High-toughness flame-retardant silicone rubber / nylon composite elastomer material and preparation method thereof

Abstract

The invention discloses a high-toughness flame-retardant silicone rubber / nylon composite elastomer material and a preparation method thereof, and solves the technical problems that in the prior art, traditional thermosetting silicone rubber is poor in mechanical property and has the risk of cracking when used in wires and cables. The material is prepared from the following raw materials: silicone rubber compound, nylon elastomer, N-P compound flame retardant, bio-based fatty acid ester plasticizer, flame retardant synergist, phase structure regulator and the like. By optimizing the formula design, the defects that the processing flow of traditional thermosetting silicone rubber is long and leftover materials are unrecyclable are overcome, the vertical combustibility of the prepared composite elastomer material UL94 reaches the V-0 level, and the composite elastomer material has excellent mechanical property, flame retardant property, processability and oil resistance. The method can be widely applied to the technical field of thermoplastic elastomer materials.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoplastic elastomer materials, in particular to a high-toughness flame-retardant silicone rubber / nylon composite elastomer material and a preparation method thereof. Background Art

[0002] In the wire and cable industry, the performance of the outer sheath material directly determines the safety, reliability, and environmental adaptability of the product. Traditional silicone rubber, as a mainstream material, has excellent high and low temperature resistance, electrical insulation, and physiological inertness. However, traditional silicone wires use thermosetting silicone rubber. The curing process of this type of material is an irreversible chemical cross-linking reaction, resulting in a lengthy processing process, high energy consumption, and the scrap cannot be recycled due to the irreversible cross-linking network. In addition, the mechanical properties of silicone rubber itself have inherent defects. Its tear strength is low, and the surface is prone to cracking in scenarios where the cable is frequently bent and rubbed. This is especially true in dynamic service environments such as high-voltage cables for new energy vehicles and high-speed data transmission cables, where the reliability risk is significantly increased.

[0003] Thermoplastic elastomers, through their unique segment structure, can effectively improve the toughness of materials. When blended with silicone rubber, they are expected to improve the mechanical properties of silicone rubber. However, the following problems exist in the blending of thermoplastic elastomers and silicone rubber: (1) When polar elastomers are directly blended with non-polar silicone rubber, macrophase separation is easily formed, resulting in a decrease in mechanical properties. (2) It is difficult for a single flame retardant to simultaneously meet the UL94 V-0 flame retardancy rating and low hardness requirements at low addition levels. (3) Traditional plasticizers (such as phthalates) are prone to migration, resulting in an increase in hardness during long-term use.

[0004] Chinese patent CN106751736A discloses a silicone rubber / polyurethane thermoplastic elastomer and its preparation method. The elastomer is prepared by blending polyurethane thermoplastic elastomer (TPU) with silicone rubber. The elastomer has good heat resistance, friction resistance and mechanical properties. However, according to its performance test results, its flame retardant properties and mechanical properties cannot meet the requirements of high-quality cable products. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a high-toughness flame-retardant silicone rubber / nylon composite elastomer material and a preparation method thereof. The present invention overcomes the defects of traditional thermosetting silicone rubber, such as the lengthy processing flow and non-recyclable scraps. The prepared composite elastomer material has a UL94 vertical flammability rating of V-0 and has excellent mechanical properties, flame retardancy, processing performance and oil resistance.

