Flame-retardant epoxy resin composition and preparation method therefor, prepreg and composite material

Abstract

The present invention relates to the technical field of epoxy resins, and provides a flame-retardant epoxy resin composition and a preparation method therefor, prepreg and a composite material. The flame-retardant epoxy resin composition comprises an epoxy resin, a halogen-free flame retardant, and an epoxy resin curing agent; the weight of the epoxy resin accounts for 55-70% of the weight of the flame-retardant epoxy resin composition, the weight of the halogen-free flame retardant accounts for 25-36% of the weight of the flame-retardant epoxy resin composition, the gel time of the flame-retardant epoxy resin composition at 150°C is less than or equal to 150 sec, and the glass transition temperature of the cured flame-retardant epoxy resin composition is greater than or equal to 120°C. The present invention solves the problems of large flame retardant addition proportion, lower curing speed, reduction of the heat resistance Tg of a resin, and significant reduction of the mechanical properties of an epoxy composite material when existing flame-retardant epoxy resin compositions have excellent flame-retardant properties.

Description

Flame retardant epoxy resin composition, preparation method thereof, prepreg and composite material

[0001] Cross-references

[0002] This application claims priority to Chinese application No. 2024102619096, filed on March 7, 2024. The contents of the above application are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of epoxy resins, and in particular to a flame retardant epoxy resin composition and a preparation method thereof, a prepreg and a composite material. Background Art

[0004] Fiber-reinforced composites made with epoxy resin as a matrix boast lightweight and high strength, and are widely used in the manufacturing of aircraft structures, windmill blades, and automobile hulls. The demand for and application of fiber-reinforced composites is increasing year by year. However, while these epoxy resin-based fiber-reinforced composites offer excellent performance, they also suffer from flammability, limiting their potential for expanded applications and posing a potential safety hazard.

[0005] Conventional flame-retardant composite materials often use halogen-containing flame-retardant solutions such as bromine-containing epoxy. Although these materials can impart flame-retardant properties, they produce large amounts of smoke upon combustion, which is highly toxic. This smoke is not conducive to fire escape, causes significant harm to the human body, and pollutes the surrounding environment. Related technologies add halogen-free flame retardants to epoxy resins, using phosphate compounds and phosphazene compounds to reduce smoke production. However, this solution also has some problems. The inventors found that phosphate compounds and phosphazene compounds are prone to migration and hydrolysis, which in turn affects the stability of the flame-retardant properties of the resulting composite material. Secondly, when the amount of phosphate compounds and phosphazene compounds added is large, the glass transition temperature (Tg) of the cured resin is significantly reduced.

[0006] Therefore, there is an urgent need to develop a flame retardant epoxy resin composition and a preparation method thereof, a prepreg and a composite material to solve the above problems.

[0007] Summary of the Invention

[0008] The object of the present invention is to provide a flame-retardant epoxy resin composition and its preparation method, prepreg and composite material, so as to solve the problem that the existing flame-retardant epoxy resin composition has excellent flame retardant properties, but the flame retardant addition ratio is large, the curing speed is slow, the resin heat resistance Tg is reduced, and the mechanical properties of the epoxy composite material are significantly reduced.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a flame retardant epoxy resin composition, comprising an epoxy resin, a halogen-free flame retardant, and an epoxy resin curing agent, wherein the weight of the epoxy resin accounts for 55% to 70% of the weight of the flame retardant epoxy resin composition, and the weight of the halogen-free flame retardant accounts for 25 to 36% of the weight of the flame retardant epoxy resin composition;

[0010] The epoxy resin is selected from one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, and toughened modified epoxy resin;

[0011] The halogen-free flame retardant is selected from at least one of piperazine pyrophosphate, triphenylphosphine oxide, melamine pyrophosphate, melamine cyanurate, ammonium polyphosphate, alkyl hypophosphite, coated red phosphorus, aluminum hydroxide, magnesium hydroxide, and zinc borate;

[0012] The gel time of the flame retardant epoxy resin composition at 150° C. is ≤150 sec, and the glass transition temperature of the flame retardant epoxy resin composition after curing is ≥120° C.

[0013] By using a combination of phosphorus-containing flame retardants and nitrogen-containing flame retardants for synergistic flame retardancy, high-efficiency flame retardancy can be achieved and the proportion of flame retardant addition can be reduced. Phosphorus-containing flame retardants such as piperazine pyrophosphate, melamine pyrophosphate, and ammonium polyphosphate belong to an expansion flame retardant system. The phosphorus element in the flame retardant promotes the dehydration of epoxy to carbon, and forms a phosphorus-rich glassy substance to cover the surface of the material to isolate the air and internal flammable gas production. The nitrogen element in the flame retardant partially releases non-combustible gas for flame retardancy, and at the same time causes the carbon layer formed by the flame retardant to expand and foam to form a porous carbon layer, which isolates the air and internal flammable gas production to achieve good flame retardant performance, thereby making the flame retardant performance of the flame retardant epoxy resin composition reach UL94 V-0; at the same time, by adopting the above technical solution, the tensile strength of the flame retardant epoxy resin composition is not less than 56.75 MPa, and the glass transition temperature after curing is not less than 121°C, so that it is suitable for the liquid molding process of composite materials, has an operating cycle at room temperature and can be quickly cured and molded at medium and high temperatures (the gel time at 150°C does not exceed 150 seconds), and the tensile strength of the obtained composite material is not less than 485 MPa, and can reach up to 550 MPa.

