantage in laminates that must pass moisture-absorption and CAF testing. In a fire it works two ways at once: condensed-phase char formation insulates the substrate, while gas-phase phosphorus radicals interrupt the combustion chain reaction. No bromine is involved, so no hydrogen bromide is released and smoke density stays lower. Yolatech supplies DOPO modified phenolic epoxy resin as a series of solution-type grades. All five grades are halogen-free flame retardant epoxy resin systems with 70–75% non-volatile content and EEW 280–390 g/eq, sized for varnish preparation and dip-coating lines rather than neat casting. The series shares the property profile the whole family is known for — flame retardancy, heat resistance, low toxicity and low water absorption and expansion coefficient — and sits alongside the DOPO-HQ modified phenolic epoxy resin and DOPO-NQ modified phenolic epoxy resin grades, which carry additional phenolic functionality for higher-Tg requirements.   3. DOPO Modified vs DOPO-HQ vs DOPO-NQ: Choosing the Right Derivative All three family members put phosphorus into the network covalently, but by different chemistry. The base phenolic epoxy resin modified directly with DOPO relies on the P–C bond formed at the oxirane ring; the DOPO-HQ derivative is built on hydroquinone and contributes two phenolic hydroxyl groups; the DOPO-NQ derivative is built on a naphthoquinone core. The table compares the three using grade data published on the respective Yolatech product pages. Comparison Item DOPO Modified (this page) DOPO-HQ Modified DOPO-NQ Modified Phosphorus Bonding Direct P–C bond onto the epoxy chain DOPO-HQ moiety with two phenolic OH groups in the backbone DOPO-NQ moiety on a naphthalene-ring structure Published EEW Range, g/eq 280–390 210–340 300–360 Published N.V. Range, % 70–75 70–80 75 Published Viscosity, mPa·s Up to 3000 (lowest cap in series: <1500) Up to 7000 (lowest cap: <1000) 1000–3000 Distinctive Strength High phosphorus efficiency of the DOPO unit combined with a tight, low-viscosity varnish window Two reactive phenolic sites support higher crosslink density and Tg Naphthalene core supports heat resistance Typical Use Bias Halogen-free copper-clad laminate varnishes and dipping lines High-Tg halogen-free laminates for lead-free assembly Halogen-free laminates where heat resistance is the priority Against a brominated route the comparison is sharper: a brominated epoxy resin or high brominated epoxy resin system typically needs 15–18% bromine in the cured resin to reach UL 94 V-0, while a phosphorus system generally reaches the same rating at approximately 1.5–2.0% phosphorus. That tenfold difference in loading changes the whole formulation balance: less non-structural mass, lower smoke, and no hydrogen bromide.   4. Typical Technical Information The following grade data are the published specification ranges for the DOPO modified phenolic epoxy resin series. Official sales, quotation or technical commitment should be based on company TDS, MSDS, COA or mutually confirmed documents. Grade No. EEW (g/eq) Viscosity (mPa·s) N.V. (%) YLDP-315-M75 295–335 1000–3000 75±1 YLDP-300-K70 280–320 <2000 70±1 YLDP-310-EK75 290–330 <3000 75±1 YLDP-300-K75 280–320 <3000 75±1 YLDP-60-K75 330–390 <1500 70±1   Item Typical Information Flame Retardant Mechanism Reactive phosphorus; condensed-phase char formation combined with gas-phase radical quenching Target P in Cured Laminate Approx. 1.5–2.0% for UL 94 V-0 capability (formulation dependent; confirm the grade phosphorus value from the TDS) Common Curing Systems Dicyandiamide and phenolic novolac cure for laminate prepreg; confirm the curing agent and accelerator package against your own laminate data Storage Store in a well-ventilated area, away from flames and direct sunlight; close the cap tightly immediately after use Shelf Life At least 12 months from the date of manufacture in the original packing at ambient temperatures Safety Documentation All safety information is provided in the Material Safety Data Sheet   5. Formulation Guidance: Grade Selection and Stoichiometry Grade selection in this series is mostly a viscosity-and-solids decision, because the chemistry is shared. Three working rules cover most cases: • For dipping and coating lines that need the lowest viscosity, YLDP-60-K75 (viscosity <1500 mPa·s, EEW 330–390 g/eq) and YLDP-300-K70 (<2000 mPa·s) leave the widest processing window. • For higher build per pass and lower solvent load, the 75% N.V. grades (YLDP-315-M75, YLDP-310-EK75, YLDP-300-K75) deliver more resin per kilogram of varnish than the 70% grades. • For higher crosslink demand, the higher-EEW YLDP-60-K75 shifts the stoichiometry toward more curing agent per 100 parts resin, which raises network density in the cured laminate. Curing agent dosage follows the standard equivalent-weight calculation: phr = AHEW × 100 ÷ EEW Worked example with a mid-series grade at EEW 300 g/eq: against diethylenetriamine (AHEW approx. 