[0006] To achieve the above objectives, in a first aspect, an embodiment of the present invention provides a high-toughness flame-retardant silicone rubber / nylon composite elastomer material, comprising the following raw materials in parts by mass: 100 parts of silicone rubber compound, 80-155 parts of nylon elastomer, 55-85 parts of NP compound flame retardant, 15-30 parts of bio-based fatty acid ester plasticizer, 7-20 parts of flame retardant synergist, 7-20 parts of phase structure regulator, 5-10 parts of nano-montmorillonite, 1-3 parts of cross-linking agent, 0.5-1 part of initiator, 0.2-0.5 parts of antioxidant, 0.8-1.6 parts of UV inhibitor, and 0.2-0.5 parts of lubricant. The silicone rubber compound is methyl vinyl silicone rubber with a Shore hardness of 20A-40A and a vinyl content of 0.1%; The nylon elastomer is composed of 70 parts to 130 parts of TPAE-based polyamide copolymer and 10 parts to 25 parts of MBPA multi-block polyamide copolymer, and the Shore hardness of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is 25D to 35D; The phase structure regulator includes 5 to 15 parts of ethylene-α-olefin copolymer-g-MAH and 2 to 5 parts of aminosilane coupling agent.

[0007] In the embodiment of the present invention, the molecular weight of the methyl vinyl silicone rubber is about 400,000, and the silicone rubber compound can be selected from Wacker Chemical, Shin-Etsu Chemical KE-103, and Dow Corning SYLGARD184.

[0008] Preferably, the hard segment of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is PA12 and the soft segment is PTMG, the number of blocks of the TPAE-based polyamide copolymer is 2, and the number of blocks of the MBPA multi-block polyamide copolymer is ≥12.

[0009] In an embodiment of the present invention, TPAE-based polyamide copolymer serves as a basic component of nylon elastomer to ensure the basic mechanical properties and processing fluidity of the material. TPAE-based polyamide copolymers may include Evonik Degussa Pebax® 1657, Arkema PEBAX MV1074, and DuPont Zytel® PEBA 3533. MBPA multi-block polyamide copolymers disperse stress concentration through a multi-block structure of ≥12 segments, further improving the toughness and fatigue resistance of the material. MBPA multi-block polyamide copolymers may include Evonik Degussa Pebax® 1657, Arkema PEBAX RV3056, and Toray PEBASOL 5533.

[0010] Preferably, the NP compound flame retardant is a compound of piperazine pyrophosphate and melamine polyphosphate in a mass ratio of 2:1; and the flame retardant synergist is a polyketone resin.

[0011] In an embodiment of the present invention, piperazine pyrophosphate releases polyphosphoric acid during combustion to promote the formation of a carbon layer. Piperazine pyrophosphate can be selected from Jiangsu Yak Technology YAK-APP, Aiko Reagent AKnoka® NP820, and Shouguang Weidong Chemical WD-PP; melamine polyphosphate releases non-combustible gas to dilute oxygen and assist in the expansion of the carbon layer. Melamine polyphosphate can be selected from Zhejiang Wansheng Co., Ltd. WS-MPP, Guangzhou Jushi Chemical JSP-MPP, and Jiangsu Yak Technology YAK-MPP; polyketone resin acts as a flame retardant synergist to enhance the crosslinking density and heat resistance of the carbon layer, inhibit molten droplets and heat transfer, and can be selected from South Korea's Hyosung POK M330A and South Korea's Hyosung POK M23AG3A.

[0012] Preferably, the bio-based fatty acid ester plasticizer is at least one of castor oil-based fatty acid methyl ester, soybean oil-based fatty acid methyl ester, and palm oil-based fatty acid ethyl ester.

[0013] Preferably, the ethylene-α-olefin copolymer-g-MAH is an ethylene-octene copolymer-g-MAH with a grafting rate of 1.5%-2.0%.

[0014] In an embodiment of the present invention, ethylene-octene copolymer-g-MAH forms hydrogen bonds with polar groups of nylon elastomer through maleic anhydride groups, and ethylene segments are entangled with silicone rubber to improve the interfacial compatibility of the two phases. Ethylene-octene copolymer-g-MAH can be selected from Dow Chemical Engage G-1900, DuPont Elvaloy PTW, and Mitsui Chemicals TAFMER A3000; aminosilane coupling agent reacts with nylon through amino groups and condenses siloxane groups with silicone rubber to form chemical covalent bonds to strengthen interfacial bonding. Aminosilane coupling agent can be selected from Dow Corning Z-6011, Momentive A-1100, and Shin-Etsu KBM-603.

