Flame-retardant ethylene propylene diene monomer material and preparation method thereof

Abstract

The invention relates to a flame-retardant ethylene propylene diene monomer material and a preparation method thereof, and relates to the technical field of flame-retardant rubber materials. The flame-retardant ethylene propylene diene monomer material comprises 55-75 parts of ethylene propylene diene monomer, 20-30 parts of a flame retardant, 5-15 parts of aluminum hydroxide, 2-3 parts of a vulcanizing agent, 2-6 parts of a carbon layer reinforcing agent, 1-3 parts of a catalytic synergist, 2-4 parts of an accelerant and 2-4 parts of a processing aid. The flame-retardant ethylene propylene diene monomer material has the characteristics of excellent flame retardance, mechanical property and environment friendliness through the synergistic effect of the components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame-retardant rubber materials, in particular to a flame-retardant EPDM rubber material and a preparation method thereof. BACKGROUND

[0002] At present, EPDM rubber is widely used in the fields of wire and cable insulation layer, building sealing strip, automobile parts, etc. due to its special saturated main chain and a small amount of unsaturated side chain molecular structure, which has good weather resistance, electrical insulation, chemical stability, high softness and high elasticity. However, EPDM rubber itself belongs to non-polar and high carbon and hydrogen content rubber, which is easy to burn, and the oxygen index is usually about 18%, which is easy to burn in air and releases a large amount of heat and smoke, limiting the application range of EPDM rubber.

[0003] The Chinese invention patent with publication number CN10459264A discloses a flame-retardant EPDM rubber for cables and a preparation method thereof. The flame-retardant EPDM rubber for cables provided by the invention has excellent flame retardance through the synergistic effect of EPDM rubber, aluminum hydroxide, fumed white carbon black, chlorinated paraffin, hexabromocyclododecane, boehmite, vulcanizing agent and sodium molybdate.

[0004] However, a large amount of aluminum hydroxide needs to be added to the above-mentioned EPDM rubber to achieve the flame-retardant effect, which will significantly deteriorate the mechanical properties, elasticity, processing fluidity, etc. of the EPDM rubber. The Chinese invention patent with publication number CN107857945A discloses an environmentally friendly flame-retardant EPDM rubber damping material, which comprises: EPDM rubber, carbon black, red phosphorus flame retardant RL-EP, modified magnesium hydroxide powder, aluminum hydroxide, white carbon black, naphthenic oil, antioxidant RD, zinc oxide, zinc stearate, active agent PEG-4000, magnesium oxide, release agent L-24, release agent KL-3Q, vulcanizing agent S-80, accelerator. Through the compounding of red phosphorus with magnesium hydroxide and aluminum hydroxide, the synergistic flame-retardant and synergistic reinforcing effects are achieved.

[0005] Although the red phosphorus flame retardant has the advantages of good flame retardance and small amount, the amount of smoke is still large when the material containing the red phosphorus flame retardant burns, and the toxicity is also much smaller than that of halogen flame retardants. Red phosphorus can slowly react with air in a humid environment to produce highly toxic phosphine (PH3) gas, and red phosphorus dust is easy to explode, and a large amount of storage will cause internal high heat and spontaneous combustion, which may cause safety accidents. In addition, the inherent purple color of red phosphorus greatly limits its application, and the flame-retardant material containing red phosphorus releases a large amount of irritating gas during production and combustion. Therefore, it is urgent to develop an EPDM rubber material with both environmental protection and flame retardance. SUMMARY

[0006] To solve the above technical problems, the present application provides a preparation method of a flame-retardant EPDM material. The flame-retardant EPDM material of the present application has excellent flame-retardant performance, mechanical properties and environmental protection characteristics through the synergistic effect between components.

[0007] In a first aspect, the present application provides a flame-retardant EPDM material, which comprises 55-75 parts by weight of EPDM, 20-30 parts by weight of a flame retardant, 5-15 parts by weight of aluminum hydroxide, 2-3 parts by weight of a vulcanizing agent, 2-6 parts by weight of a carbon layer enhancer, 1-3 parts by weight of a catalytic synergist, 2-4 parts by weight of an accelerator, and 2-4 parts by weight of a processing aid.

