Insulating ethylene propylene diene monomer composite material and preparation method thereof

Abstract

The invention discloses an insulating ethylene propylene diene monomer composite material and a preparation method thereof, and belongs to the technical field of rubber preparation. The preparation method comprises the following steps: dispersing boron nitride in a dispersant, adding a coupling agent, and drying to obtain modified boron nitride; dispersing the modified boron nitride in polyisobutene in a molten state, freezing, crushing and sieving to obtain polyisobutene-boron nitride composite powder; mixing ethylene propylene diene monomer, the polyisobutene-boron nitride composite powder, a conductive agent and an antioxidant; and finally, adding a vulcanizing agent into the mixed system in S3, and vulcanizing to obtain the insulating ethylene propylene diene monomer composite material. The insulating ethylene propylene diene monomer composite material provided by the invention has excellent electrical insulation property and electrical resistance, and can effectively prevent electrical tree aging and prolong the service life of the product.

Description

Technical Field

[0001] The invention belongs to the field of rubber preparation, and particularly relates to an insulating EPDM rubber composite material and a preparation method thereof. Background Art

[0002] Ethylene propylene diene monomer (EPDM) rubber possesses excellent electrical insulation and corona resistance, with electrical properties superior to or approaching those of styrene-butadiene rubber, chlorosulfonated polyethylene, polyethylene, and cross-linked polyethylene. This is primarily due to the absence of polar substituents in its molecular structure, low cohesive energy, the ability of the molecular chain to maintain flexibility over a wide range, and low water absorption, resulting in excellent insulation properties.

[0003] However, EPDM's application in insulation still has some drawbacks and areas for improvement. As modern electronic equipment and high-voltage electrical systems continue to place increasing demands on insulation material performance, EPDM's insulation performance may not meet the requirements in complex environments such as high field strength and high humidity. Furthermore, EPDM's poor compatibility with other polar materials creates difficulties when preparing composite materials to enhance insulation performance. For example, when compounded with polar fillers or fibers, problems such as uneven dispersion and poor interfacial bonding may occur, affecting the overall insulation performance of the composite material. Summary of the Invention

[0004] Based on the deficiencies of the prior art, the present invention aims to provide an insulating EPDM rubber composite material and a preparation method thereof.

[0005] The first aspect of the present invention is to provide a method for preparing an insulating EPDM rubber composite material, comprising the following steps: S1: dispersing boron nitride in a dispersant, adding a coupling agent, and drying to obtain modified boron nitride; S2: dispersing the modified boron nitride in molten polyisobutylene, crushing the mixture under freezing conditions, and sieving the mixture to obtain polyisobutylene@boron nitride composite powder; S3: mixing EPDM rubber, polyisobutylene@boron nitride composite powder, conductive agent and antioxidant; S4: Add a vulcanizing agent to the S3 mixed system, and after vulcanization is completed, an insulating EPDM rubber composite material is obtained.

[0006] It should be noted that boron nitride (BN) is a highly insulating filler that can impart ultra-high volume resistivity and breakdown strength to the material, while also blocking electrical dendrite channels through its lamellar structure. Polyisobutylene (PIB) leverages its molecular chain similarity to ethylene propylene diene monomer (EPDM) to achieve interfacial capacity expansion. The PIB@BN core-shell structure obtained by the above method physically isolates BN agglomerates through PIB coating, improving dispersion and eliminating interfacial effects. The surface enrichment effect of PIB drives the BN to be evenly distributed at the rubber interface. BN forms a dense physical barrier layer on the rubber surface, blocking internal charge injection and inhibiting the initiation of electrical dendrites, thereby achieving long-term antistatic effect. In addition, the weak polarity and low surface energy state of the PIB molecular chain easily adsorb environmental moisture or ions, forming a directional surface charge migration channel, allowing charges to quickly migrate and dissipate across the interface, thereby reducing static electricity accumulation and achieving interfacial dielectric relaxation antistatic effect.

[0007] In some embodiments, the dispersant is selected from at least one of anhydrous ethanol and isopropyl alcohol; the coupling agent is selected from at least one of γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and vinyltriethoxysilane; the conductive agent is selected from one of carbon black and multi-walled carbon nanotubes; and the vulcanizing agent is selected from at least one of diisopropylbenzene peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0008] In some embodiments, the antioxidant is prepared by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0009] In some embodiments, boron nitride and the dispersant are mixed in a mass ratio of 1:8-12, and the boron nitride has a flaky structure.

[0010] In some embodiments, in S1, the drying temperature is 120-130° C., and the drying time is 3-4 h.

[0011] In some embodiments, in S2, the freezing condition is rapid cooling in liquid nitrogen at -20 to -30°C for 10-15 min; and the sieve has a mesh size of 400-450 mesh.

[0012] It should be noted that since PIB is in a viscous state at room temperature, wire drawing will occur when it is crushed at room temperature. The wire drawing and adhesion of the coating layer will cause the particle size to be out of control and form a cohesive block. At the same time, the shear force of mechanical crushing at room temperature will destroy the integrity of the BN sheet structure. Liquid nitrogen low-temperature crushing ensures that the BN sheet is peeled off along the PIB seam by brittle fracture, maintaining the sheet structure.

[0013] In some embodiments, in S3, the mixing temperature is 120-150° C., and the mixing time is 8-10 min.