[0015] Preferably, the cross-linking agent includes at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or tert-butyl peroxyisopropyl carbonate.

[0016] Preferably, the initiator is tert-butyl peroxyisopropyl carbonate or dibenzoyl peroxide.

[0017] Preferably, the antioxidant is a 1:1 mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di-tert-butylphenyl)phosphite; The anti-UV agent is at least one of benzotriazole UV234 or benzophenone UV531.

[0018] Based on the requirements of high-toughness cable sheath, the basic system of the present invention selects methyl vinyl silicone rubber with a Shore hardness of 20A-40A as the flexible matrix and a compound nylon elastomer with a Shore hardness of 25D-35D as the rigid phase. The silicone rubber and nylon elastomer form an interpenetrating network structure through molecular chain entanglement and interfacial action, avoiding phase separation, so that stress is evenly transmitted in the two phases, reducing crack propagation, thereby synergistically improving the tensile strength, elongation at break and tear strength of the material. The prepared composite elastomer material has excellent mechanical properties.

[0019] In the nylon elastomer selected for this invention, the two-block TPAE structure offers a low glass transition temperature, providing foundational mechanical properties and ensuring the material possesses essential tensile strength and processing fluidity. The densely distributed hard segments of the multi-block MBPA structure disperse stress concentration, further enhancing the material's ductility and preventing embrittlement. Insufficient MBPA segments can compromise the material's mechanical properties. This combination of the two forms a uniformly dispersed "hard core-soft shell" structure within the silicone rubber matrix, significantly enhancing the toughness and fatigue resistance of the composite. The moderate hardness (25D-35D) balances rigidity and elasticity, enabling the nylon elastomer to serve as a reinforcing phase, enhancing the silicone rubber's strength without compromising its flexibility. If the hardness is too low, the hard segment microdomains will not form effective physical crosslinks; if it is too high, the soft segment fluidity will decrease, weakening the molecular entanglement with the silicone rubber.

[0020] To solve the phase separation problem between polar nylon and non-polar silicone rubber, the present invention improves interfacial tension through a bidirectionally compatible combination of ethylene-α-olefin copolymer-g-MAH and aminosilane coupling agent. Using either ethylene-α-olefin copolymer-g-MAH or aminosilane coupling agent as a compatibilizer alone is not ideal for improving the mechanical properties of composite elastomer materials.

[0021] To improve the flame retardant effect, the present invention uses a NP compound flame retardant in a specific ratio. When compounded at a ratio of 2:1, the nitrogen-phosphorus elements form a dual flame retardant mechanism of "gas phase dilution + condensed phase carbon layer", making the carbon layer denser and the flame retardant efficiency higher than the effect of using a single component. The flame retardant synergist polyketone resin promotes the cross-linking of the carbon layer, improves the strength and heat resistance of the carbon layer, prevents the transfer of molten droplets and heat, and synergizes with the NP system to improve the flame retardant grade and reduce the effective addition amount of the flame retardant. The introduction of nano-montmorillonite into the formula further enhances the dispersibility of the flame retardant in the matrix. At the same time, the layered structure of montmorillonite can inhibit the diffusion of molten droplets and smoke during combustion, synergistically improving the flame retardant performance.

[0022] The bio-based fatty acid ester plasticizer used in the present invention has better compatibility with silicone rubber and nylon elastomer, can be stably inserted between molecular chains, reduces the force between molecular chains and is not easy to migrate, thereby improving the flexibility and processing fluidity of the material. At the same time, the bio-based component is environmentally friendly.