20.6 g/eq) the theoretical dosage is 20.6 × 100 ÷ 300 = approx. 6.9 phr. Against dicyandiamide (AHEW approx. 28 g/eq, the workhorse latent cure for copper-clad laminate prepreg) it is 28 × 100 ÷ 300 = approx. 9.3 phr. Compare that with a standard solution-type bisphenol A epoxy resin at EEW 190 g/eq, which needs approx. 14.7 phr of dicyandiamide — the DOPO-modified grade needs less curing agent per unit weight because more of its mass is already resin backbone. Dicyandiamide-cured laminate systems normally run with an accelerator to place the cure window correctly — see the site articles on dicyandiamide epoxy curing agents and on DMP-30 as a curing accelerator. All dosages above are theoretical starting points: verify the actual ratio, gel time and B-stage flow on your own test panels before a production run.   6. Processing Notes • Because the grades are supplied as solutions, varnish preparation is mostly dilution and blending. Add the curing agent only after the resin blend is homogeneous and at the target temperature and solids. • Control varnish temperature during mixing. Viscosity falls with temperature, and a line set up on a cold morning will run differently from the same varnish on a hot afternoon — check viscosity at a fixed reference temperature. • Re-check non-volatile content and viscosity of every incoming batch before use — a fast test that protects the dip-tank from a whole-batch loss. • After any recipe change, re-validate gel time and B-stage flow. Prepreg flow that drifts out of the lamination window is the most common failure mode after a resin-grade switch. • Close container caps tightly immediately after use, and keep drums away from flames and direct sunlight, exactly as the product storage instructions specify.   7. Applications Application Field Function / Description Halogen-Free Flame Retardant Printed Circuit Substrates Reactive phosphorus flame retardancy built into the resin itself, for PCB substrate laminates that must meet halogen-free requirements Electronic Copper-Clad Laminates Varnish-grade resin for CCL impregnation lines; 70–75% N.V. solutions and viscosity caps from <1500 to 3000 mPa·s fit standard dipping and coating equipment Electrical Laminates Insulating laminate sheets and fabricated parts where intrinsic halogen-free flame retardancy, low water absorption and stable expansion coefficient are required The common thread across all three fields: the flame retardant element must survive the whole service life of the board. Because the phosphorus is part of the network, the rating does not depend on an additive that can drift out during lamination, solder reflow or years of thermal cycling. For the wider resin portfolio, the heat resistant epoxy resin family and the multifunctional grades are the usual companions to this series in high-reliability laminate formulations.   8. Frequently Asked Questions What is DOPO modified phenolic epoxy resin? It is a phenolic epoxy resin into which DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, CAS 35948-25-5) has been reacted through its P-H bond, so the phosphorus becomes a covalent part of the polymer backbone. The result is a halogen-free reactive flame retardant resin, supplied here as five solution grades with EEW 280–390 g/eq and 70–75% non-volatile content, used mainly in halogen-free printed circuit substrates, electronic copper-clad laminates and electrical laminates. How is the base DOPO modified grade different from DOPO-HQ and DOPO-NQ modified grades? The base grade bonds phosphorus directly to the epoxy chain through a P–C bond. DOPO-HQ modified grades add two phenolic hydroxyl groups per DOPO-HQ unit, which supports higher crosslink density and Tg in high-Tg laminates, while DOPO-NQ modified grades carry a naphthalene-ring structure oriented toward heat resistance. In published grade data the base series runs EEW 280–390 g/eq at 70–75% N.V., the DOPO-HQ series runs EEW 210–340 g/eq at 70–80% N.V., and the DOPO-NQ series runs EEW 300–360 g/eq at 75% N.V. Which grade should I start with for a copper-clad laminate