Research Progress on Flame-Retardant Epoxy Resins And Their Composite Materials

Research Progress on Flame-Retardant Epoxy Resins and Their Composite Materials

As an advanced composite material resin matrix, epoxy resin is currently widely used in various fields such as aerospace, electronics, and automotive manufacturing. Epoxy resin is a high-performance synthetic resin that, after curing, exhibits excellent mechanical properties, adhesive properties, electrical properties, and electrical insulation properties. Additionally, it has good chemical stability, dimensional stability, ease of processing, stress transfer properties, and low cost. However, due to the molecular structure characteristics of epoxy resin, its flame-retardant properties are poor, and it is prone to ignition and combustion under the influence of flames. The oxygen index (LOI) of general-purpose epoxy resin is approximately 19.8%, making it a flammable material. To enhance its fire safety and expand its application scope, flame-retardant modification is necessary.

I. Flame-Retardant Epoxy Resin

The flame-retardant modification methods for epoxy resins can be categorized into three types: additive-based, reactive-based, and nano-flame-retardant-based. Among these, the additive-based flame-retardant method involves physically incorporating various flame-retardant additives that do not participate in the curing reaction into the epoxy resin to impart flame-retardant properties. The reactive-based flame-retardant method involves introducing flame-retardant elements such as halogens, P, Si, or N into the epoxy system through chemical reactions to achieve flame-retardant effects. Nano-flame retardant methods utilize the high reactivity of nano-particles and their tendency to undergo physical or chemical interactions with certain functional groups in epoxy resins to improve the mechanical properties of epoxy composites while further enhancing their flame retardant performance.

1. Additive-based flame retardant methods

• Halogen-based flame retardants

Halogen-based (bromine-based and chlorine-based) flame retardants are widely used due to their excellent flame-retardant effects. Adding a small amount of halogen-based flame retardants, especially bromine-based flame retardants, can significantly enhance the flame-retardant properties of epoxy resins. Bromine-based flame retardants primarily include decabromodiphenyl ether, tetrabromobisphenol A, dibromononyl glycol, and tetrabromophthalic anhydride. These flame retardants exhibit good compatibility with epoxy resin systems and are typically used in conjunction with antimony trioxide to synergistically enhance the flame retardancy of epoxy resins, yielding excellent flame retardancy. However, a major drawback of bromine-based flame retardants is that they decompose during combustion, releasing smoke, toxic gases, and corrosive gases harmful to human health and the environment. Consequently, environmental safety concerns associated with halogenated flame retardants have garnered widespread attention, leading to a series of studies and the development of phosphorus-based flame retardants and synergistic flame retardants combining phosphorus, silicon, and nitrogen as alternatives to halogenated flame retardants.

• Phosphorus-based flame retardants

Red phosphorus, phosphoric acid (salt) esters, ammonium polyphosphate, and alkyl phosphoric acid (salt) are added as phosphorus-containing flame retardants to epoxy resins, all of which exhibit excellent flame retardant effects. In different epoxy resin curing systems, when the phosphorus content reaches 2 wt% to 5 wt%, the flame retardant performance can achieve the UL-94 V-0 rating, and the oxygen index is significantly improved. Most phosphates are liquids, which have poor compatibility, poor heat resistance, and high volatility. Their addition adversely affects the mechanical properties and heat resistance of epoxy resins. For example, phosphates (salts) significantly lower the glass transition temperature of epoxy resins.

As inorganic phosphorus-based additive flame retardants, red phosphorus, ammonium polyphosphate, and phosphates are widely used. Red phosphorus exhibits high-efficiency, low-toxicity, and smoke-suppressing flame-retardant effects, making it an excellent flame retardant. However, its drawbacks include susceptibility to oxidation, moisture absorption, and the potential for dust explosions, limiting its application. Encapsulating red phosphorus is the most effective method to address these drawbacks. Table 1 lists the influence of phosphorus content on the flame-retardant performance of the epoxy resin system in the coated red phosphorus flame-retardant epoxy resin system.

Additive phosphorus-based flame retardants, including ammonium phosphate, polyphosphoric acid ammonium, and their corresponding intumescent flame retardants, have garnered increasing attention from researchers. Long-chain polyphosphoric acid ammonium salts possess high P-N flame-retardant element content and excellent thermal stability. Their nearly neutral nature allows them to be used in combination with other substances, making them a promising alternative to halogen-based flame retardants. Table 2 lists the LOL values of polyamide-cured epoxy resin systems under different polyphosphoric acid ammonium salt (APP) addition levels.

