Halogen-free flame-retardant EPDM composite foam material and preparation method thereof

Abstract

The invention discloses a halogen-free flame-retardant EPDM (Ethylene-Propylene-Diene Monomer) composite foam material and a preparation method thereof, and belongs to the field of polymer composite foam materials. The preparation method comprises the following steps: preparing a melamine polyphosphate flame retardant by taking melamine and strong phosphoric acid as raw materials, and coating melamine polyphosphate with aluminum hydroxide and magnesium hydroxide to obtain the core-shell structure flame retardant. And compounding the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide fiber to form a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, and preparing the halogen-free flame-retardant EPDM composite foaming material from the obtained composite flame retardant and EPDM by adopting a double-roller open milling and mold pressing foaming method. The obtained halogen-free flame-retardant EPDM composite foam material has excellent mechanical properties, thermal stability and flame retardance, can realize rapid surface carbon formation during a combustion test, has a strong smoke suppression effect, and greatly improves the molten drop phenomenon.

Description

Technical Field

[0001] The present invention belongs to the field of polymer composite foam materials, and specifically relates to a halogen-free flame-retardant EPDM composite foam material and a preparation method thereof. Background Art

[0002] Ethylene Propylene Diene Monomer (EPDM) is a copolymer obtained by curing and granulating ethylene, propylene and a small amount of a third monomer. It is a type of ethylene-propylene rubber. According to the different third monomers added, EPDM can be divided into the following three types: 1,4-hexadiene type (HD-EPDM), dicyclopentadiene type (DCPD-EPDM) and ethylidene norbornene type (ENB-EPDM). Its molecular structure is linear and double bonds are introduced in its side chain, so it can be vulcanized with sulfur or peroxides such as diisopropylbenzene peroxide; according to the different propylene content in EPDM, it can be divided into high propylene, medium propylene and low propylene types. At the same time, the higher the propylene content in the main body, the more the elastic properties and mechanical properties of EPDM vulcanizate decrease. The main chain of the polymer is composed of soft segments and hard segments embedded in each other. Among the many types of synthetic rubber materials, ethylene propylene diene monomer (EPDM) exhibits high elasticity of traditional rubber at room temperature and plasticity of ordinary plastic at high temperature, combining the characteristics of both plastic and rubber. EPDM has high production efficiency and can use common processing technologies of thermoplastics, such as melt blending extrusion molding. EPDM has excellent chemical stability, electrical insulation, aging resistance and waterproof performance, good ductility, high strength and high filling and plasticizing ability. It is now widely used in automotive engineering, construction engineering, air conditioning, refrigeration and other industries.

[0003] However, EPDM has a fatal flaw in use. Its oxygen index is usually only 18-23%. It decomposes and releases toxic gases such as CO during combustion, and serious dripping occurs during the combustion process, accompanied by relatively thick black smoke. The flammability of the material itself needs to be improved so that it can be used more conveniently. The material needs to be made difficult to burn by functional modification in terms of flame retardancy. The addition of flame retardants can make EPDM rubber materials extinguish faster during the combustion process, slow down the self-decomposition of the material, and greatly reduce the release of flammable gases and toxic components. Its reasonable use can reduce fire losses.

[0004] Commonly used flame retardant elements include halogen elements, N, P, B, Al, etc. Among them, commercial flame retardants are mainly halogen flame retardants. However, halogen flame retardants will release toxic gases and a large amount of smoke when ignited by open flames at high temperatures, which will cause serious pollution to the environment. Therefore, the development of a new type of flame retardant that is efficient, non-toxic and environmentally friendly has become the direction of development in the field of flame retardants. Summary of the invention

[0005] The object of the present invention is to provide a halogen-free flame-retardant EPDM composite foam material, which has good flame-retardant effect and processing performance.

[0006] To achieve the above object, the present invention adopts the following technical solution: A halogen-free flame-retardant EPDM composite foam material comprises, by weight, 100 parts of EPDM particles, 5-15 parts of a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, 5-10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of azodicarbonamide as a foaming agent, 0.5 parts of dicumyl peroxide as a cross-linking agent, and 2-4 parts of talc.