varnish? Start from your line's viscosity limit and target solids. For the widest low-viscosity window, YLDP-60-K75 (viscosity <1500 mPa·s, EEW 330–390 g/eq) or YLDP-300-K70 (<2000 mPa·s) are the natural starting points. If you want more resin per pass and less solvent to evaporate, choose one of the 75% N.V. grades: YLDP-315-M75, YLDP-310-EK75 or YLDP-300-K75. Confirm the final selection with a trial batch, because prepreg flow and gel time respond to the whole formulation, not to the resin alone. How do I calculate the curing agent dosage for a DOPO modified epoxy? Use the equivalent-weight ratio: phr = AHEW × 100 ÷ EEW. With a grade at EEW 300 g/eq, dicyandiamide (AHEW approx. 28 g/eq) gives a theoretical dosage of approx. 9.3 phr, and diethylenetriamine (AHEW approx. 20.6 g/eq) gives approx. 6.9 phr. These are theoretical values — confirm the practical dosage on your own system together with the accelerator package and cure schedule. Is DOPO modified phenolic epoxy resin truly halogen-free? Yes. The flame retardant element is phosphorus bonded into the resin backbone, not a brominated compound, so the cured laminate contains no added bromine and produces no hydrogen bromide when heated. The family is designed to support halogen-free requirements for printed circuit substrates as an alternative to halogen-containing flame retardants. Compliance documents for a specific shipment should be requested together with the COA. What is the shelf life and how should the resin be stored? The shelf life is at least 12 months from the date of manufacture when stored in the original packing at ambient temperatures. Store in a well-ventilated area, keep away from flames and direct sunlight, and close the cap tightly immediately after use. All safety information is provided in the Material Safety Data Sheet.   9. Packaging, Storage and Safety Packaging: drum package, in accordance with the company delivery arrangement for the order. Storage: at least 12 months from the date of manufacture in the original packing at ambient temperatures. Store in a well-ventilated area, keep away from flames and direct sunlight, and close the cap tightly immediately after use. Safety: all safety information is provided in the Material Safety Data Sheet. Use protective gloves and safety goggles during handling and refer to the MSDS for detailed requirements.

Yolatech YLDP-320 is a DOPO-HQ modified phenolic epoxy resin with 2.9–3.2% phosphorus chemically bonded in the backbone. It delivers halogen-free UL 94 V-0 flame retardancy in high-Tg PCB laminates, electronic encapsulation and advanced composites, and requires no brominated additives such as TBBPA.   Product Code: YLDP-320Key Raw Material CAS No.: 99208-50-1 (DOPO-HQ)Product Category: DOPO-HQ Modified Phenolic Epoxy Resin / Halogen-Free Reactive Flame Retardant Resin 1. Product Information Item Information Chemical Description Phenolic epoxy resin modified with DOPO-HQ (10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) Product Code / Trade Name YLDP-320 Key Raw Material CAS No. 99208-50-1 (DOPO-HQ) DOPO-HQ Molecular Formula C18H13O3P Appearance Light yellow solid Flame Retardant Type Reactive phosphorus-based, halogen-free Category Halogen-free flame retardant epoxy resin for laminates and encapsulation   2. Product Description Conventional flame retardant epoxy systems for PCB laminates rely on brominated chemistry, most commonly TBBPA. Bromine works, but it brings three persistent problems: it adds mass without contributing to the network, it raises smoke density and toxic gas release during combustion, and it sits under continuous regulatory scrutiny in the European Union. As the electronics industry moves toward halogen-free designs, formulators need a flame retardant that is part of the polymer backbone instead of an additive suspended inside it. DOPO-HQ modified phenolic epoxy resin answers that requirement. The DOPO-HQ moiety is built into the resin chain, so it cannot migrate to the surface, cannot be extracted by moisture, and cannot bloom out during lamination. Phosphorus acts through two simultaneous mechanisms: in the condensed phase it promotes char formation and protects the underlying polymer, and in the gas phase it releases phosphorus-containing radicals that quench the combustion chain reaction. The result is a UL 94 V-0 capable system without a single bromine atom. YLDP-320 is the DOPO-HQ modified phenolic epoxy grade in the Yolatech DOPO-modified phenolic epoxy resin series. It carries 2.9–3.2% phosphorus directly in the molecule, which means a formulator can reach the 1.5–2.0% phosphorus level normally required for UL 94 V-0 in the cured laminate without adding a separate flame retardant package. It also keeps the high crosslink density and thermal stability that phenolic epoxy chemistry is known for — the property that matters most when the board has to survive lead-free soldering.   