• Inorganic flame retardants

The most commonly used inorganic flame retardants for preparing halogen-free flame-retardant epoxy resins include metal oxides (such as aluminum hydroxide and magnesium hydroxide), borides (such as zinc borate), and nitrogen-containing flame retardants.

As the most widely used inorganic flame retardant, aluminum hydroxide [AI(OH)] (ATH) offers stable performance, flame retardancy, smoke suppression, low cost, and is non-toxic and harmless. In terms of thermal decomposition, ATH exhibits flame retardant compatibility with epoxy resin-based composites, losing crystalline water in a zero-order reaction to form active aluminum oxide, thereby enhancing the flame retardant properties of the epoxy resin-based composite. However, the issue is that only when a significant amount of aluminum hydroxide is added can moderate flame-retardant performance be achieved. When Xiao Weidong et al. added 60 parts of aluminum hydroxide to flame-retardant epoxy resin, the oxygen index reached 27.6%. Over-filling inevitably leads to poor flowability during resin mixing and molding, resulting in reduced processing and mechanical properties of the material. To achieve flame retardancy without compromising other material properties, the superfine surface treatment technology of this flame retardant has become a hot topic in current flame retardant technology development.

As a new type of flame retardant, zinc borate flame retardant exhibits excellent performance, featuring good thermal stability, low bulk density, fine particle size, easy dispersion, and non-toxicity. At temperatures above 300°C, zinc borate can lose its crystallization water, exhibiting endothermic and cooling effects. The mechanism by which zinc borate enhances the flame retardancy of epoxy resin is that approximately 38% of the zinc in zinc borate enters the gas phase in the form of zinc oxide or zinc hydroxide, diluting flammable gases and reducing combustion rates, thereby improving flame retardancy. A. DeFenzo et al. investigated the effect of zinc borate (ZB) on the flame retardant performance of epoxy resin. As shown in Table 3, after modification with zinc borate, the ignition time of the epoxy resin was prolonged, and the heat release was significantly reduced. Other studies have shown that the particle size distribution of zinc borate has a significant impact on the mechanical properties, applicability, and appearance of the material. When used in combination with traditional flame retardants, it can significantly improve the flame retardant and smoke suppression performance of the epoxy system.

Inorganic nitrogen-based flame retardants are primarily triazine compounds, specifically melamine and its salts, including phosphates, cyanuric acid salts, dicyandiamide salts, and guanidine salts, among others. These are typically used as components of mixed intumescent flame retardants in flame-retardant epoxy resin systems.

• Silicon-based flame retardants

Silicon-based flame retardants primarily include silica, layered silicate nanomaterials, siloxane, and siloxane compounds. Silicon-based flame retardants can stabilize the char layer, but silicon flame retardants alone cannot achieve good flame retardant effects in epoxy systems and generally need to be used in combination with other flame retardants. Among these, siloxanes and phosphorus-containing flame retardants can achieve good synergistic flame retardant effects.

2. Reactive flame retardant method

The reactive flame retardant method refers to the design of the molecular structure of epoxy resin and its curing agent to incorporate flame retardant elements into the macromolecular chain of the epoxy resin. This is achieved by introducing inorganic element groups containing halogens, nitrogen, phosphorus, silicon, and other elements with flame retardant properties, thereby enhancing the inherent flame retardant effectiveness of the epoxy resin. While providing sustained flame-retardant performance, the reactive flame-retardant method maximizes the retention of the epoxy resin's original mechanical and thermal properties, without affecting its subsequent processing or application.

• Structural flame-retardant epoxy resin

Structural flame-retardant epoxy resin refers to methods that introduce flame-retardant elements into the epoxy resin molecular chain to impart flame-retardant properties to the epoxy system, such as halogen-containing epoxy resin, phosphorus-containing epoxy resin, nitrogen-containing epoxy resin, and silicon-containing epoxy resin. Halogen-containing epoxy resins are primarily synthesized using halogen-containing monomer raw materials (such as phenols), including brominated bisphenol A-type epoxy resins and fluorinated epoxy resins, with brominated bisphenol A-type epoxy resins being the most commonly used. Brominated bisphenol A-type epoxy resins are pale yellow to amber-colored viscous liquids or solids. Brominated epoxy resins exhibit excellent chemical stability, superior electrical insulation properties, strong adhesion, low toxicity, high heat distortion temperature, and flame-retardant properties.