[0007] Furthermore, the preparation of the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant comprises the following steps: (1) Add melamine polyphosphate to 200 mL of deionized water, ultrasonically shake at 25°C until uniformly dispersed, then transfer to a 60°C water bath and continue magnetic stirring; (2) Slowly adding aluminum hydroxide and magnesium hydroxide to the solution obtained in step (1) in batches, stirring the mixture in a water bath for 4 hours, and then stirring the mixture at room temperature for another 4 hours before allowing it to stand overnight; (3) the reaction solution obtained in step (2) is centrifuged and the precipitate is dried to obtain a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant; (4) The melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant obtained in step (3) and the polyphenylene sulfide fiber are added into a mortar and ground and mixed evenly to obtain a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant.

[0008] Furthermore, the preparation method of the melamine polyphosphate is as follows: 12.6 g of melamine is added to 200 mL of deionized water at 95° C. and stirred for 10 min until dispersed, 11.5 mL of 85 wt.% concentrated phosphoric acid is slowly added in batches, and stirring is continued for 1.5 h until the reaction is complete. After the reactant is cooled to room temperature, it is filtered, the filter cake is washed with deionized water and placed in a vacuum drying oven at 80° C. for 4 h to obtain melamine polyphosphate.

[0009] Furthermore, the mass ratio of melamine polyphosphate, aluminum hydroxide and magnesium hydroxide is 8:1:1.

[0010] Furthermore, the temperature of the water bath in step (2) is 60°C.

[0011] Furthermore, the drying temperature in step (3) is 60° C. and the drying time is 10 h.

[0012] Furthermore, in step (4), the mass ratio of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant to polyphenylene sulfide fiber is 9:1.

[0013] The present invention also provides a method for preparing the flame-retardant EPDM composite foam material, comprising the following steps: (1) EPDM, melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, carbon black, zinc oxide, stearic acid, foaming agent, crosslinking agent and talc are uniformly mixed in a preheated two-roll mill for 10-20 minutes at a heating temperature of 50-60°C. After the rubber material is completely mixed, it is thinly passed 4-6 times to obtain a 2-4 mm rubber sheet; (2) After the rubber sheet obtained in step (2) is air-dried for 4-6 hours, it is placed in the mold cavity of a preheated flat-plate molding machine, and molded and foamed for 450 seconds at 175° C. and 10 MPa. After cooling, a halogen-free flame-retardant EPDM composite foam material is obtained.

[0014] The beneficial effects of the present invention are: (1) The present invention adopts melamine and phosphoric acid as raw materials to prepare melamine polyphosphate, and prepares melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant by coprecipitation method with aluminum hydroxide, magnesium hydroxide and polyphenylene sulfide fiber, and applies it to EPDM composite foaming material. The formula is scientific and reasonable, the process flow is practical and simple, and the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant is prepared in a green and environmentally friendly way, so that the prepared EPDM composite foaming material has the benefits of health and environmental protection.

[0015] (2) The melamine polyphosphate prepared by the present invention contains abundant N and P elements in its structure. The N-containing part will be thermally decomposed after being heated, releasing non-flammable gases such as NH3 and N2, which plays a role in diluting the concentration of oxygen and combustible gases; at the same time, the P-containing part can decompose and migrate to the surface of the polymer, playing a role in catalyzing carbonization and enhancing the surface carbon layer. In addition, due to the introduction of a ring structure in the structure, the compatibility with the EPDM matrix is ​​improved, overcoming the shortcomings of traditional nitrogen flame retardants that are easy to agglomerate in the matrix and have poor compatibility with the matrix, and maintaining good flame retardant properties.