[0008] Optionally, the flame retardant comprises any one or more of HT-802 aluminum hypophosphite, melamine cyanurate, dioctyl phthalate, and piperazine pyrophosphate.

[0009] In the above technical solution, HT-802 aluminum hypophosphite can decompose to generate phosphoric acid substances at about 200℃, catalyze the dehydration of polymers to form carbon, and release PH3 in the gas phase to capture free radicals.

[0010] Melamine cyanurate can produce non-combustible gases such as NH3 through endothermic decomposition, dilute oxygen, and promote the formation of an expanded carbon layer.

[0011] Piperazine pyrophosphate can decompose to generate ammonia and water vapor at high temperatures (>300℃), and play a role in gas-phase flame retardation and carbon expansion.

[0012] Dioctyl phthalate has both plasticizing and flame-retardant auxiliary functions, improves processing fluidity, and participates in carbon formation during combustion.

[0013] Multiple phosphorus-nitrogen flame retardants are compounded to cover different temperature stages and achieve multiple flame-retardant mechanisms.

[0014] Optionally, the carbon layer enhancer is any one of expandable graphite, silicone resin, and polysiloxane.

[0015] In the above technical solution, the carbon layer enhancer can physically enhance the carbon layer structure and improve the heat and oxygen insulation performance. Expandable graphite expands to form a carbon layer upon heating, physically isolating heat and combustible gases, and interweaving with the chemical carbon layer to enhance it. Silicone resin and polysiloxane form a SiO2 ceramic layer on the surface of the carbon layer during combustion, improving the carbon layer's oxidation resistance and heat insulation. This can form a ceramic-carbon composite barrier with Al2O3 generated by the decomposition of aluminum hydroxide and the phosphorus-based carbon layer.

[0016] Optionally, the catalytic synergist is any one of zinc molybdate, zinc borate, and organic montmorillonite.

[0017] In the technical scheme, the catalytic synergistic agent can catalyze charring, smoke suppression and promote the flame-retardant reaction. Zinc molybdate and zinc borate can catalyze polymer dehydrogenation and cyclization, promote early charring and good charring, and inhibit the generation of smoke in the gas phase. The nano lamella of organic montmorillonite forms a brick structure in the carbon layer, which can prolong the gas diffusion path and enhance the barrier effect.

[0018] Optionally, the aluminum hydroxide is aluminum hydroxide modified by a silane coupling agent, and the treatment step comprises: hydrolyzing the silane coupling agent in an acidic alcohol aqueous solution, then performing high-speed stirring reaction of the silane coupling agent and dry aluminum hydroxide powder at 80-110 DEG C for 30-60 min, the mass of the silane coupling agent is 1.0-3.0% of the mass of the aluminum hydroxide, and then drying and crushing to obtain the modified aluminum hydroxide.

[0019] In the technical scheme, the aluminum hydroxide starts to decompose into Al2O3 and H2O at about 200 DEG C, absorbs a large amount of heat, reduces the surface temperature of the material, dilutes the combustible gas and inhibits combustion. In addition, the aluminum hydroxide can combine with the carbon layer to enhance the thermal stability and mechanical strength of the carbon layer.

[0020] The silane coupling agent can be any one of vinyl silane, amino silane or sulfur-containing silane, but the application is not limited thereto, and other silane coupling agents can also be selected.

[0021] The modified aluminum hydroxide is grafted with the silane coupling agent, which improves the dispersibility and interfacial bonding force of the aluminum hydroxide in the rubber and enhances the synergism with the phosphorus-based flame retardant.

[0022] Optionally, the vulcanizing agent is sulfur, the accelerator is accelerator CZ, and the processing aid is a compound of stearic acid and zinc oxide with a mass ratio of 1:3-5.

[0023] In the technical scheme, sulfur can also act as a crosslinking agent to form a three-dimensional network structure through sulfur bonds, so as to endow the material with elasticity, strength and permanent shape. The moderate crosslinking density is conducive to the formation of a more complete carbon layer.