The primary method for introducing phosphorus-containing groups into epoxy resins involves utilizing the active groups of phosphorus-containing compounds to react with the epoxy groups or active epoxy oxides of the resin through an opening reaction. This process introduces phosphorus into the epoxy resin system based on its related components. The cured products of phosphorus-containing epoxy resins exhibit excellent thermal stability and flame retardancy during combustion because the phosphoric acid forms a protective layer over the carbon layer, which resists oxidation.

Researchers introduced a novel N/P/S-containing flame retardant (HBD) into epoxy resin composites, resulting in an epoxy resin (EP) with excellent flame retardancy, good transparency, and good thermal stability. When the phosphorus content was 0.48 wt%, EP/HBD achieved a V-0 rating with a limiting oxygen index of 33.5%. Cone calorimeter (CC) tests showed that compared to EP, the addition of HBD increased the ignition time by 1.5 times, reduced the maximum heat release rate by 50%, reduced the total heat release by 40%, and reduced the total smoke generation by 50.7%. Additionally, the flame retardant performance of EP/8%HBD was significantly superior to that of similar P/N/S flame retardant-modified EP materials reported in the literature. Mechanistic analysis indicates that the phosphorus element in the flame retardant plays a crucial role in the flame retardant process, while HBD plays a significant role in the formation of a dense expanded carbon layer and gas-phase extinction.

Researchers synthesized phosphorus-containing epoxy resins by copolymerizing DOPO derivatives containing dihydroxy groups with epoxy resins, and investigated the effect of phosphorus content on the flame retardant performance of the epoxy/DDS curing system. The results showed that the flame-retardant performance of the epoxy system increased with the increase in phosphorus content in the system. When the phosphorus content reached 1.5%, the system's LOI reached 36%, and the self-extinguishing performance reached V-0 grade, demonstrating excellent flame-retardant performance. Further increasing the phosphorus content did not result in a significant increase in the system's LOI value. Thermal release studies showed that the peak thermal release rate of EP-0 was 1182.93 kW/m², while that of EP-1.5 was 792.19 kW/m², a 33% decrease compared to EP-0. Xianshuang et al. prepared a cyclic tris(phosphine) macromolecular flame retardant containing phosphine and phosphine-substituted phenyl groups, hexa-[4-(N-cyclohexyl-DOPO-methylene)phenoxy]cyclotris(phosphine) (M-CTP), and analyzed its flame retardant performance and thermal stability in flame-retardant epoxy resin cured products. The results showed that when the addition of M-CTP in the flame-retardant epoxy resin curing product was 20 g and the phosphorus content was 1.4%, its flame-retardant performance could reach UL94 V-0 grade, with a LOI value of 34.6%. M-CTP exhibits excellent flame-retardant effects on epoxy resins. During combustion, the phosphonitrile residues facilitate cross-linking into carbon, while the element promotes the generation of non-flammable gases, effectively reducing the release of heat and smoke during the combustion process of the epoxy resin curing product. Introducing silicon elements into the epoxy resin molecules enables the resin to maintain excellent thermal stability while significantly improving its flame-retardant properties. Silicon-containing epoxy resins are primarily synthesized through the reaction of active siloxanes containing hydroxyl or amino groups with epoxy compounds. The introduction of silicon elements effectively enhances the material's thermal-oxidative stability and char formation rate.

Researchers blended two types of polyhedral oligomeric siloxanes (POSS) with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based organic phosphorus flame retardants (D-bp) to prepare phosphorus-silicon synergistic flame-retardant epoxy resins, and analyzed their flame-retardant properties. The results showed that even at a phosphorus content of only 0.25%, the phosphorus-silicon synergistic flame-retardant epoxy resin could achieve UL94V-0 rating. When epoxy-POSS was blended with D-bp, it could simultaneously improve the flame-retardant, thermal, mechanical, and dynamic mechanical properties of the phosphorus-silicon synergistic flame-retardant epoxy resin, demonstrating excellent comprehensive performance. Mercado et al. prepared epoxy resins with different silicon contents using silicon-containing epoxides or silicon-containing prepolymers as raw materials, cured with diaminodiphenylmethane (DDM). The study found that the introduction of silicon significantly improved the flame-retardant properties of the cured material. As the silicon content increases, both the maximum weight loss temperature and char residue of the epoxy resin are significantly improved, regardless of whether the curing is conducted in a nitrogen atmosphere or in air. The limiting oxygen index (LOI) value increases with the silicon content, with the LOI value of 1,4-diphenylglycidyl methacrylate (BGDMSB) reaching 33.5%.