[0014] Optionally, the weight of the epoxy resin accounts for 58%-63% of the weight of the flame retardant epoxy resin composition, and the weight of the halogen-free flame retardant accounts for 31-36% of the weight of the flame retardant epoxy resin composition.

[0015] Optionally, the epoxy equivalent of the epoxy resin is 150-450 g / eq, and the particle size D50 of the halogen-free flame retardant is ≤20 μm.

[0016] Optionally, the weight of the epoxy resin curing agent accounts for 4%-6% of the weight of the flame retardant epoxy resin composition, and the epoxy resin curing agent includes a latent curing agent and an accelerator, and the weight ratio of the latent curing agent to the accelerator is (1-3):1.

[0017] Optionally, the latent curing agent is selected from one or more of aromatic amines, dicyandiamide, organic hydrazides, modified aromatic amines, modified dicyandiamides, modified organic hydrazides, and linear phenolic resins.

[0018] Optionally, the accelerator is at least one of organic urea, modified organic urea, tertiary amine, imidazole, modified imidazole, quaternary ammonium salt and quaternary phosphonium salt.

[0019] Optionally, the halogen-free flame retardant includes the ammonium polyphosphate and the melamine cyanurate, and the weight ratio of the ammonium polyphosphate to the melamine cyanurate is 1:1 to 4:1.

[0020] In a second aspect, the present invention provides a method for preparing a flame-retardant epoxy resin composition, comprising: preheating a mixing device to 100-120°C, sequentially adding an epoxy resin and a halogen-free flame retardant to the mixing device and mixing them evenly, then cooling the temperature to 55-75°C and adding the epoxy resin curing agent to obtain the flame-retardant epoxy resin composition.

[0021] In a third aspect, the present invention provides a prepreg obtained by impregnating reinforcing fibers with the flame retardant epoxy resin composition.

[0022] In a fourth aspect, the present invention provides a composite material obtained by curing the prepreg, wherein the curing pressure is 4-6 MPa and the curing time is 5-15 min.

[0023] The beneficial effects of the present invention include:

[0024] 1. The flame-retardant epoxy resin composition provided by the present invention adopts a compounding technology of multiple halogen-free flame retardants. Under the condition that the content of the halogen-free flame retardant added to the flame-retardant epoxy resin composition is less than 36wt%, the flame-retardant epoxy resin composition has a tensile strength of not less than 56.75MPa and a glass transition temperature after curing of not less than 120°C. The flame retardant performance of the composite material plate reaches UL94 V-0, and the composite material plate also has excellent mechanical properties and heat resistance.

[0025] 2. The flame retardant epoxy resin composition provided by the present invention has good fluidity and has good wettability to the reinforcing fibers when preparing prepregs, and can fully exert the high strength characteristics of the reinforcing fibers.

[0026] 3. The curing agent and accelerator of the specific particle size of the present invention can cooperate with each other, and the obtained resin has a short gel time. The prepared prepreg is suitable for rapid molding, thereby improving the production efficiency of the composite material.

[0027] 4. The flame-retardant epoxy composition of the present invention adopts halogen-free flame retardant compounding technology, and the prepreg prepared has excellent flame retardant properties, and does not produce a large amount of thick smoke and toxic and harmful gases when burned, which is more in line with the development trend of flame retardancy, environmental protection, low smoke and low toxicity. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] The present invention provides a flame retardant epoxy resin composition, comprising an epoxy resin, a halogen-free flame retardant and an epoxy resin curing agent, wherein the weight of the epoxy resin accounts for 55% to 70% of the weight of the flame retardant epoxy resin composition, and the weight of the halogen-free flame retardant accounts for 25 to 36% of the weight of the flame retardant epoxy resin composition;

[0030] The epoxy resin is selected from one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, and toughened modified epoxy resin;

[0031] The halogen-free flame retardant is selected from at least one of piperazine pyrophosphate, triphenylphosphine oxide, melamine pyrophosphate, melamine cyanurate, ammonium polyphosphate, alkyl hypophosphite, coated red phosphorus, aluminum hydroxide, magnesium hydroxide, and zinc borate;

[0032] The gel time of the flame retardant epoxy resin composition at 150° C. is ≤150 sec, and the glass transition temperature of the flame retardant epoxy resin composition after curing is ≥120° C.