[0024] The accelerator can accelerate the vulcanization reaction, reduce the vulcanization temperature and time, and improve the crosslinking efficiency. In addition, the accelerator can also make the flame retardant more stable and the carbon layer more complete.

[0025] The stearic acid can act as a lubricant to improve the mixing processability and filler dispersibility. The zinc oxide is activated to promote vulcanization.

[0026] The zinc oxide acts as a vulcanization activator to improve the density and stability of the crosslinking bond. In addition, the zinc oxide also has a certain smoke suppression and auxiliary flame-retardant effect.

[0027] In a second aspect, the application provides a preparation method of the flame-retardant EPDM material. Raw rubber plasticizing: placing the ethylene-propylene-diene rubber on a rubber precision mill, and opening the ethylene-propylene-diene rubber from high to low by adjusting the distance until it is smooth; Mixing of functional fillers: adjusting the roll gap to 2-3 mm, keeping the rubber on the roll to form a uniform stack, under slow stirring, adding the processing aid, aluminum hydroxide, flame retardant, carbon layer enhancer, and catalytic synergist in sequence, slowly and in batches, left and right cutter, triangular bag, mixing for 15-20 min; Thin pass refining and homogenization: gradually reducing the roll gap to 0.5-1.0 mm, and passing the rubber 3-5 times, then widening the roll gap to form a smooth sheet, and taking out the sheet to obtain the masterbatch, and cooling to room temperature and standing for 4-6 h; Mixing of remaining fillers: re-refining the masterbatch on the mill, adding vulcanizing agent and accelerator after the roll is smooth, and quickly mixing uniformly in 3-5 min using small feeding, left and right cutter, and triangular bag, and quickly taking out the sheet to obtain the finished rubber; Hot press vulcanization molding: cutting the finished rubber into the required mass and shape, filling into a mold preheated to 170-180°C, placing on a flat vulcanization machine, and vulcanizing under a pressure of 15-20 MPa for 10-20 min, and quickly cooling after demolding to obtain the flame-retardant ethylene-propylene-diene rubber material.

[0028] In the above technical solution, the smooth rubber in the raw rubber plasticizing step can more effectively wrap and infiltrate the large amount of powder fillers subsequently added, which is the basis for obtaining a uniform blend.

[0029] In the mixing step of functional fillers, the processing aid is added first to form a lubricating layer and an activation layer on the surface of the fillers, promoting the dispersion of subsequent fillers. Aluminum hydroxide, due to its surface organicization, preferentially binds with the rubber matrix to establish a good initial interface. The subsequently added flame retardant, carbon layer enhancer, and catalytic synergist are forced to disperse and embed in the matrix composed of rubber and aluminum hydroxide under strong mechanical shear force. In this process, the functional particles begin to physically contact closely, laying the foundation for the spatial distribution of subsequent chemical synergistic reactions.

[0030] In the thin pass refining and homogenization step, the thin pass process generates extremely high local shear force, which can effectively break up the secondary agglomerates of fillers and achieve uniform dispersion. The standing process allows the internal stress of the rubber molecular chain generated during mixing to relax, and also allows a small amount of unreacted crosslinking agent or small molecule additives to have sufficient time to migrate and diffuse to the interface, further optimizing the interface bonding.

[0031] In the mixing step of remaining fillers, the vulcanizing agent and accelerator will quickly initiate crosslinking reactions at high temperatures, so they must be added last at low temperature and mixed quickly to retain sufficient processing safety time.

[0032] In the hot-pressing vulcanization forming step, under high temperature and high pressure, the vulcanizing agent reacts with the unsaturated bond on the molecular chain of the ethylene-propylene-diene rubber under the activation of the accelerator and the processing aid to form a stable three-dimensional elastomer network, which is the chemical basis for the material to obtain the final mechanical properties. High pressure forces the rubber to fill the mold, expels bubbles, and makes the material inside dense and defect-free.

[0033] In a third aspect, the application provides a preparation method of the flame-retardant ethylene-propylene-diene rubber material, and application of the flame-retardant ethylene-propylene-diene rubber material in the wire and cable industry, the construction industry, and the high-end equipment industry.