[0023] In a second aspect, the present invention provides a method for preparing the composite elastomer material, comprising the following steps: (1) Premixing stage: Add silicone rubber compound, nylon elastomer, NP compound flame retardant, bio-based plasticizer, flame retardant synergist, phase structure regulator, and nano-montmorillonite into a high-speed mixer and mix at 80°C-100°C and 300-500 rpm for 30-40 minutes; (2) One-step extrusion: The premixed material from step (1) is fed into a twin-screw extruder, melt-blended at 180°C-220°C and a screw speed of 200 rpm-300 rpm, extruded through a die, and then water-cooled and granulated to obtain prepolymer pellets; (3) Secondary mixing: Add the prepolymer pellets, initiator, cross-linking agent, antioxidant, anti-UV agent and lubricant into an internal mixer, mix them at 100℃-120℃ and rotor speed of 50rpm-80rpm for 15min-20min, and extrude them into pellets again through a single screw extruder.

[0024] In a third aspect, the present invention provides the use of the above-mentioned composite elastomer material in the outer sheath of wires and cables.

[0025] Furthermore, the preparation process of the outer sheath of the wire and cable is as follows: the composite elastomer material is coated on the outer layer of the conductor through an extruder, and after cooling, an outer sheath with a thickness of 0.5 mm to 1.5 mm is formed.

[0026] The present invention has the following beneficial effects: The high-toughness flame-retardant silicone rubber / nylon composite elastomer material provided by the present invention significantly improves toughness through the synergy of silicone rubber compound and nylon elastomer in a specific ratio, overcoming the defect of low tear strength of traditional silicone rubber. By adopting NP compound flame retardant and polyketone resin to work together, UL94V-0 flame retardant grade can be achieved at a low addition amount, solving the problem that a single flame retardant is difficult to take into account both flame retardancy and low hardness. The two-way compatibilizer system effectively improves the compatibility of polar and non-polar components, avoiding the degradation of mechanical properties caused by phase separation. Bio-based fatty acid ester plasticizer replaces traditional plasticizers, reduces migration, and has little change in hardness after long-term use. At the same time, the material is a thermoplastic system, which simplifies the processing process, reduces energy consumption, and can recycle scraps, overcoming the processing and recycling problems of traditional thermosetting silicone rubber. In addition, the material also has excellent oil resistance, aging resistance and processing fluidity, and is suitable for the outer sheath of wires and cables with high quality requirements. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Traditional silicone rubber, as a mainstream material, offers excellent resistance to high and low temperatures, electrical insulation, and physiological inertness. However, conventional silicone cables utilize thermosetting silicone rubber, a material whose curing process involves an irreversible chemical cross-linking reaction. This results in lengthy processing, high energy consumption, and the inability to recycle scraps due to the irreversible cross-linking network. Furthermore, silicone rubber itself has inherent mechanical flaws. Currently, the tensile strength of silicone rubber materials is mostly between 6 and 10 MPa, making it susceptible to surface cracking when subjected to frequent bending and friction. This significantly increases reliability risks, especially in dynamic service environments such as high-voltage cables for new energy vehicles and high-speed data transmission cables.

[0029] The present invention provides a high-toughness flame-retardant silicone rubber / nylon composite elastomer material, which is composed of the following raw materials in parts by mass: 100 parts of silicone rubber compound, 80-155 parts of nylon elastomer, 55-85 parts of NP compound flame retardant, 15-30 parts of bio-based fatty acid ester plasticizer, 7-20 parts of flame retardant synergist, 7-20 parts of phase structure regulator, 5-10 parts of nano-montmorillonite, 1-3 parts of cross-linking agent, 0.5-1 part of initiator, 0.2-0.5 parts of antioxidant, 0.8-1.6 parts of UV inhibitor, and 0.2-0.5 parts of lubricant. The silicone rubber compound is methyl vinyl silicone rubber with a Shore hardness of 20A-40A and a vinyl content of 0.1%; The nylon elastomer is composed of 70 parts to 130 parts of TPAE-based polyamide copolymer and 10 parts to 25 parts of MBPA multi-block polyamide copolymer, and the Shore hardness of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is 25D to 35D; The phase structure regulator includes 5 to 15 parts of ethylene-α-olefin copolymer-g-MAH and 2 to 5 parts of aminosilane coupling agent.