[0033] In some embodiments of the present invention, the weight of the epoxy resin accounts for 58%-63% of the weight of the flame retardant epoxy resin composition, the weight of the halogen-free flame retardant accounts for 31-36% of the weight of the flame retardant epoxy resin composition, and the weight of the epoxy resin curing agent accounts for 5.2%-5.9% of the weight of the flame retardant epoxy resin composition.

[0034] In some embodiments of the present invention, the epoxy equivalent of the epoxy resin is 150-450 g / eq.

[0035] In some embodiments of the present invention, the epoxy resin accounts for 50-70% of the total mass of the raw materials.

[0036] In some embodiments of the present invention, the epoxy resin is selected from one or more of NPEL-128, NPEF-170, NPES-901, NPPN-638S, DER 858, and MY-720.

[0037] In some embodiments of the present invention, NPEL-128 is purchased from Nanya Electronic Materials (Kunshan) Co., Ltd., a low-viscosity liquid bisphenol A epoxy resin, epoxy equivalent weight: EEW = 184-190 g / eq., viscosity at 25°C: 12000-15000 mPa.s.

[0038] In some specific embodiments of the present invention, NPEF-170 is purchased from Nan Ya Plastics Industrial Co., Ltd., and is a low-viscosity liquid bisphenol F epoxy resin with an epoxy equivalent weight (EEW) of 160-180 g / eq. and a viscosity at 25° C. of 2000-5000 mPa.s.

[0039] In some specific embodiments of the present invention, NPES-901 is purchased from Nanya Electronic Materials (Kunshan) Co., Ltd., and is a solid bisphenol A epoxy resin with an epoxy equivalent weight (EEW) of 450 to 500 g / eq. and a softening point of 67 to 74°C.

[0040] In some embodiments of the present invention, NPPN-638S is purchased from Nan Ya Plastics Industrial Co., Ltd., and is a linear phenolic epoxy resin with an epoxy equivalent weight (EEW) of 184-190 g / eq. and a viscosity of 12,000-15,000 mPa.s at 70°C.

[0041] In some specific embodiments of the present invention, DER 858, purchased from Olin Company, is a polyurethane-modified toughened epoxy resin with an epoxy equivalent weight (EEW) of 380-420 g / eq. and a softening point of 95-105°C.

[0042] In some embodiments of the present invention, MY-720 resin is purchased from Huntsman Corporation, and is a glycidylamine-type tetrafunctional epoxy resin with an epoxy equivalent weight (EEW) of 105 to 118 g / eq. and a viscosity at 50° C. of 3000 to 7000 mPa.s.

[0043] In some embodiments of the present invention, the particle size D50 of the halogen-free flame retardant is ≤20 μm.

[0044] In some embodiments of the present invention, the halogen-free flame retardant is selected from at least one of piperazine pyrophosphate, triphenylphosphine oxide, melamine pyrophosphate, melamine cyanurate, ammonium polyphosphate, alkyl hypophosphite, coated red phosphorus, aluminum hydroxide, magnesium hydroxide, and zinc borate.

[0045] In some embodiments of the present invention, the piperazine pyrophosphate (PAPP) has a D50 of ≤10 μm and is manufactured by Guangzhou Edenda Chemical Co., Ltd. under the trade name NH-5000C.

[0046] In some embodiments of the present invention, the triphenylphosphine oxide (TOA) has a phosphorus content of 11.1 wt %, and is purchased from Guangzhou Xijia New Materials Co., Ltd.

[0047] In some embodiments of the present invention, the melamine pyrophosphate (MPP) D50≤10 μm is purchased from Dongguan Hongtaiji Flame Retardant Materials Co., Ltd.

[0048] In some embodiments of the present invention, the melamine cyanurate (MCA) D50≤5 μm is purchased from Dongguan Hongtaiji Flame Retardant Materials Co., Ltd. MC-151.

[0049] In some embodiments of the present invention, the degree of polymerization of ammonium polyphosphate (APP) is greater than 1000, the particle size D50 is less than or equal to 20 μm, and the brand is Clariant AP-428.

[0050] In some embodiments of the present invention, the ammonium polyphosphate is epoxy-coated ammonium polyphosphate or melamine-coated ammonium polyphosphate. The melamine-coated ammonium polyphosphate has a degree of polymerization ≥ 2000 and a particle size D50 of 5-10 μm. The product is manufactured by Guangzhou Edenda Chemical Co., Ltd. under the trade name NH-3001A. The melamine-coated ammonium polyphosphate has a phosphorus content ≥ 28% and a nitrogen content ≥ 17.5%.