[0034] In summary, the application has at least one of the following beneficial technical effects: The flame retardant generates acid compounds during heating, and these acidic substances can dehydrate and carbonize the polymer matrix to form a dense and strong expanded carbon layer. At the same time, the decomposition of aluminum hydroxide produces water vapor and non-combustible gas, which dilutes the concentration of combustible substances produced by the polymer combustion, and the newly generated inorganic oxide layer not only serves as a good thermal protection layer to protect the underlying matrix from damage, but also helps to catalyze carbonization. The chemically formed carbon layer provides a substrate for the attachment and interweaving of carbon layer enhancers, which can penetrate, support, and reinforce the entire carbon layer, effectively preventing the carbon layer from breaking and peeling under the scouring of hot gas flow, and building a strong physical-chemical composite barrier. The catalytic synergist, on the one hand, catalyzes the earlier and more complete dehydration and cyclization of the polymer in the condensed phase, and cooperates with the phosphorus-based acid source to form a denser and stronger carbon layer. On the other hand, in the gas phase, its decomposition products can promote the oxidation of smoke particles, significantly reducing smoke density. The catalytic synergist can also interact with the aluminum oxide produced by the decomposition of aluminum hydroxide and the carbon layer material at high temperatures, promoting the formation of a dense composite ceramic phase on the surface of the carbon layer. Not only can it efficiently reflect radiant heat, but also can perfectly seal the micro-cracks and pores of the carbon layer, greatly improving the integrity and thermal insulation of the barrier.

[0035] The four components self-assemble into a protective layer with a multi-layer structure on the material combustion surface through precise cooperation. This protective layer has excellent thermal insulation, oxygen barrier, thermal shock resistance, and mechanical strength, and its formation process covers all temperature stages from the initial fire to the intense combustion, realizing seamless relay in time and composite reinforcement in space. The nonlinear synergistic effect of multiple mechanisms and multiple components makes the flame-retardant efficiency and fire resistance integrity of the material far exceed the simple addition of individual component mechanisms, achieving unexpected excellent results. DETAILED DESCRIPTION

[0036] The application will be further described in detail below in conjunction with the examples.

[0037] The materials used in the following examples can be obtained by market purchase.

[0038] Example 1: This example provides a flame-retardant ethylene propylene diene rubber material and a preparation method thereof.

[0039] The flame-retardant ethylene propylene diene rubber material includes, by weight fraction, 55 parts of ethylene propylene diene rubber, 20 parts of HT-802 aluminum hypophosphite, 5 parts of aluminum hydroxide, 2 parts of sulfur, 2 parts of polysilicic ester, 1 part of organic montmorillonite, 2 parts of accelerator CZ, and 2 parts of a compound of stearic acid and zinc oxide with a mass ratio of 1:3.

[0040] The preparation method of the flame-retardant ethylene propylene diene rubber material includes the following steps: S1, rubber plasticizing: placing the ethylene propylene diene rubber on a rubber precision mill, and opening the ethylene propylene diene rubber from high to low until it is smooth by adjusting the distance; S2, mixing of functional fillers: adjusting the roll gap to 3 mm, keeping the rubber on the roll to form a uniform stack, and adding the processing aids, aluminum hydroxide, HT-802 aluminum hypophosphite, polysilicic ester, and organic montmorillonite in sequence, slowly, and in batches under slow stirring, left and right cutter, and triangular bag mixing for 20 min; S3, thin pass refining and homogenization: gradually reducing the roll gap to 0.5 mm, thin passing the rubber for 4 times, then widening the roll gap to form smooth sheets, discharging the sheets, obtaining the masterbatch, and cooling to room temperature and standing for 6 h; S4, mixing of remaining fillers: re-refining the standing masterbatch on the mill, adding the vulcanizing agent and accelerator after the roll is smooth, quickly mixing uniformly within 5 min by using small feeding, left and right cutter, and triangular bag mixing, and quickly discharging the sheets to obtain the final refined rubber; S5, hot press vulcanization molding: cutting the final refined rubber into the required mass and shape, filling into a mold preheated to 180°C, placing on a flat vulcanization machine, vulcanizing under a pressure of 20 MPa for 15 min, and quickly cooling after demolding to obtain the flame-retardant ethylene propylene diene rubber material #1.