[0016] (3) The melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant prepared by the present invention has a nitrogen ring structure that is friendly to inorganic materials and forms a core-shell structure with hydroxide, and combines it with the added polyphenylene sulfide fiber to form a simple combination. The combination of each component allows the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant to be used as a flame retardant and a reinforcing agent at the same time. The polyphenylene sulfide fiber itself is a short rod-shaped fiber that can be evenly dispersed in the EPDM matrix with the help of the core-shell structure, so that the stress distribution is uniform, thereby improving the tensile strength of the EPDM composite foam material. The compound use of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant and carbon black forms a new synergistic flame retardant system, which can overcome the shortcomings of EPDM foam materials that are flammable, easy to melt and easy to produce smoke when burned. When the 15% EPDM composite foam material of this flame retardant system burns, the polymer surface can quickly become carbonized without any burning phenomenon; after the fire source is removed, it can quickly self-extinguish and has a strong smoke suppression effect; and while significantly improving the flame retardant properties of the EPDM composite foam material, it also maintains the original mechanical properties of the EPDM composite foam material to the greatest extent.

[0017] (4) Melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant is used as a flame retardant additive for EPDM composite foaming materials. The amount added is small, the compatibility with the EPDM matrix material is good, it is easy to disperse, and it has excellent mechanical properties and flame retardant properties. EPDM composite foaming materials have the advantages of light weight, low density, good elasticity, etc. At the same time, it also provides new ideas and explorations for the preparation of composite flame retardants and foaming materials by green methods, and has huge social and economic benefits and development prospects in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the melamine polyphosphate prepared in the present invention.

[0019] Figure 2 This is the FTIR graph of the melamine polyphosphate prepared in the present invention.

[0020] Figure 3 This is a SEM image of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide prepared in the present invention.

[0021] Figure 4 This is a SEM image of the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant prepared by the present invention.

[0022] Figure 5 This is the SEM image of Example 3 of the flame retardant EPDM foam material prepared in the present invention. DETAILED DESCRIPTION

[0023] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0024] A preparation method of melamine polyphosphate comprises the following steps: Add 200 mL of deionized water and 12.6 g of melamine into a three-necked flask at 95°C. Stir for 10 min until highly dispersed. Then slowly add 11.5 mL of concentrated phosphoric acid (85 wt.%) in batches. Continue stirring for 1.5 h until the reaction is complete. After the reactants are cooled to room temperature, filter them. Wash the filter cake with deionized water and dry it in a vacuum drying oven at 80°C for 4 h to obtain white crystals of melamine polyphosphate.

[0025] Figure 1 This is a SEM image of the melamine polyphosphate prepared in the present invention. It can be seen that the prepared melamine polyphosphate presents an agglomerated and stacked morphology. Figure 2 FTIR image of melamine polyphosphate prepared in the present invention, 619cm -1 The deformation vibration absorption peak of NH2 is 1654cm -1 , 1550cm -1 , 1467cm -1 and 1404cm -1 The peak at 3419cm is the ring stretching vibration absorption peak; -1 and 3135cm -1 Symmetric and antisymmetric stretching vibration absorption peaks of NH appeared at 1350 cm -1 The P-OH symmetric stretching vibration peak appeared at , indicating that melamine polyphosphate was successfully synthesized.

[0026] The preparation of a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant comprises the following steps: (1) Weigh 8 g of melamine polyphosphate and add it to a 200 mL beaker of deionized water. Ultrasonicate at 25 °C until the mixture is evenly dispersed. Transfer the beaker to a 60 °C water bath and continue magnetic stirring. (2) Weigh 1 g of aluminum hydroxide and 1 g of magnesium hydroxide, slowly add them to the mixed solution prepared in step (1) in batches, and continue to stir and react in a water bath at 60°C for 4 h. Then take the beaker out of the water bath and continue to stir for 4 h and then let it stand overnight; (3) The mixed solution after the reaction is completed is centrifuged to obtain a white precipitate, and the obtained white precipitate is placed in a vacuum drying oven at 60° C. and dried for 10 hours to obtain a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant.

[0027] Figure 3 This is a SEM image of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide prepared in the present invention.