[0030] Preferably, the hard segment of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is PA12 and the soft segment is PTMG, the number of blocks of the TPAE-based polyamide copolymer is 2, and the number of blocks of the MBPA multi-block polyamide copolymer is ≥12.

[0031] Preferably, the NP compound flame retardant is a compound of piperazine pyrophosphate and melamine polyphosphate in a mass ratio of 2:1; and the flame retardant synergist is a polyketone resin.

[0032] Preferably, the bio-based fatty acid ester plasticizer is at least one of castor oil-based fatty acid methyl ester, soybean oil-based fatty acid methyl ester, and palm oil-based fatty acid ethyl ester.

[0033] Preferably, the ethylene-α-olefin copolymer-g-MAH is an ethylene-octene copolymer-g-MAH with a grafting rate of 1.5%-2.0%.

[0034] Preferably, the cross-linking agent includes at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or tert-butyl peroxyisopropyl carbonate.

[0035] Preferably, the initiator is tert-butyl peroxyisopropyl carbonate or dibenzoyl peroxide.

[0036] Preferably, the antioxidant is a 1:1 mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (1010) and tris(2,4-di-tert-butylphenyl)phosphite (168); The anti-UV agent is at least one of benzotriazole UV234 or benzophenone UV531.

[0037] In order to illustrate the excellent effects of the present invention, the present invention has made the following examples and comparative examples.

[0038] The raw materials used in the following examples and comparative examples of the present invention can be purchased from the market, and their sources are not specifically limited.

[0039] The following raw material sources are illustrative: Silicone rubber compound, Wacker Chemical; TPAE-based polyamide, Evonik Degussa, brand Pebax® 1657; MBPA multi-block polyamide, Evonik Degussa, brand Pebax® 1657; Piperazine pyrophosphate, Jiangsu Yak Technology, brand YAK-APP; Melamine polyphosphate, Zhejiang Wansheng Co., Ltd., brand WS-MPP; POK flame retardant synergist, Hyosung, South Korea, brand POK M330A; Ethylene-α-olefin copolymer-g-MAH, Dow Chemical, brand Engage G-1900; Aminosilane coupling agent, Dow Corning, brand Z-6011; Bio-based fatty acid ester plasticizer, Wilmar International, brand BIO-Plasticizer C18; Nano-montmorillonite, Fenghong New Materials, brand FH-300; Crosslinker, bis-25 crosslinker, Akzo Nobel, brand Perkadox® 14; Antioxidant 1010:168, BASF, brand Irganox® 1010+168; Lubricant, Licowax PE 520; Anti-UV agent, Tinuvin 234.

[0040] The preparation methods of the silicone rubber / nylon composite elastomer materials of the following examples and comparative examples are as follows: (1) Raw material pretreatment The TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer are dried in a forced air drying oven at 80°C-100°C for 4h-6h until the moisture content is ≤0.1%; The nano-montmorillonite and 2% by weight of a silane coupling agent were mixed at 50° C.-60° C. and 100 rpm for 30 minutes for surface modification to improve the compatibility of the nano-montmorillonite with the matrix.

[0041] (2) Premixing stage Add silicone rubber compound (cut into 5cm³ small pieces), nylon elastomer (crushed to particle size <5mm), NP compound flame retardant, bio-based plasticizer, POK flame retardant synergist, phase structure regulator, and nano-montmorillonite into the mixer; To avoid volatilization of the plasticizer, set the temperature to 80-100°C, mix at 300 rpm for 10 minutes, then mix at high speed 500 rpm for 20-30 minutes until the material becomes uniform translucent granules.