• Structural Flame-Retardant Epoxy Resin Curing Agent

The development of various new flame-retardant curing agents is achieved by introducing flame-retardant chemical elements (halogens, phosphorus, nitrogen, silicon, etc.) into the molecular structure of ordinary epoxy curing agents. Currently, the main types of flame-retardant epoxy resin curing agents include tetrabromophthalic anhydride, dichlorosuccinic anhydride, phosphoric acid containing amine groups and its amides, phosphine amines, and amine curing agents containing silicon.

Introducing phosphorus-containing groups into the molecular structure of the curing agent enhances the flame retardancy and thermal stability of the cured epoxy resin system. Research on phosphorus-containing flame-retardant epoxy resin curing agents has primarily focused on phosphorus-containing amine curing agents, phosphorus-containing anhydride curing agents, phosphorus-containing linear phenolic curing agents, phosphorus-containing amine curing agents, and phosphorus-containing phosphate curing agents. Chen et al. used melamine phosphate (MP) as a curing agent for bisphenol A epoxy resin, with the DDM/EP system cured with 4,4'-diaminobenzene (DDM) as the control sample. The results showed that the weight loss temperatures of epoxy resins cured with MP at 5% and 10% were 264.1°C and 306.7°C, respectively, while those of epoxy resins cured with DDM at 5% and 10% were 372.4°C and 378.9°C, respectively. The MP system decomposed before the epoxy resin decomposed. The oxygen index of MP-cured epoxy resin was 29%–34%, while that of DDM-cured resin is 19%. The flame retardancy of MP-cured epoxy resin is significantly improved. Hsiue et al. used three amino-terminated silicone compounds—amino-terminated polydimethylsiloxane (AS), di(p-aminophenoxy)dimethylsilane (DS), and 1,3-di(3-aminopropyl)1,1,3, 3-tetramethylbisiloxane (TS) as curing agents to cure epoxy resin. Compared with resin cured using the conventional curing agent DDM, the modified system exhibited a significant increase in glass transition temperature (Tg).

Researchers used amino-terminated polydimethylsiloxane (AS), di(4-aminophenoxy)dimethylsilane (DS), and 1,3-di(3-aminopropyl) 1.1.3.3-tetramethylbisiloxane (TS) as curing agents to cure epoxy resins. When compared with resins cured using the conventional curing agent DDM, it was found that the modified system exhibited a significant increase in glass transition temperature (Tg). (DDM: 220.1°C, TS: 277.8°C, DS: 276.6°C, AS: 295.0°C). Additionally, the oxygen index of the modified resin system reached 31%–34%, demonstrating excellent flame-retardant properties.

• Nano-scale flame retardant methods

The three main methods for preparing epoxy resin nano-scale flame-retardant composite materials include the blending and dispersion composite method, the intercalation composite method, and the nano-film method. Common nano-scale flame retardants include layered nano-clays, nano-silica, silicon carbide, nano-metal oxides, nano-silanes (POSS), carbon nanofibers, carbon nanotubes, expanded graphite, and fullerenes.

Researchers used expanded flame retardant (IFR) as the primary flame retardant and KH570-modified nano-silica (SiO₂-g-KH570) as a synergist to prepare flame-retardant epoxy resin materials. The oxygen index (LOI) of the EP/IFR/SiO₂-g-KH570 system was 30.2%, and passed the UL-94 test at the V-0 level. Electron microscope analysis of the char residue morphology indicated that the EP/IFR/SiO₂–KH₅₇₀ system could form a more dense and continuous carbon layer, providing an effective physical barrier and demonstrating excellent flame-retardant performance.

Researchers found that the flame-retardant performance of the epoxy/SiO₂ nanocomposite is directly related to the Si content. When the silicon content in the composite is below 8.73%, the oxygen index increases with the increase in SiO₂. However, when the SiO₂ content reaches a certain level, the increase in the oxygen index becomes significantly less pronounced. The flame retardant properties of epoxy resin/SiO₂ nanocomposites are shown in Table 4.

II. Flame-retardant epoxy resin-based composite materials

1. Halogen-antimony flame-retardant epoxy resin composite materials

The halogen-antimony synergistic flame-retardant system, due to its low cost and high flame-retardant efficiency, remains the most common and widely used flame-retardant system in epoxy resin-based structural flame-retardant composite materials. Researchers employed a bromine-antimony synergistic method to prepare the flame-retardant toughened epoxy resin KHFR-A and investigated the properties of the resin matrix and glass fiber fabric-reinforced composite materials. The specific properties are shown in Tables 5.