[0051] In some embodiments of the present invention, the epoxy-coated ammonium polyphosphate has a degree of polymerization greater than 1000 and a particle size D50 ≤ 18 μm, and is manufactured by Shenzhen Huayan Flame Retardant New Materials Co., Ltd. The epoxy-coated ammonium polyphosphate has a phosphorus content of ≥ 28% and a nitrogen content of ≥ 14%.

[0052] In some embodiments of the present invention, the alkyl hypophosphite is diethyl aluminum hypophosphite (ADP), with a particle size D50 ≤ 5 μm, from Jiangsu Liside New Materials Co., Ltd.

[0053] In some embodiments of the present invention, the coated red phosphorus is sourced from MCP85-1000 and MCP80-1000 from Anhui Ma'anshan High-Tech Chemical Factory, or from the coated red phosphorus flame retardant from Shanghai Xusen Non-Halogen Smoke Suppression Flame Retardant Co., Ltd., or from Tu-1 from the Shanxi Chemical Research Institute. MCP85-1000 has a phosphorus content of 83% to 85%, while MCP80-1000 has a phosphorus content of 78% to 83%. Tu-1 is a non-halogen composite flame retardant with red phosphorus as its core, compounded with other synergistic flame retardants.

[0054] In some embodiments of the present invention, the aluminum hydroxide (ATH) has a particle size D50 ≤ 8 μm and is purchased from Dongguan Hongtaiji Flame Retardant Materials Co., Ltd.

[0055] In some embodiments of the present invention, the zinc borate is hydrated zinc borate with a particle size D50≤10 μm, purchased from Hefei Wanran New Material Technology Co., Ltd.

[0056] In some embodiments of the present invention, the halogen-free flame retardant further comprises resorcinol bis(diphenyl phosphate) (RDP), which is sourced from Tokyo Chemical Industry (Shanghai) Co., Ltd.

[0057] In some embodiments of the present invention, the weight of the epoxy resin curing agent accounts for 4%-6% of the weight of the flame retardant epoxy resin composition, and the epoxy resin curing agent includes a latent curing agent and an accelerator, and the weight ratio of the latent curing agent to the accelerator is (1-3):1.

[0058] In some embodiments of the present invention, the latent curing agent is selected from one or more of aromatic amines, dicyandiamide, organic hydrazides, modified aromatic amines, modified dicyandiamides, modified organic hydrazides, and linear phenolic resins.

[0059] In some embodiments of the present invention, the accelerator is at least one of organic urea, modified organic urea, tertiary amine, imidazole, modified imidazole, quaternary ammonium salt and quaternary phosphonium salt.

[0060] In some embodiments of the present invention, the latent curing agent is Dyhard 100S produced by Aziken Chemicals, with a melting point of 209-212° C. and a D90 particle size of 1-10 μm.

[0061] In some embodiments of the present invention, the accelerator is UR500 produced by Azken Chemicals and / or diethyltetramethylimidazole (2E4MZ) produced by Siguo Chemicals and / or tetrabutylammonium bromide (TBAB) produced by Kent Catalyst.

[0062] In some embodiments of the present invention, the halogen-free flame retardant includes the ammonium polyphosphate and the melamine cyanurate, and the weight ratio of the ammonium polyphosphate to the melamine cyanurate is 1:1 to 4:1.

[0063] In some embodiments of the present invention, the flame retardant epoxy resin composition further comprises an auxiliary agent, and the weight of the auxiliary agent accounts for 0.5 to 1% of the weight of the flame retardant epoxy resin composition.

[0064] The present invention does not specify the auxiliary agent, and the experimenter can select it according to the needs, for example: wetting agent, dispersant, defoaming agent, etc. In some embodiments, the auxiliary agent is selected from BYK-W980 and BYK-A530.

[0065] It is worth noting that the present invention also provides a method for preparing a flame-retardant epoxy resin composition, comprising: preheating a mixing device to 100-120°C, sequentially adding an epoxy resin and a halogen-free flame retardant to the mixing device and mixing them uniformly, then cooling the mixture to 55-75°C and adding the epoxy resin curing agent to obtain the flame-retardant epoxy resin composition. Alternatively, the method for preparing a flame-retardant epoxy resin composition comprises: preheating a mixing device to 100-120°C, sequentially adding an epoxy resin, an additive, and a halogen-free flame retardant to the mixing device and mixing them uniformly, then cooling the mixture to 55-75°C and adding the epoxy resin curing agent to obtain the flame-retardant epoxy resin composition.

[0066] The present invention also provides a prepreg obtained by impregnating reinforcing fibers with the flame-retardant epoxy resin composition. The prepreg comprises the following steps: applying the flame-retardant epoxy resin composition to reinforcing fibers using a hot-melt prepreg coating machine to form a resin film; then, using a hot-melt prepreg impregnation machine, composite-impregnating the resin film with the reinforcing fibers to obtain the prepreg. The prepreg has a resin content of 35-45%.