[0042] (3) One-time extrusion Temperature settings for each section of the twin-screw extruder: Feeding section 180-190°C, melting section 190-210°C, mixing section 200-220°C, homogenizing section 210-220°C, die head temperature 220°C; The screw speed was 200-300 rpm (shear rate was controlled at 500-800 s⁻¹), the material residence time was 3-5 min, and after extrusion, it was cooled in a water bath (water temperature 25±2°C) and granulated (particle size 2-3 mm).

[0043] (4) Secondary mixing Add the prepolymer pellets, initiator, crosslinking agent (pre-mixed with peroxide and co-crosslinking agent), antioxidant, anti-UV agent and lubricant into the internal mixer; To avoid premature decomposition of peroxide, set the temperature to 100-120°C, the rotor speed to 50-80 rpm, and mix for 15-20 minutes until there are no obvious particles in the material; Transfer to a single-screw extruder, set the temperature to 160-190°C, the screw speed to 150 rpm, extrude into granules, and dry in a blast drying oven at 105°C. The moisture content of the finished granules is ≤0.1%. Example

[0044] The raw material components of Examples 1-10 are shown in Table 1, wherein the Shore hardness of the silicone rubber compound is 30A, the Shore hardness of the TPAE-based polyamide copolymer is 30D, and the Shore hardness of the MBPA multi-block polyamide copolymer is 30D and the number of blocks is 12.

[0045] Table 1

[0046] Comparative Example Comparative Example 1 The mass ratio of the TPAE-based polyamide copolymer to the MBPA multi-block polyamide copolymer is 80:0, and the rest is the same as in Example 1.

[0047] Comparative Example 2 The mass ratio of the TPAE-based polyamide copolymer to the MBPA multi-block polyamide copolymer is 48:32, and the rest is the same as in Example 1.

[0048] Comparative Example 3 Except that the Shore hardness of the MBPA multi-block polyamide copolymer is 20D, other aspects are the same as those of Example 1.

[0049] Comparative Example 4 Except that the Shore hardness of the MBPA multi-block polyamide copolymer is 40D, other aspects are the same as those of Example 1.

[0050] Comparative Example 5 The same procedures as in Example 1 were followed except that an MBPA multi-block polyamide copolymer with 8 blocks was used instead of an MBPA multi-block polyamide copolymer with 12 blocks.

[0051] Comparative Example 6 The same procedures as in Example 1 were followed except that 10 parts of ethylene-octene copolymer-g-MAH was added and no aminosilane coupling agent was added.

[0052] Comparative Example 7 Except for adding 5 parts of aminosilane coupling agent and not adding ethylene-octene copolymer-g-MAH, the other steps were the same as in Example 1.

[0053] Comparative Example 8 The same procedures as in Example 1 were followed except that non-grafted ethylene-octene copolymer was used instead of ethylene-α-olefin copolymer-g-MAH.

[0054] Comparative Example 9 Except for not adding nano-montmorillonite, the other steps are the same as those in Example 1.

[0055] Comparative Example 10 Except for using phthalate plasticizer instead of bio-based plasticizer, other procedures are the same as in Example 1.

[0056] Comparative Example 11 The same procedures as in Example 1 were followed except that 55 parts of piperazine pyrophosphate was added and melamine polyphosphate was not added.

[0057] Comparative Example 12 The same procedures as in Example 1 were followed except that 55 parts of melamine polyphosphate was added and piperazine pyrophosphate was not added.

[0058] Comparative Example 13 Except for using 55 parts of aluminum hydroxide instead of 55 parts of NP compound flame retardant, the rest is the same as Example 1.

[0059] Comparative Example 14 Except for using 82.5 parts of aluminum hydroxide to replace 55 parts of NP compound flame retardant, other procedures are the same as those in Example 1.