[0028] Example 1 A method for preparing a flame retardant EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 5 parts of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were mixed for 20 minutes using a double-roll mill preheated to 50°C until all the raw materials were evenly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0029] Example 2 A method for preparing a flame retardant EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were mixed for 20 minutes using a double-roll mill preheated to 50°C until all the raw materials were evenly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0030] Example 3 A method for preparing a flame retardant EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 15 parts of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were mixed for 20 minutes using a double-roll mill preheated to 50°C until all the raw materials were evenly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated film cavity of a flat vulcanizer, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0031] Comparative Example 1 A method for preparing an EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were mixed for 20 minutes using a double-roll mill preheated to 50°C until all the raw materials were evenly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0032] Comparative Example 2 A method for preparing an EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of melamine polyphosphate, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were uniformly mixed using a double-roll mill. After the raw materials were fully mixed, the mixed raw materials were pressed and mixed for 20 minutes using a double-roll mill preheated to 50°C until all the raw materials were uniformly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0033] Comparative Example 3 A method for preparing an EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of melamine, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were uniformly mixed using a double-roll mill preheated to 50°C for 20 minutes. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0034] Comparative Example 4 A method for preparing an EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of doped flame retardant (mixed by 8 parts of melamine polyphosphate, 1 part of aluminum hydroxide, 1 part of magnesium hydroxide, and 1 part of polyphenylene sulfide fiber), 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of crosslinking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were uniformly mixed using a double-roll mill preheated to 50°C for 20 minutes. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated film cavity of a flat vulcanizer, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0035] Comparative Example 5 A method for preparing an EPDM composite foam material comprises the following steps: 1) 100 parts of EPDM particles, 10 parts of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant, 10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of foaming agent AC (azodicarbonamide), 0.5 parts of cross-linking agent DCP (diisopropylbenzene peroxide), and 4 parts of talcum powder were uniformly mixed using a double-roll mill. After the raw materials were fully mixed, the mixed raw materials were pressed and mixed using a double-roll mill preheated to 50°C for 20 minutes until all the raw materials were uniformly mixed. After the raw materials were fully mixed, the mixed raw materials were pressed into 4 mm thin slices using a double-roll mill, and the raw material slices were placed in a blast drying oven and dried for 5 hours; 2) The thin sheet prepared in step 1) is placed in a preheated flat vulcanizer film cavity, and is molded and foamed for 450 seconds under the conditions of 10 MPa and 175° C., and then taken out to obtain a halogen-free flame-retardant composite foam material.

[0036] The samples obtained in the embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0037] Table 1 Sample performance test results The data in Table 1 show that when the addition amount of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant reaches 15 parts, the limiting oxygen index of the sample can reach 29.5, and the UL-94 grade is V-0. And with the increase of the addition amount of the composite flame retardant, the tensile strength and elongation at break of the sample are also improved to a certain extent, which shows that the composite flame retardant used in the present invention can also effectively improve the mechanical properties of the sample. Compared with Comparative Example 1 without adding the composite flame retardant, Comparative Example 2 with only 10 parts by weight of melamine polyphosphate added, and Comparative Example 4 with 10 parts by weight of doped flame retardant added (mixed by 8 parts of melamine polyphosphate, 1 part of aluminum hydroxide, 1 part of magnesium hydroxide, and 1 part of polyphenylene sulfide fiber), the flame retardant effect of the EPDM composite foam material prepared in Example 2 is significantly improved, indicating that the prepared melamine polyphosphate / aluminum hydroxide / magnesium hydroxide core-shell microsphere flame retardant and polyphenylene sulfide fiber play a synergistic flame retardant role, achieving the effect of 1+1>2. Moreover, the polyphenylene sulfide fiber itself is a short rod-shaped fiber, which can be evenly dispersed in the EPDM matrix with the help of the core-shell structure, so that the stress distribution is uniform, thereby improving the tensile strength of the EPDM composite foam material (Comparative Example 5). The present invention uses melamine polyphosphate, magnesium hydroxide and aluminum hydroxide to prepare a core-shell flame retardant material MMA, rather than simply superimposing several raw materials. At the same time, polyphenylene sulfide fiber is added to the synthesized core-shell material instead of a simple polyphenylene sulfide granular resin. After combining the two, a composite flame retardant is obtained, in which the polyphenylene sulfide fiber is responsible for toughening and partial flame retardant performance improvement. The core-shell flame retardant MMA exhibits a flame retardant effect that is better than ordinary doping due to its special inner and outer spherical structure. Figure 4 The electron microscope image of the synthesized core-shell flame retardant is shown in Figure 2. Due to the use of the "ball-stick"-like additive shape, the mechanical properties of the base material after foaming can be further enhanced. In addition, the comparative example 3 in which only 10 parts by weight of melamine is added is prepared, and the flame retardant effect is not as good as that of the embodiment 2 and the comparative example 2, indicating that the melamine polyphosphate prepared by the present invention can achieve a better flame retardant effect. Figure 5 It can be clearly seen that the composite flame retardant prepared by the present invention can be well dispersed in the EPDM composite foam material, so that the prepared final product has excellent flame retardant effect and mechanical properties.