[0041] Example 2: This example provides a flame-retardant ethylene propylene diene rubber material and a preparation method thereof.

[0042] The flame-retardant ethylene propylene diene rubber material includes, by weight fraction, 75 parts of ethylene propylene diene rubber, 30 parts of a mixture of melamine cyanurate and dioctyl phthalate with a mass ratio of 1.3:1, 15 parts of aluminum hydroxide, 3 parts of sulfur, 6 parts of silicone resin, 3 parts of zinc borate, 4 parts of accelerator CZ, and 4 parts of a compound of stearic acid and zinc oxide with a mass ratio of 1:5.

[0043] The preparation method of the flame-retardant EPDM material #2 is the same as that of example 1.

[0044] Example 3: The present example provides a flame-retardant EPDM material and a preparation method thereof.

[0045] The flame-retardant EPDM material comprises, by weight fraction, 70 parts of EPDM, 25 parts of a mixture of HT-802 aluminum hypophosphite, melamine cyanurate, dioctyl phthalate and piperazine pyrophosphate in a mass ratio of 9:16:13:12, 10 parts of aluminum hydroxide, 2 parts of sulfur, 4 parts of expandable graphite, 2 parts of zinc molybdate, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0046] The preparation method of the flame-retardant EPDM material #3 is the same as that of example 1.

[0047] Example 4: The present example provides a flame-retardant EPDM material and a preparation method thereof.

[0048] The flame-retardant EPDM material comprises, by weight fraction, 70 parts of EPDM, 25 parts of a mixture of HT-802 aluminum hypophosphite and piperazine pyrophosphate in a mass ratio of 1:2, 10 parts of aluminum hydroxide, 2 parts of sulfur, 4 parts of expandable graphite, 2 parts of zinc molybdate, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0049] The preparation method of the flame-retardant EPDM material #4 is the same as that of example 1.

[0050] Example 5: The present example provides a flame-retardant EPDM material and a preparation method thereof.

[0051] The flame-retardant EPDM material comprises, by weight fraction, 70 parts of EPDM, 25 parts of a mixture of HT-802 aluminum hypophosphite and piperazine pyrophosphate in a mass ratio of 1:2, 10 parts of modified aluminum hydroxide, 2 parts of sulfur, 4 parts of expandable graphite, 2 parts of zinc molybdate, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0052] The preparation method of the flame-retardant EPDM material comprises the following steps: S1, preparation of modified aluminum hydroxide: after hydrolysis of silane coupling agent in an acidic alcohol aqueous solution, dry aluminum hydroxide powder is subjected to high-speed stirring reaction at 100°C for 40 min, the mass of the silane coupling agent is 2.0% of the mass of the aluminum hydroxide, and then the modified aluminum hydroxide is obtained by drying and crushing; S2, plasticizing of raw rubber: the EPDM is placed on a rubber precision mill, and the EPDM is milled from high to low until it is smooth by adjusting the distance. S3, mixing of functional fillers: the roll gap is adjusted to 3 mm, and the rubber compound is kept on the rolls to form a uniform stack. Under slow stirring, the processing aids, aluminum hydroxide, flame retardant, carbon layer enhancer, catalytic synergist are added in sequence, slowly and in batches. The left and right cutters are used, and the triangular package is punched. Mixing is carried out for 20 min; S4, thin pass refining and homogenization: the roll gap is gradually reduced to 0.5 mm, and the rubber compound is subjected to 4 thin passes. Then the roll gap is widened to the extent that the rubber compound can form smooth sheets. The sheets are taken out, and the masterbatch is obtained. The masterbatch is cooled to room temperature and left to stand for 6 h; S5, mixing of remaining fillers: the masterbatch after standing is re-mixed on the open mill. After the roll is smooth, the vulcanizing agent and accelerator are added. The small feed, left and right cutters, and triangular package are used to mix uniformly within 5 min. The final compound is obtained by quickly taking out the sheets. S6, hot pressing vulcanization molding: the final compound is cut into the required mass and shape, and filled into a mold preheated to 180°C. The mold is placed on a flat vulcanization machine, and vulcanized at a pressure of 20 MPa for 15 min. After demolding, the flame-retardant ethylene propylene rubber material #5 is obtained by rapid cooling.