[0060] Test example The various properties and characterization methods of the materials in the present invention are as follows: Tensile strength: tested according to GB / T 528-2020; Elongation at break is tested according to GB / T 528-2020; Tear strength, tested according to GB / T 529-2008 standard; UL94 flame retardant rating, tested according to UL94-2021 (V-0 / V-1 rating, 1.6mm thickness); Shore A hardness, tested according to GB / T 531.1-2019 standard; Bending performance is tested according to GB / T 2951.4-2008; Density: tested according to GB / T 1033.1-2008 standard; Hardness change (30 days), tested according to GB / T 531.1-2019 standard; Melt flow rate: tested according to ISO1133 standard (230°C, 2.16kg); Oil resistance: Oil resistance conditions, IRM902, 60℃*168H.

[0061] The performance data of Examples 1-10 are shown in Table 2.

[0062] Table 2

[0063] The performance data of Comparative Examples 1-7 are shown in Table 3.

[0064] Table 3

[0065] The performance data of Comparative Examples 8-14 are shown in Table 4.

[0066] Table 4

[0067] It can be seen from the test results in Table 2 that the composite elastomer materials of Examples 1 to 10 of the present invention have excellent comprehensive properties, and their UL94 vertical flammability can reach V-0 level (1.6mm thickness), and the Shore A hardness is about 70, providing appropriate hardness support for the material. The tensile strength at break can reach about 18Mpa, the elongation at break is higher than 450%, and the tear strength is about 30kN / m. It has good bending properties and can withstand complex stress environments. It is suitable for fields such as wire and cable sheaths that require high material flexibility and durability. The low density ensures that the material is lightweight without affecting performance. The hardness change rate is small, ensuring good dimensional stability of the material. The melt flow rate is about 5g / 10min, to ensure that the material has good fluidity during processing and is easy to mold and process. The silicone rubber / nylon composite elastomer material of the present invention achieves synergistic optimization and comprehensive balance of flame retardant properties, mechanical properties, oil resistance and processing properties through specific components and proportions.

[0068] As can be seen from the test results in Table 3, when Example 1 is compared with Comparative Examples 1 to Comparative Examples 5, it can be seen that the ratio, hardness, and structure of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer play a key role in the mechanical properties of the material. An imbalance in the TPAE and MBPA ratio, a deviation in the MBPA hardness, or an insufficient number of MBPA blocks will affect the mechanical properties and flame retardancy of the material.

[0069] Comparison between Example 1 and Comparative Examples 6 and 7 shows that compared with Comparative Examples 6 and 7 using a single-component compatibilizer, the phase structure regulator of the present invention uses ethylene-α-olefin copolymer-g-MAH and aminosilane coupling agent to synergistically form a two-way compatibility, which has better mechanical properties and flame retardant properties.

[0070] As can be seen from the test results in Table 4, when compared with Comparative Example 8, it can be seen that the non-grafted ethylene-octene copolymer in Example 1 cannot effectively improve the interface, and the mechanical properties and flame retardant grade are poor. When compared with Comparative Example 9, it can be seen that nano-montmorillonite plays a key role in improving the flame retardant properties and oil resistance of the material. When compared with Comparative Example 10, it can be seen that the bio-based plasticizer has an important influence on the mechanical properties and oil resistance of the material. The hardness of Comparative Example 10 has increased significantly, which has an impact on the long-term flexibility and reliability of the material. When compared with Comparative Examples 11-12, it can be seen that the present invention uses a specific ratio of compound flame retardants to enable the material to obtain better flame retardant properties. Comparing Example 1 with Comparative Examples 13 and 14, it can be seen that the NP compound flame retardant used in the present invention has better flame retardant properties, mechanical properties, processing properties and oil resistance. Comparative Example 13 uses aluminum hydroxide of the same mass to replace the NP compound flame retardant, and the flame retardant property is V-2, and the burning time is prolonged, accompanied by the droplet phenomenon, and the flame retardant efficiency is significantly reduced; although Comparative Example 14 achieves the V-1 flame retardant grade by adding a large dose of aluminum hydroxide, it leads to a significant decrease in mechanical properties.