[0067] The reinforcing fibers used in the examples of the present invention are all glass fibers, but the reinforcing fibers that can be used in the prepreg include, but are not limited to, glass fibers, carbon fibers, aramid fibers, and basalt fibers.

[0068] It is worth noting that the present invention also provides a composite material obtained by curing the prepreg, wherein the curing pressure is 4-6 MPa and the curing time is 5-15 minutes. Specifically, the composite material comprises the following steps: preheating a mold device to 140-16°C, spraying a release agent in the cavity of the mold device, and then placing the prepreg in the cavity of the mold device and curing it to obtain the composite material, wherein the curing pressure is 4-6 MPa and the curing time is 5-15 minutes.

[0069] In one embodiment, the method for preparing the fiber-reinforced composite material comprises: curing a prepreg or a prepreg and a flame-retardant epoxy resin composition.

[0070] Examples 1-6

[0071] The flame-retardant epoxy resin composition is prepared as follows: preheating a mixing device to 110° C., sequentially adding the epoxy resin and additives listed in Table 1 to the mixing device according to the quantities listed in Table 1 and mixing them uniformly, then adding the halogen-free flame retardant listed in Table 1 and mixing them uniformly to obtain a mixture, cooling the mixture to 65° C., then adding the epoxy resin curing agent listed in Table 1 and mixing them uniformly to obtain a flame-retardant epoxy resin composition. The quantities of the components in Table 1 are calculated in parts by weight.

[0072] Table 1 Note: “ / ” in the table means none.

[0073] The flame retardant epoxy resin compositions obtained in Examples 1-6 were subjected to vacuum degassing and casting of resin tensile and impact test strips according to GB / T2567-2008 standard, and the curing condition was 140° C. for 2 hours to obtain cured epoxy resin castings.

[0074] The flame retardant epoxy resin compositions of Examples 1-6 were tested as follows:

[0075] (1) Viscosity: The viscosity of the flame retardant epoxy resin composition at 70°C was tested using a DHR-20 dynamic shear rheometer (TA, USA);

[0076] (2) Gel time: The gel time of the flame retardant epoxy resin composition at 150°C was tested using a gel time tester;

[0077] (3) Glass transition temperature (Tg): The Tg of the flame retardant epoxy resin composition cured casting was measured using a differential scanning calorimeter X3 DSC (TA, USA) in accordance with the standard GB / T 19466-2004;

[0078] (4) Mechanical properties: The tensile strength, tensile modulus, and elongation at break of the flame retardant epoxy resin composition cured casting were determined using an electronic universal tensile testing machine based on ISO 527-2. The simply supported beam impact strength of the flame retardant epoxy resin composition cured casting was determined using a simply supported beam impact testing machine based on GBT 1043.1.

[0079] The test results of Examples 1-6 are shown in Table 2.

[0080] Table 2 Note: The weight ratio of the halogen-free flame retardant refers to the percentage of the weight of the halogen-free flame retardant to the total weight of the flame retardant epoxy resin composition.

[0081] As shown in Table 2, when the weight ratio of the halogen-free flame retardant is less than 36%, the gel time of the flame retardant epoxy resin composition at 150°C is less than 150 seconds, and it has rapid curing and molding characteristics; the glass transition temperature (Tg) of the flame retardant epoxy resin composition is not less than 121°C, and the flame retardant epoxy resin composition has good heat resistance; and the flame retardant epoxy resin composition has the following advantages: viscosity at 70°C is greater than 14100mPa.s, tensile strength is greater than 58Mpa, tensile modulus is greater than 4.1Gpa, elongation at break is greater than 2%, and impact strength is greater than 11KJ / m 2 .

[0082] Examples 7-13

[0083] The flame-retardant epoxy resin composition is prepared as follows: preheating a mixing device to 110°C, sequentially adding the epoxy resin and additives listed in Table 3 to the mixing device according to the quantities listed in Table 3 and mixing them uniformly, then adding the halogen-free flame retardant listed in Table 3 and mixing them uniformly to obtain a mixture, cooling the mixture to 65°C, then adding the epoxy resin curing agent listed in Table 3 and mixing them uniformly to obtain a flame-retardant epoxy resin composition. The quantities of the components in Table 3 are calculated in parts by weight.

[0084] Table 3 Note: “ / ” means none.

[0085] The flame retardant epoxy resin compositions obtained in Examples 7 to 13 were respectively used to prepare epoxy resin composition cured castings in the same manner as in Examples 1 to 6.

[0086] The viscosity and gel time of the flame retardant epoxy resin compositions of Examples 7-13 were tested, and the Tg and mechanical properties of the cured epoxy resin castings obtained in Examples 7-13 were tested using the same testing methods as in Examples 1-6. The test results are shown in Table 4.