[0053] Comparative Example 1: This comparative example provides a comparative ethylene propylene rubber material D1, which is the same as Example 5, except that the comparative ethylene propylene rubber material includes, by weight fraction, 70 parts of ethylene propylene rubber, 25 parts of a mixture of HT-802 aluminum secondary phosphate and piperazine pyrophosphate in a mass ratio of 1:2, 10 parts of modified aluminum hydroxide, 2 parts of sulfur, 2 parts of zinc molybdate, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0054] Comparative Example 2: This comparative example provides a comparative ethylene propylene rubber material D2, which is the same as Example 5, except that the comparative ethylene propylene rubber material includes, by weight fraction, 70 parts of ethylene propylene rubber, 25 parts of a mixture of HT-802 aluminum secondary phosphate and piperazine pyrophosphate in a mass ratio of 1:2, 10 parts of modified aluminum hydroxide, 2 parts of sulfur, 4 parts of expandable graphite, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0055] Comparative Example 3: This comparative example provides a comparative ethylene propylene rubber material D3, which is the same as Example 5, except that the comparative ethylene propylene rubber material includes, by weight fraction, 70 parts of ethylene propylene rubber, 25 parts of a mixture of HT-802 aluminum secondary phosphate and piperazine pyrophosphate in a mass ratio of 1:2, 10 parts of modified aluminum hydroxide, 2 parts of sulfur, 3 parts of accelerator CZ, and 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0056] Comparative Example 4: This comparative example provides a comparative EPDM material D4, which is the same as Example 5, except that the comparative EPDM material includes, by weight fraction, 70 parts of EPDM, 60 parts of modified aluminum hydroxide, 2 parts of sulfur, 3 parts of accelerator CZ, 3 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0057] Comparative Example 5: This comparative example provides a comparative EPDM material D5, which is the same as Example 5, except that the comparative EPDM material includes, by weight fraction, 70 parts of EPDM, 12 parts of sulfur, 13 parts of accelerator CZ, 13 parts of a compound of stearic acid and zinc oxide in a mass ratio of 1:4.

[0058] Comparative Example 6: This comparative example provides a comparative EPDM material D6, which is the same as Example 5, except that ammonium polyphosphate is used instead of the mixture of HT-802 aluminum secondary phosphate and piperazine pyrophosphate.

[0059] The flame-retardant EPDM materials #1-#5 of Examples 1-5 and the comparative EPDM materials D1-D5 of Comparative Examples 1-5 were tested for vertical burning rating (UL 94), oxygen index (GB / T 2406.2), tensile strength (ASTM D412), and elongation at break (GB / T 528), and the test results are shown in Table 1.

[0060] wherein the flame-retardant test is in accordance with the UL-94 test standard. The flame-retardant test procedure is as follows: the sample size used is 125±5 mm x 13.0±0.5 mm x 1.6±0.5 mm, 5 samples are prepared, the samples are clamped in a vertical horizontal burning tester YG-SS-650, the burning program is set, the flaming time is 10 s, the flaming times is 2, the afterflame time (ti, t2) and afterglow time (t3) of each time are recorded, whether the afterflame and afterglow spread to the clamping fixture, and whether the burning drips ignite the cotton pad. The judgment standard for V-0 in the experiment is that: the afterflame time (ti, t2) of a single sample is ≤10 s; the total afterflame time (tf) is ≤50 s; the afterflame time plus the afterglow time (t2+t3) of a single test sample after the second application of the flame; the afterflame and afterglow do not spread to the clamping fixture; and the burning drips do not ignite the cotton. Wherein the total afterflame time tf: wherein: tf - total afterflame time, in seconds (s); ti - first afterflame time of the i-th sample, in seconds (s); t2 - second afterflame time of the i-th sample, in seconds (s).

[0061] Table 1 From the data of Examples 1-4 in Table 1, especially the data of Example 4, it can be seen that by reasonably matching the flame-retardant EPDM material, the flame-retardant EPDM material of the present application has excellent flame retardance and mechanical properties.