[0038] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A halogen-free flame-retardant EPDM composite foam material, characterized in that: The halogen-free flame-retardant EPDM composite foaming material comprises, by weight: 100 parts of EPDM particles, 5-15 parts of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, 5-10 parts of carbon black, 2 parts of zinc oxide, 2 parts of stearic acid, 6 parts of azodicarbonamide, a cross-linking agent, 0.5 parts of diisopropyl peroxide, and 2-4 parts of talc.

2. The halogen-free flame-retardant EPDM composite foam material according to claim 1, characterized in that: The preparation of the melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant comprises the following steps: (1) Add melamine polyphosphate to 200 mL of deionized water, ultrasonically shake at 25°C until uniformly dispersed, then transfer to a 60°C water bath and continue magnetic stirring; (2) Slowly adding aluminum hydroxide and magnesium hydroxide to the solution obtained in step (1) in batches, stirring the mixture in a water bath for 4 hours, and then stirring the mixture at room temperature for another 4 hours before allowing it to stand overnight; (3) the reaction solution obtained in step (2) is centrifuged and the precipitate is dried to obtain a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant; (4) The melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant obtained in step (3) and the polyphenylene sulfide fiber are added into a mortar and ground and mixed evenly to obtain a melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant.

3. The method for preparing the halogen-free flame-retardant EPDM composite foam material according to claim 2, characterized in that: The preparation method of the melamine polyphosphate is as follows: 12.6 g of melamine is added to 200 mL of deionized water at 95° C. and stirred for 10 min until dispersed, 11.5 mL of 85 wt.% concentrated phosphoric acid is slowly added in batches, and stirring is continued for 1.5 h until the reaction is complete, and the reactant is cooled to room temperature and then filtered, and the filter cake is washed with deionized water and placed in a vacuum drying oven at 80° C. for 4 h to obtain melamine polyphosphate.

4. The method for preparing the halogen-free flame-retardant EPDM composite foam material according to claim 2, characterized in that: The mass ratio of melamine polyphosphate, aluminum hydroxide and magnesium hydroxide is 8:1:

1.

5. The method for preparing the halogen-free flame-retardant EPDM composite foam material according to claim 2, characterized in that: The temperature of the water bath in step (2) is 60°C.

6. The method for preparing the halogen-free flame-retardant EPDM composite foam material according to claim 2, characterized in that: The drying temperature in step (3) is 60° C. and the drying time is 10 h.

7. The method for preparing the halogen-free flame-retardant EPDM composite foam material according to claim 2, characterized in that: In step (4), the mass ratio of melamine polyphosphate / aluminum hydroxide / magnesium hydroxide microsphere core-shell flame retardant to polyphenylene sulfide fiber is 9:

1.

8. The method for preparing a flame retardant EPDM composite foam material according to claim 1, characterized in that: The following steps are involved: (1) EPDM, melamine polyphosphate / aluminum hydroxide / magnesium hydroxide / polyphenylene sulfide composite flame retardant, carbon black, zinc oxide, stearic acid, foaming agent, crosslinking agent and talc are uniformly mixed in a preheated two-roll mill for 10-20 minutes at a heating temperature of 50-60°C. After the rubber material is completely mixed, it is thinly passed 4-6 times to obtain a 2-4 mm rubber sheet; (2) After the rubber sheet obtained in step (2) is air-dried for 4-6 hours, it is placed in the mold cavity of a preheated flat-plate molding machine, and molded and foamed for 450 seconds at 175° C. and 10 MPa. After cooling, a halogen-free flame-retardant EPDM composite foam material is obtained.

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