[0071] From the performance test results of the above embodiments and comparative examples, it can be seen that the composite elastomer materials of each embodiment of the present invention effectively achieve the synergistic improvement of high toughness, excellent flame retardant properties, good oil resistance and processing stability through the selection and combination of multiple raw materials.

[0072] Finally, it should be noted that the content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A high-toughness flame-retardant silicone rubber / nylon composite elastomer material, characterized in that: It is composed of the following raw materials in parts by mass: 100 parts of silicone rubber compound, 80-155 parts of nylon elastomer, 55-85 parts of NP compound flame retardant, 15-30 parts of bio-based fatty acid ester plasticizer, 7-20 parts of flame retardant synergist, 7-20 parts of phase structure regulator, 5-10 parts of nano-montmorillonite, 1-3 parts of cross-linking agent, 0.5-1 part of initiator, 0.2-0.5 parts of antioxidant, 0.8-1.6 parts of UV inhibitor, and 0.2-0.5 parts of lubricant. The silicone rubber compound is methyl vinyl silicone rubber with a Shore hardness of 20A-40A and a vinyl content of 0.1%; The nylon elastomer is composed of 70 parts to 130 parts of TPAE-based polyamide copolymer and 10 parts to 25 parts of MBPA multi-block polyamide copolymer, and the Shore hardness of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is 25D to 35D; The phase structure regulator includes 5 to 15 parts of ethylene-α-olefin copolymer-g-MAH and 2 to 5 parts of aminosilane coupling agent.

2. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The hard segment of the TPAE-based polyamide copolymer and the MBPA multi-block polyamide copolymer is PA12, and the soft segment is PTMG. The number of blocks of the TPAE-based polyamide copolymer is 2, and the number of blocks of the MBPA multi-block polyamide copolymer is ≥12.

3. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The NP compound flame retardant is a compound of piperazine pyrophosphate and melamine polyphosphate in a mass ratio of 2:1; and the flame retardant synergist is a polyketone resin.

4. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The bio-based fatty acid ester plasticizer is at least one of castor oil-based fatty acid methyl ester, soybean oil-based fatty acid methyl ester, and palm oil-based fatty acid ethyl ester.

5. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The ethylene-α-olefin copolymer-g-MAH is an ethylene-octene copolymer-g-MAH with a grafting rate of 1.5%-2.0%.

6. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The cross-linking agent includes at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or tert-butyl peroxyisopropyl carbonate.

7. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The initiator is tert-butyl peroxyisopropyl carbonate or dibenzoyl peroxide.

8. The silicone rubber / nylon composite elastomer material according to claim 1, characterized in that: The antioxidant is a 1:1 mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and tris(2,4-di-tert-butylphenyl) phosphite; The anti-UV agent is at least one of benzotriazole UV234 or benzophenone UV531.

9. A method for preparing the composite elastomer material according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Premixing stage: Add silicone rubber compound, nylon elastomer, NP compound flame retardant, bio-based plasticizer, flame retardant synergist, phase structure regulator, and nano-montmorillonite into a high-speed mixer and mix at 80°C-100°C and 300-500 rpm for 30-40 minutes; (2) One-step extrusion: The premixed material from step (1) is fed into a twin-screw extruder, melt-blended at 180°C-220°C and a screw speed of 200 rpm-300 rpm, extruded through a die, and then water-cooled and granulated to obtain prepolymer pellets; (3) Secondary mixing: Add the prepolymer pellets, initiator, cross-linking agent, antioxidant, anti-UV agent and lubricant into an internal mixer, mix them at 100℃-120℃ and rotor speed of 50rpm-80rpm for 15min-20min, and extrude them into pellets again through a single screw extruder.

10. Application of high-toughness flame-retardant silicone rubber / nylon composite elastomer material in the outer sheath of wires and cables, characterized in that: The high-toughness flame-retardant silicone rubber / nylon composite elastomer material is the high-toughness flame-retardant silicone rubber / nylon composite elastomer material according to any one of claims 1 to 8.

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