[0087] Table 4 Note: The weight ratio of the halogen-free flame retardant refers to the percentage of the weight of the halogen-free flame retardant to the total weight of the flame retardant epoxy resin composition.

[0088] It can be seen from Table 4 that when the weight ratio of the halogen-free flame retardant is less than 36%, the gel time of the flame retardant epoxy resin at 150°C is less than 110 seconds, and it has rapid curing and molding characteristics; the glass transition temperature (Tg) of the flame retardant epoxy resin composition is not less than 121°C, and the flame retardant epoxy resin composition has good heat resistance; and the flame retardant epoxy resin composition has the following advantages: viscosity at 70°C is greater than 12600mPa.s, tensile strength is greater than 56Mpa, tensile modulus is greater than 4.1Gpa, elongation at break is greater than 2%, and impact strength is greater than 10KJ / m 2 .

[0089] Preparation of prepreg (flame retardant glass cloth prepreg):

[0090] The flame retardant epoxy resin compositions obtained in Examples 7 to 13 were applied to glass cloth using a hot melt prepreg coating machine to form resin films. The surface density of the resin films was 135 g / m 2 The glass cloth is Chongqing International E-Glass glass cloth fabric EWR400, with a checkered plain weave and a surface density of 400g / m2 ; Then a hot melt prepreg impregnation machine was used to composite the two layers of resin film with EWR400 glass cloth fabric and impregnate them to prepare the corresponding prepregs (flame retardant glass cloth prepregs) of the flame retardant epoxy resin compositions of Examples 7 to 13, respectively. The resin content of the prepregs (flame retardant glass cloth prepregs) was 40.3%.

[0091] Preparation of composite materials (flame retardant glass cloth prepreg sheets):

[0092] A flat-plate molding die with a mold cavity thickness of 2.1 mm was preheated to 150°C, and then a release agent was evenly sprayed on it; 7 pieces of the prepared flame-retardant glass cloth prepreg were cut, and the 7 pieces of flame-retardant glass cloth prepreg were stacked according to a 0° / 0° / 0° / 0° / 0° / 0° / 0° stacking structure, where 0° was along the warp direction of the flame-retardant glass cloth prepreg and 90° was along the weft direction of the flame-retardant glass cloth prepreg. The preheated flat-plate molding die was then pressurized to a maximum pressure of 5.0 MPa according to a procedure, and the pressure was maintained and hot pressed for 10 minutes. After the hot pressing was completed, a composite material sheet with a thickness of 2.1 mm (i.e., a flame-retardant glass cloth composite material sheet) was obtained.

[0093] Based on the GBT 1447-2005 standard, six dumbbell-shaped tensile test pieces with a length of 180 mm and a test section width of 10 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The tensile strength, tensile modulus, and elongation at break of the dumbbell-shaped tensile test pieces (i.e., the fiber-reinforced composite sheet) were tested. The test results are shown in Table 5.

[0094] Based on the GB / T1450.1-2005 standard, 10 short beam shear test specimens with a length of 21 mm and a width of 10.5 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The interlaminar shear strength of the short beam shear test specimens (i.e., the fiber-reinforced composite sheet) was tested. The test results are shown in Table 5.

[0095] Based on the UL94-2013 vertical combustion standard, 20 vertical combustion test pieces with a length of 130 mm and a width of 13 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The vertical combustion flame retardant properties of the vertical combustion test pieces (i.e., fiber-reinforced composite sheet) were tested. The test results are shown in Table 5.

[0096] Table 5 Note: The flame retardant properties of the panels in the table refer to the flame retardant properties of fiber reinforced composite panels with a thickness of 2.1 mm.

[0097] The data in Table 5 show that, by using a halogen-free flame retardant compounded with a flame-retardant epoxy solution, the flame-retardant epoxy resin composition has a gel time of less than 150 seconds at 150°C, has rapid curing and molding characteristics, and has good mechanical properties after curing, a glass transition temperature Tg of not less than 120°C, and has good heat resistance. The fiber-reinforced composite material sheet prepared from the flame-retardant epoxy resin composition has excellent tensile properties and interlaminar shear strength, and excellent flame retardant properties. The vertical combustion test of the fiber-reinforced composite material sheet with a thickness of 2.1 mm reaches the UL94 V-0 grade.

[0098] Comparative Examples 1-6

[0099] The flame-retardant epoxy resin composition is prepared as follows: preheat a mixing device to 110°C, sequentially add the epoxy resin and additives listed in Table 6 to the mixing device according to the quantities listed in Table 6 and mix uniformly, then add the halogen-free flame retardant listed in Table 6 and mix uniformly to obtain a mixture, cool the mixture to 65°C, then add the epoxy resin curing agent listed in Table 6 and mix uniformly to obtain a flame-retardant epoxy resin composition. The quantities of the components in Table 6 are in parts by weight.