3. Why DOPO-HQ Instead of TBBPA Both routes can reach UL 94 V-0 in an FR-4 equivalent laminate. They reach it very differently, and the differences show up in smoke, dielectric behaviour, regulatory exposure and mass efficiency. If you currently run a high brominated epoxy resin or a brominated epoxy resin system, the table below maps out exactly where a phosphorus route diverges. Comparison Item DOPO-HQ Modified Phenolic Epoxy (YLDP-320) Flame Retardant Element Phosphorus (halogen-free) Typical Loading for UL 94 V-0 Approx. 1.5–2.0% P in the cured resin (formulation dependent) Comparison — TBBPA System Typically requires 15–18% Br in the cured resin to reach the same rating, i.e. a substantially higher additive load Halogen Content None. Fully halogen-free by design. Smoke and Toxic Gas Lower smoke density and lower toxic gas release; no hydrogen bromide formation Regulatory Position Designed to support RoHS and REACH compliance. TBBPA remains under REACH SVHC evaluation and is restricted in some markets. Migration and Blooming Phosphorus is covalently bonded into the network; no migration, no surface blooming, no moisture extraction Crosslink Density and Tg DOPO-HQ contributes phenolic hydroxyl functionality, helping maintain crosslink density and heat resistance in high-Tg systems The practical implication is mass efficiency. A brominated system needs 15–18% bromine in the cured resin to reach V-0. A phosphorus system reaches the same rating at roughly 1.5–2.0% phosphorus. That difference changes the balance of the entire formulation: less non-structural mass, more room for fillers or for resin chemistry chosen on mechanical and dielectric merit rather than on flame retardancy alone.   4. Typical Technical Information The following data are typical values for YLDP-320. Official sales, quotation or technical commitment should be based on company TDS, MSDS, COA or mutually confirmed documents. Item Typical Information Appearance Light yellow solid EEW, g/eq 300–340 Solid content, wt% MIN 99.0 Softening point, °C 70–85 Phosphorus content, % 2.9–3.2 Flame Retardant Mechanism Reactive phosphorus; condensed-phase char formation combined with gas-phase radical quenching Target P in Cured Laminate Approx. 1.5–2.0% for UL 94 V-0 (formulation dependent) Common Curing Systems DICY, phenolic novolac and anhydride systems. Confirm the curing agent and accelerator package against your own laminate data. Transport Information Non-hazardous solid in normal industrial classification. Refer to the actual MSDS for the applicable classification of your shipment.   5. Formulation Guidance: How Much to Use Because YLDP-320 already contains 2.9–3.2% phosphorus, using it as the main resin normally reaches the target flame retardant level without any additional flame retardant additive. When it is blended with a standard bisphenol A epoxy or a conventional phenolic epoxy resin, the blend phosphorus content is a simple weighted average: P(blend) = w1 × P1 + w2 × P2 + … Worked example: a blend of YLDP-320 (3.0% P) and a standard bisphenol A epoxy (0% P). To reach 1.5% P in the cured resin, the YLDP-320 fraction is 1.5 ÷ 3.0 = 50% by weight. To reach 2.0% P, the fraction is 2.0 ÷ 3.0 = approximately 67%. The example is a calculation guide only — verify the actual flame retardant rating on your own laminate, because resin, curing agent, filler and glass content all shift the result. Two formulation notes worth remembering: • Do not simply maximise the DOPO-HQ resin fraction. Unreacted phosphorus groups act as a plasticiser and can pull down Tg and interlayer adhesion. The target is the lowest phosphorus level that still passes V-0, not the highest. • Nitrogen–phosphorus synergy is real. Combining the phosphorus system with a nitrogen-containing co-agent can improve char quality and let you reduce total phosphorus loading.   