2.Additive phosphorus-based flame retardant epoxy resin composite material

Currently, the most commonly used additive-type phosphorus-based flame-retardant epoxy resin composites include phosphate ester flame-retardant epoxy resin composites, red phosphorus (coated red phosphorus) flame-retardant epoxy resin composites, and ammonium polyphosphate (APP) flame-retardant epoxy resin composites. Among these, APP is highly favored due to its high efficiency, low toxicity, and excellent cost-effectiveness. Researchers investigated the effects of APP on the flame-retardant properties and mechanical properties of epoxy/glass fiber composites, with a particular focus on how different heat fluxes affect the mechanical properties of the composites after exposure to fire. The results are shown in Tables 6 and 8. The mechanical property study results indicate that after flame-retardant modification, the bending strength of the epoxy/glass fiber composites slightly increased, but the bending modulus significantly decreased. under low heat flux (20 kW/m²), the performance retention rate of the composite material improved, but as the heat flux increased, the material's performance showed a significant decline trend. The results of the flame-retardant performance study indicated that after modification with 7.5% APP, the peak heat release rate of the composite material decreased by 73%, the total heat release decreased by 20%, and the char residue rate increased by 13%, with a significant improvement in flame-retardant performance.

3. Reactive phosphorus-based flame-retardant epoxy resin composites

Reactive phosphorus-based flame-retardant epoxy resin composites are currently a hot research topic, with research efforts primarily focused on the development of new phosphorus-containing epoxy resins and curing agents, as well as their impact on composite material performance. Among these, phosphorus-containing amine-type curing agents and DOPO-modified epoxy resin systems show the most promising application prospects in the field of structural flame-retardant composites.

Researchers synthesized a phosphorus-containing active amine curing agent, TEDAP, and compared its effects on the performance of carbon fiber-reinforced epoxy resin composites, as detailed in Tables 8 and 9. As shown in the tables, the use of phosphorus-containing active amine curing agents significantly improves the flame-retardant properties of composites but simultaneously causes a substantial decline in their mechanical properties.

Research has demonstrated that the use of phosphorus-containing amine curing agents (TEDAP) to cure epoxy resins can effectively improve the flame-retardant properties of hemp fiber-reinforced epoxy composite materials. The system's LOI, heat release, and smoke release properties all show significant improvements. However, the use of phosphorus-containing curing agents also results in a noticeable decline in the mechanical properties of the composite materials, with tensile strength decreasing by 16.8% and flexural strength decreasing by 25.6%.

Researchers investigated the effect of DOPO reactive flame retardants on the properties of epoxy/carbon fiber composites. The results showed that after DOPO modification, the glass transition temperature and interlaminar shear strength of the composite decreased by 11.6% and 9.0%, respectively, while the interlaminar toughness remained largely unchanged, and the flame retardant performance of the material was significantly improved.

4. Performance of halogen-free synergistic flame retardant epoxy resin composite materials

To enhance the flame-retardant efficiency of halogen-free flame-retardant epoxy systems, synergistic flame-retardant methods are commonly employed. By adjusting the ratio of flame-retardant elements, an optimal flame-retardant effect can be achieved. Currently, the most commonly used halogen-free synergistic flame retardant method for flame-retardant epoxy resin composites is the nitrogen-phosphorus synergistic flame retardant method. Table 10 lists the properties of nitrogen-phosphorus synergistic flame-retardant glass fiber/epoxy composites. As shown in the table, epoxy composites treated with nitrogen-phosphorus synergistic flame retardants exhibit excellent mechanical properties, self-extinguishing properties, and fire resistance, with low smoke density. However, the issue of high heat release still requires further resolution.

5. Epoxy Resin Nano-Flammable Composite Materials

Since the effectiveness of flame retardancy is governed by chemical reactions, the smaller the particle size and the larger the specific surface area of an equal amount of flame retardant, the better the flame retardant effect. Additionally, the nano effect can simultaneously improve the material's mechanical properties and heat resistance. Epoxy resin nano-flammable composite materials have always been a hot topic of research. Numerous studies have focused on using nanotechnology to enhance the flame retardant efficiency of materials while balancing their flame retardant, thermal resistance, and mechanical properties.