[0062] Compared with Example 4, Example 5 uses surface silane coupling agent modified aluminum hydroxide, and the obtained flame-retardant EPDM material #5 has more excellent properties than the flame-retardant EPDM material #4. This is because Compared with Comparative Example 1, Comparative Example 1 does not add a carbon layer enhancer, and the obtained comparative EPDM material D1 has poorer properties than the flame-retardant EPDM material #5. This is because the carbon layer enhancer can physically enhance the carbon layer structure and improve the heat and oxygen insulation performance. Expandable graphite expands to form a carbon layer when heated, physically isolating heat and flammable gas, and interweaving with chemical carbon layers to enhance.

[0063] Compared with Comparative Example 2, Comparative Example 2 does not add a catalytic synergist, and the obtained comparative EPDM material D2 has poorer properties than the flame-retardant EPDM material #5. This is because the catalytic synergist can catalyze charring, smoke suppression, and promote flame-retardant reactions. Zinc molybdate can catalyze polymer dehydrogenation and cyclization, promote early charring and good charring, and inhibit smoke generation in the gas phase.

[0064] Example 5 compared with Comparative Example 3, Comparative Example 3 did not add carbon layer enhancer and catalytic synergist. Example 5 compared with Comparative Example 4, Comparative Example 4 did not add flame retardant, carbon layer enhancer and catalytic synergist. Example 5 compared with Comparative Example 5, Comparative Example 5 did not add modified aluminum hydroxide, flame retardant, carbon layer enhancer and catalytic synergist. The above comparative ternary ethylene-propylene rubber material does not have the performance of the flame-retardant ternary ethylene-propylene rubber material #5. This is because the acidic compound produced by the thermal decomposition of aluminum hypophosphite and other phosphorus-nitrogen flame retardants catalyzes the dehydration and crosslinking of the polymer matrix, forming a preliminary expanded carbon layer skeleton. At the same time, the modified aluminum hydroxide decomposes endothermically, reducing the surface temperature of the material by absorbing a large amount of heat, and releasing water vapor to dilute flammable gases, and the residual aluminum oxide particles embedded in the preliminary carbon layer enhance the thermal stability of the carbon layer. Expandable graphite expands rapidly along the crystal axis direction by tens to hundreds of times when heated, forming a worm-like, high-strength expanded carbon body. The chemically formed carbon layer provides a substrate for the physical expansion of graphite, and the tough network formed by the expanded graphite penetrates, supports and reinforces the entire carbon layer, effectively preventing the carbon layer from being broken and peeled off under the scouring of hot gas flow, and building a strong physical-chemical composite barrier. Zinc molybdate, on the one hand, catalyzes the polymer to dehydrate and cyclize earlier and more fully in the condensed phase, and cooperates with the phosphorus acid source to promote the formation of a carbon layer with higher graphitization degree and more dense and strong; on the other hand, in the gas phase, its decomposition products can promote the oxidation of smoke particles, significantly reducing the smoke density. Zinc molybdate can interact with the aluminum oxide produced by the decomposition of aluminum hydroxide at high temperatures, as well as carbon layer materials, to promote the formation of a dense, glassy molybdenum-aluminum-silicate composite ceramic phase on the surface of the carbon layer. This ceramic phase not only can efficiently reflect radiant heat, but also can perfectly seal the micro-cracks and pores of the carbon layer, greatly improving the integrity and thermal insulation of the barrier. The four components work together to form a protective layer with a multi-layer structure on the material combustion surface. The protective layer has excellent thermal insulation, oxygen barrier, thermal shock resistance and mechanical strength, and its formation process covers all temperature stages from the initial fire to the intense combustion, realizing seamless relay in time and composite reinforcement in space. The nonlinear synergistic effect of multiple mechanisms and multiple components makes the flame-retardant efficiency and fire resistance integrity of the material far exceed the simple addition of each component mechanism, achieving unexpected excellent results.