6. Processing Notes: Dissolution and Cure YLDP-320 is a solid with a softening point of 70–85 °C and is normally dissolved into the varnish together with the other resin components before the curing agent is added. • Keep the dissolution temperature controlled. High temperature held for too long will consume epoxy groups and start the network before the varnish is applied. • Add the curing agent only after the resin is fully dissolved and the varnish is homogeneous and at the target temperature. • Watch gel time after a recipe change. Increasing the DOPO-HQ fraction changes the reactivity balance, and prepreg flow can fall out of the lamination window if gel time is not re-checked. • Verify each incoming batch with a simple gel time test and a visual clarity check before scaling up. It is a ten-minute test that prevents a production batch loss.   7. Applications Application Field Function / Description Halogen-Free PCB Laminates High-Tg halogen-free FR-4 equivalent laminates for lead-free assembly, servers, communications equipment and automotive electronics Electronic Encapsulation Potting and encapsulation compounds requiring permanent, non-migrating flame retardancy together with electrical insulation High-Performance Composites Halogen-free prepreg and structural composites for aerospace, rail and automotive interiors where smoke and toxicity limits apply Electrical Insulation Dry-type transformer and high-voltage insulation systems needing intrinsic halogen-free flame retardancy that survives long-term thermal ageing Powder Coatings Reactive flame retardant component in epoxy powder coating formulations   8. Frequently Asked Questions What is the phosphorus content of YLDP-320? YLDP-320 contains 2.9–3.2% phosphorus by weight. For comparison, the DOPO-HQ raw material itself contains approximately 9.6% phosphorus. Because YLDP-320 is a resin with the DOPO-HQ structure built into the polymer chain, the phosphorus is available to the cured network as a reactive component rather than as a dispersed additive. Can DOPO-HQ modified epoxy replace TBBPA in an FR-4 laminate? Yes, and it does so with a much lower loading. A brominated system typically needs 15–18% bromine in the cured resin to reach UL 94 V-0, whereas a phosphorus system typically reaches the same rating at approximately 1.5–2.0% phosphorus. The substitution is not a drop-in one-for-one swap: the resin ratio, curing agent, accelerator and gel time all need to be re-balanced and re-validated on your own test panels. What Tg can be expected from a DOPO-HQ laminate? Formulated systems based on DOPO-HQ modified phenolic epoxy are used in high-Tg laminates for lead-free soldering, where the usual requirement is a Tg above 170 °C. The actual value depends on the blend ratio, the curing agent, the filler and the cure schedule, so it must be confirmed against your own formulation. YLDP-320 is solid with a softening point of 70–85 °C, which leaves a practical processing window for varnish preparation. What is the difference between DOPO and DOPO-HQ? DOPO is the base molecule, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, with a single reactive P-H bond and a phosphorus content around 14.3%. DOPO-HQ is the hydroquinone derivative, with two phenolic hydroxyl groups and a phosphorus content around 9.6%, which gives it two reactive sites and improved crosslink density for high-Tg systems. Yolatech also supplies DOPO modified phenolic epoxy resin and DOPO-NQ modified phenolic epoxy resin so that a formulator can select the derivative that matches the target Tg and loading. Is YLDP-320 RoHS and REACH compliant? YLDP-320 is halogen-free and is designed to support RoHS and REACH compliance in the finished article. It contains no TBBPA and no brominated flame retardant. Regulatory status must always be confirmed against the latest official text, and the compliance documents for a specific shipment should be requested with the COA. How should DOPO-HQ epoxy be stored? Keep the product tightly sealed in a cool, dry and well-ventilated place, away from heat, direct sunlight and moisture. DOPO-derived materials are moisture sensitive, so an opened container should be re-sealed promptly. Refer to the MSDS for detailed handling requirements.   9. Packaging, Storage and Safety Packaging: usually available in bags or drums in accordance with supplier specifications. Actual packaging should follow the company delivery arrangement for the order. Storage: keep tightly sealed in a cool, dry and well-ventilated place. Avoid heat, direct sunlight and moisture ingress. Keep away from strong oxidizing agents, strong acids and incompatible materials. Safety: use protective gloves, safety goggles and protective clothing during handling. Avoid inhalation of dust. Refer to the MSDS for detailed safety information.