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.