[0100] Table 6 Note: “ / ” means none.

[0101] The flame retardant epoxy resin compositions obtained in Comparative Examples 1-6 were respectively used to prepare epoxy resin composition cured castings in the same manner as in Examples 1-6.

[0102] The flame retardant epoxy resin compositions of Comparative Examples 1-6 were tested for viscosity and gel time, and the cured cast epoxy resin compositions obtained in Comparative Examples 1-6 were tested for Tg and mechanical properties. The testing methods were the same as those in Examples 1-6. The test results are shown in Table 7.

[0103] The flame retardant epoxy resin compositions obtained in Comparative Examples 1-6 were respectively applied on glass cloth using a hot melt prepreg coating machine to prepare resin films. The surface density of the resin films was 135 g / m 2 The glass cloth is Chongqing International E-Glass glass cloth fabric EWR400, with a checkered plain weave and a surface density of 400g / m 2 Then, a hot melt prepreg impregnation machine was used to impregnate the two layers of resin film with EWR400 glass cloth fabric to prepare the corresponding prepregs (flame retardant glass cloth prepregs) of the flame retardant epoxy resin compositions of Comparative Examples 1-6, respectively. The resin content of the prepregs (flame retardant glass cloth prepregs) was 40.3%.

[0104] Preparation of composite materials (flame retardant glass cloth prepreg sheets):

[0105] A flat-plate molding die with a mold cavity thickness of 2.1 mm was preheated to 150°C, and then a release agent was evenly sprayed on it; 7 pieces of the prepared flame-retardant glass cloth prepreg were cut, and the 7 pieces of flame-retardant glass cloth prepreg were stacked according to a 0° / 0° / 0° / 0° / 0° / 0° / 0° stacking structure, where 0° was along the warp direction of the flame-retardant glass cloth prepreg and 90° was along the weft direction of the flame-retardant glass cloth prepreg. The preheated flat-plate molding die was then pressurized to a maximum pressure of 5.0 MPa according to a procedure, and the pressure was maintained and hot pressed for 10 minutes. After the hot pressing was completed, a composite material sheet with a thickness of 2.1 mm (i.e., a flame-retardant glass cloth composite material sheet) was obtained.

[0106] Based on the GBT 1447-2005 standard, six dumbbell-shaped tensile test pieces with a length of 180 mm and a test section width of 10 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The tensile strength, tensile modulus, and elongation at break of the dumbbell-shaped tensile test pieces (i.e., the fiber-reinforced composite sheet) were tested. The test results are shown in Table 7.

[0107] Based on the GB / T1450.1-2005 standard, 10 short beam shear test specimens with a length of 21 mm and a width of 10.5 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The interlaminar shear strength of the short beam shear test specimens (i.e., the fiber-reinforced composite sheet) was tested. The test results are shown in Table 7.

[0108] Based on the UL94-2013 vertical combustion standard, 20 vertical combustion test pieces with a length of 130 mm and a width of 13 mm were prepared along the 0° direction (i.e., the radial direction of the fiber-reinforced composite sheet) of the composite sheet. The vertical combustion flame retardant properties of the vertical combustion test pieces (i.e., fiber-reinforced composite sheet) were tested. The test results are shown in Table 7.

[0109] Table 7 Note: “ / ” in the table means none; the flame retardant performance of the board refers to the flame retardant performance of the fiber reinforced composite board with a thickness of 2.1mm.

[0110] As shown in Table 7, the flame retardant epoxy resin composition obtained in Comparative Example 1 adopts the ammonium polyphosphate flame retardant solution, and has slightly poor flame retardant performance. The vertical burning performance of the prepared fiber reinforced composite material plate is UL94 V-1 grade.

[0111] The flame-retardant epoxy resin composition obtained in Comparative Example 2 adopts a flame-retardant solution of ammonium polyphosphate (AP-428) and zinc borate. Although the vertical combustion performance of the prepared fiber-reinforced composite material plate reaches the UL94 V-0 grade, the addition amount of the halogen-free flame retardant exceeds 36%, resulting in a decrease in the mechanical properties of the flame-retardant epoxy resin composition after curing, and the performance of the prepared fiber-reinforced composite material plate is also significantly reduced.

[0112] The flame retardant epoxy resin composition obtained in Comparative Example 3 adopts a flame retardant scheme of aluminum hydroxide (ATH) and ammonium polyphosphate (AP-428), but the addition amount of the halogen-free flame retardant exceeds 36%, but the flame retardant performance is low, and the vertical burning performance of the fiber-reinforced composite material plate is UL94 V-1 grade.

[0113] The flame retardant epoxy resin composition obtained in Comparative Example 4 adopts a flame retardant scheme of zinc borate, aluminum hydroxide (ATH) and melamine urate (MC-151), but the addition amount of the halogen-free flame retardant exceeds 36%. However, the flame retardant performance is low, and the vertical burning performance of the fiber-reinforced composite material plate is UL94 V-1 grade.