[0065] Example 5 compared with Comparative Example 6, Comparative Example 6 uses ammonium polyphosphate instead of the mixture of HT-802 aluminum hypophosphite and piperazine pyrophosphate, and the performance of the comparative ternary ethylene-propylene rubber material D6 is not as good as that of the flame-retardant ternary ethylene-propylene rubber material #5. This is because ammonium polyphosphate has poor dispersion in ternary ethylene-propylene rubber, low carbon formation efficiency and easy migration and precipitation, resulting in unstable flame-retardant effect and large mechanical loss.

[0066] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, so: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A flame-retardant EPDM rubber material, characterized in that, By weight, the flame-retardant EPDM rubber material comprises 55-75 parts EPDM rubber, 20-30 parts flame retardant, 5-15 parts aluminum hydroxide, 2-3 parts vulcanizing agent, 2-6 parts char layer reinforcing agent, 1-3 parts catalytic synergist, 2-4 parts accelerator, and 2-4 parts processing aid.

2. The flame-retardant EPDM rubber material according to claim 1, characterized in that, The flame retardant includes any one or more of HT-802 aluminum hypophosphate, melamine cyanurate, dioctyl phthalate, and piperazine pyrophosphate.

3. The flame-retardant EPDM rubber material according to claim 1, characterized in that, The carbon layer reinforcing agent is any one of expandable graphite, silicone resin, and polysilsesquioxane.

4. The method for preparing a flame-retardant EPDM rubber material according to claim 1, characterized in that, The catalytic synergist is any one of zinc molybdate, zinc borate, or organomontmorillonite.

5. The method for preparing a flame-retardant EPDM rubber material according to claim 1, characterized in that, The aluminum hydroxide is aluminum hydroxide with a surface modified by a silane coupling agent. The processing steps include: hydrolyzing the silane coupling agent in an acidic alcoholic aqueous solution, and then reacting it with dry aluminum hydroxide powder at 80-110°C with high-speed stirring for 30-60 minutes. The mass of the silane coupling agent is 1.0-3.0% of the mass of the aluminum hydroxide. Then, the mixture is dried and pulverized to obtain the modified aluminum hydroxide.

6. The method for preparing a flame-retardant EPDM rubber material according to claim 1, characterized in that, The vulcanizing agent is sulfur, the accelerator is accelerator CZ, and the processing aid is a compound of stearic acid and zinc oxide in a mass ratio of 1:3-5.

7. A method for preparing a flame-retardant EPDM rubber material as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: Raw rubber plasticizing: Place EPDM rubber on a precision rubber mill and grind the EPDM rubber from high to low by adjusting the distance until it is smooth; Mixing of functional fillers: Adjust the roller gap to 2-3mm to keep the rubber compound forming a uniform accumulation on the roller. Under slow stirring, add the processing aid, aluminum hydroxide, flame retardant, carbon layer enhancer, and catalytic synergist in sequence, slowly and in batches. Use left and right cutters and make triangular wraps, and mix for 15-20 minutes. Thin-pass refining and homogenization: Gradually reduce the roller gap to 0.5-1.0 mm and pass the rubber compound through the thin pass 3-5 times. Then widen the roller gap until the rubber compound can form a smooth sheet. The sheet is then produced to obtain the masterbatch. It is cooled to room temperature and left to stand for 4-6 hours. Mixing of remaining fillers: The masterbatch that has been left to stand is re-milled on the open mill. After the roll wrapping is smooth, vulcanizing agent and accelerator are added. Using a small amount of material, left and right cutters, and triangular wrapping method, it is quickly mixed evenly within 3-5 minutes and then quickly sheeted to obtain the final rubber. Hot-press vulcanization molding: The final compound is cut into the required mass and shape, filled into a mold preheated to 170-180℃, placed on a flat vulcanizing machine, and vulcanized for 10-20 minutes under a pressure of 15-20 MPa. After demolding, it is rapidly cooled to obtain the flame-retardant EPDM rubber material.

8. The application of a flame-retardant EPDM rubber material in the wire and cable industry, construction industry, and high-end equipment industry, characterized in that... Flame-retardant EPDM rubber material prepared using the preparation method of flame-retardant EPDM rubber material as described in any one of claims 1-6 or as described in claim 7.

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