Researchers modified a bisphenol A epoxy system cured with triethyl tetramine using layered double hydroxide (LDH) nanomaterials and investigated the effect of LDH addition on the mechanical properties and flame retardancy of the epoxy nanocomposite. The results indicated that an appropriate LDH addition amount promotes improvements in both mechanical and flame-retardant properties. However, using LDH nano-flame retardants alone cannot achieve good flame-retardant performance (V-0).

When used in combination with traditional flame retardants, nano-flame retardants can achieve synergistic flame retardant effects. It has been reported that nano-clays can effectively improve the mechanical properties and flame retardant properties of phosphorus-containing flame retardant epoxy resin composite systems. Specific data are shown in Tables 11 and 13. As shown in the tables, adding 3% nano-clay to an epoxy system with 1% phosphorus content can achieve good synergistic flame retardant effects in the composite material.

III.Application Trends of Flame-Retardant Epoxy Resin-Based Composite Materials  

In recent years, with the rapid development and growing demand in the aerospace industry, a few manufacturers in Europe and the United States have developed lightweight, high-toughness, and flame-retardant modified epoxy resin matrices using different resin systems, as well as a series of prepreg products made with various types of fibers as reinforcing materials. These products have been widely applied in the manufacturing of internal components for large aircraft fuselages. Major suppliers of flame-retardant epoxy prepregs abroad include companies such as Hexcel, Cytec, Park, and Gurit. Hexcel's glass fiber-reinforced flame-retardant epoxy resin prepregs are primarily used for fire-resistant components such as engine cowlings, firewalls, floors, aircraft side panels, kitchens, ceilings, and bathrooms. Cytec's series of flame-retardant epoxy prepregs feature excellent mechanical properties and flame-retardant performance and have been applied in aircraft such as Airbus.

Gurit has developed a series of flame-retardant epoxy prepregs for different operating temperatures and has also developed a flame-retardant epoxy prepreg EP137-03-40 with ultra-low smoke density to meet low-smoke requirements, with a maximum smoke density D4 of 60 at 4 minutes. Park Advanced Composite Materials has also developed two series of flame-retardant epoxy composite materials with excellent self-extinguishing properties: E-761 and E-766B. The E-761 prepreg features various reinforcing fabric forms, including E-glass fiber fabric, carbon fiber fabric, quartz fabric, and aramid fiber fabric, and can meet the requirements for aircraft interiors, secondary load-bearing structures, and sandwich structure panels.

Major domestic manufacturers of flame-retardant epoxy prepregs include the Beijing Aerospace Materials Research Institute, China Aviation Composite Materials Co., Ltd., and the Jinan Special Structures Research Institute. Domestic research and development of structural flame-retardant epoxy composite materials began in the 1980s, with the subsequent development of flame-retardant epoxy structural materials such as 3218Z, 3233, 3242, and 3218-2. These materials exhibit excellent flame-retardant properties and have a long-term service temperature range of -55°C to 100°C. The EW-60/FBG-2-10 low-dielectric-constant flame-retardant glass fiber fabric epoxy resin-based composite material exhibits outstanding fracture toughness, flame-retardant properties, environmental resistance, and dielectric performance, and can operate continuously at 110°C.

IV. Conclusions  

Under the theme of environmental protection, the development of flame-retardant epoxy resin-based composite materials has been moving toward halogen-free and systematic approaches, primarily in the following areas:  

1. Traditional flame retardants such as phosphorus and nitrogen will continue to be improved and their potential flame-retardant properties further explored.  

2. From a molecular level perspective, research and development efforts on reactive flame-retardant epoxy resins will be intensified through rational design, structural optimization, and controlled synthesis.

3. By deeply studying the combustion mechanisms of epoxy resin composites, new flame-retardant pathways will be developed.  

4. Synergistic flame-retardant systems will be fully developed, with composite flame-retardant optimization of phosphorus-nitrogen, nitrogen-silicon, phosphorus-silicon, and nanoparticles to achieve optimal effects. Synthesis processes will be simplified, production costs reduced, and the industrialization and commercialization processes accelerated.

The innovative research and development achievements of YINSU Flame Retardant in the field of epoxy resin include a variety of solutions such as brominated epoxy, epoxy resin red phosphorus paste and bromine antimony flame retardant. These highly efficient flame retardants not only provide excellent flame retardant properties, but also effectively improve the processability and high temperature resistance of epoxy resin, and are widely used in electronics, electrical and other high-demand fields. We are committed to providing customers with customized flame retardant solutions to help improve product safety and market competitiveness.