[0114] The flame retardant epoxy resin composition obtained in Comparative Example 5 adopts a flame retardant scheme of aluminum hydroxide (ATH) and triphenylphosphine oxide (TOA), but the addition amount of the halogen-free flame retardant exceeds 40%, resulting in a decrease in the mechanical properties of the flame retardant epoxy resin composition after curing. The performance of the prepared fiber-reinforced composite material plate is significantly reduced, and the flame retardant performance is slightly poor. The vertical burning performance of the fiber-reinforced composite material plate is UL94 V-1 grade.

[0115] The flame retardant epoxy resin composition obtained in Comparative Example 6 adopts a flame retardant scheme of resorcinol bis(diphenyl phosphate) (RDP), ammonium polyphosphate (AP-428) and aluminum hydroxide (ATH). Although the vertical burning performance of the prepared fiber-reinforced composite material plate reaches the UL94 V-0 grade, the gel time of the flame retardant epoxy resin composition at 150°C is extended by more than 200 seconds after the addition of the phosphate flame retardant, the curing speed is slow, and the glass transition temperature of the flame retardant epoxy resin composition after curing is 102°C, which is reduced by 20°C. The heat resistance of the flame retardant epoxy resin composition is reduced, and the performance of the prepared fiber-reinforced composite material plate is also significantly reduced.

[0116] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A flame retardant epoxy resin composition, characterized in that The flame retardant epoxy resin composition comprises an epoxy resin, a halogen-free flame retardant and an epoxy resin curing agent, wherein the weight of the epoxy resin accounts for 55% to 70% of the weight of the flame retardant epoxy resin composition, and the weight of the halogen-free flame retardant accounts for 25 to 36% of the weight of the flame retardant epoxy resin composition; The epoxy resin is selected from one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, and toughened modified epoxy resin; The halogen-free flame retardant is selected from at least one of piperazine pyrophosphate, triphenylphosphine oxide, melamine pyrophosphate, melamine cyanurate, ammonium polyphosphate, alkyl hypophosphite, coated red phosphorus, aluminum hydroxide, magnesium hydroxide, and zinc borate; The gel time of the flame retardant epoxy resin composition at 150° C. is ≤150 sec, and the glass transition temperature of the flame retardant epoxy resin composition after curing is ≥120° C.

2. The flame retardant epoxy resin composition according to claim 1, characterized in that The weight of the epoxy resin accounts for 58% to 63% of the weight of the flame retardant epoxy resin composition, and the weight of the halogen-free flame retardant accounts for 31 to 36% of the weight of the flame retardant epoxy resin composition.

3. The flame retardant epoxy resin composition according to claim 1, characterized in that The epoxy equivalent of the epoxy resin is 150-450 g / eq, and the particle size D50 of the halogen-free flame retardant is ≤20 μm.

4. The flame retardant epoxy resin composition according to claim 1, characterized in that The weight of the epoxy resin curing agent accounts for 4%-6% of the weight of the flame retardant epoxy resin composition. The epoxy resin curing agent includes a latent curing agent and an accelerator. The weight ratio of the latent curing agent to the accelerator is (1-3):

1.

5. The flame retardant epoxy resin composition according to claim 4, characterized in that The latent curing agent is selected from one or more of aromatic amines, dicyandiamide, organic hydrazides, modified aromatic amines, modified dicyandiamides, modified organic hydrazides, and linear phenolic resins.

6. The flame retardant epoxy resin composition according to claim 4, characterized in that The accelerator is at least one of organic urea, modified organic urea, tertiary amine, imidazole, modified imidazole, quaternary ammonium salt and quaternary phosphonium salt.

7. The flame retardant epoxy resin composition according to claim 1, characterized in that The halogen-free flame retardant includes the ammonium polyphosphate and the melamine cyanurate, and the weight ratio of the ammonium polyphosphate to the melamine cyanurate is 1:1 to 4:

1.

8. A method for preparing a flame retardant epoxy resin composition, characterized in that: include: After preheating the mixing device to 100-120° C., the epoxy resin and halogen-free flame retardant according to any one of claims 1 to 7 are sequentially added to the mixing device and mixed evenly, and then the epoxy resin curing agent is added after cooling to 55-75° C. to obtain the flame-retardant epoxy resin composition.

9. A prepreg, characterized in that The flame retardant epoxy resin composition is obtained by impregnating reinforcing fibers with the flame retardant epoxy resin composition according to any one of claims 1 to 7.

10. A fiber-reinforced composite material, characterized in that: The prepreg according to claim 9 is obtained by curing the prepreg, wherein the curing pressure is 4-6 MPa and the curing time is 5-15 min.