[0014] In some embodiments, in S4, the vulcanization time is 10-20 min, and the vulcanization temperature is 50-70°C.

[0015] A second aspect of the present invention is to provide an insulating EPDM rubber composite material.

[0016] In some embodiments, by weight, the EPDM rubber is 100 parts, the boron nitride is 20-30 parts, the polyisobutylene is 8-12 parts, the conductive agent is 3-4 parts, the coupling agent is 2-4 parts, the antioxidant is 1-2 parts, and the vulcanizing agent is 2-3 parts.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention creatively combines modified boron nitride with polyisobutylene to form a polyisobutylene@boron nitride composite powder. Leveraging the excellent compatibility of polyisobutylene with EPDM rubber and its low surface energy, the polyisobutylene@boron nitride is evenly dispersed on the rubber surface, forming a dense physical barrier layer of boron nitride. This layer, utilizing the insulating properties of boron nitride, blocks charge injection, inhibits the initiation of electrical treeing, and achieves an insulating effect. Furthermore, polyisobutylene forms surface charge migration channels, enabling rapid charge transfer and dissipation, thereby reducing static electricity accumulation.

[0018] The insulating EPDM rubber composite material provided by the present invention has excellent electrical insulation performance and electrical resistance, can effectively prevent electrical tree aging, and extend the service life of the product, and can be widely used in the fields of cable insulation layers. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the embodiments.

[0020] Example 1 An insulating EPDM rubber composite material comprises, by weight, 100 parts of EPDM rubber, 25 parts of boron nitride, 10 parts of polyisobutylene, 4 parts of a conductive agent, 3 parts of a coupling agent, 2 parts of an antioxidant, and 3 parts of a vulcanizing agent.

[0021] The insulating EPDM rubber composite material is prepared by the following steps: S1: Flake boron nitride (source: Shandong Jingyi New Materials Co., Ltd.) was dispersed in anhydrous ethanol, γ-glycidyloxypropyltrimethoxysilane was added, and the mixture was dried at 125°C for 3.5 h to obtain modified boron nitride. The boron nitride and dispersant were mixed in a mass ratio of 1:10. S2: Dispersing the modified boron nitride in molten polyisobutylene, quenching in liquid nitrogen at -25°C for 12 min, and then crushing the mixture. The mixture was sieved through 450 mesh to obtain polyisobutylene@boron nitride composite powder. S3: mixing EPDM rubber, polyisobutylene@boron nitride composite powder, carbon black, and antioxidant at 120-150°C for 8-10 min; wherein antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1; S4: Dicumyl peroxide was added to the S3 mixture, and the mixture was vulcanized at 60°C for 15 minutes to obtain an insulating EPDM rubber composite material.

[0022] Example 2 It is basically the same as Example 1, with the only difference being that, by weight, the EPDM rubber is 100 parts, the boron nitride is 20 parts, the polyisobutylene is 8 parts, the conductive agent is 3 parts, the coupling agent is 2 parts, the antioxidant is 1 part, and the vulcanizing agent is 2 parts.

[0023] Example 3 The method is basically the same as Example 1, with the only difference being that, by weight, the EPDM rubber is 100 parts, the boron nitride is 30 parts, the polyisobutylene is 12 parts, the conductive agent is 4 parts, the coupling agent is 4 parts, the antioxidant is 2 parts, and the vulcanizing agent is 3 parts.

[0024] Example 4 It is basically the same as Example 1, with the only difference being: The insulating EPDM rubber composite material of this embodiment 4 is prepared by the following steps: S1: Dispersing flake boron nitride in isopropyl alcohol, adding γ-aminopropyltriethoxysilane, and drying at 120°C for 3 hours to obtain modified boron nitride; wherein the boron nitride and the dispersant are mixed in a mass ratio of 1:8; S2: Dispersing the modified boron nitride in molten polyisobutylene, quenching in liquid nitrogen at -20°C for 10 min, and then crushing the mixture. The mixture was sieved through 400 mesh to obtain polyisobutylene@boron nitride composite powder. S3: EPDM rubber, polyisobutylene@boron nitride composite powder, multi-walled carbon nanotubes, and antioxidant were mixed at 120°C for 8 min; wherein antioxidant 1010 and antioxidant 168 were compounded in a mass ratio of 1:1; S4: Add 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane to the S3 mixed system and vulcanize at 50°C for 10 min to obtain an insulating EPDM rubber composite material.

[0025] Example 5 It is basically the same as Example 1, with the only difference being: The insulating EPDM rubber composite material provided in this embodiment 5 is prepared by the following steps: S1: Dispersing flake boron nitride in anhydrous ethanol, adding vinyltriethoxysilane, and drying at 130°C for 4 hours to obtain modified boron nitride; wherein the boron nitride and the dispersant are mixed in a mass ratio of 1:12; S2: Dispersing the modified boron nitride in molten polyisobutylene, quenching in liquid nitrogen at -30°C for 15 min, and then crushing the mixture. The mixture was sieved through 450 mesh to obtain polyisobutylene@boron nitride composite powder. S3: EPDM rubber, polyisobutylene@boron nitride composite powder, carbon black and antioxidant were mixed at 150°C for 10 min; wherein antioxidant 1010 and antioxidant 168 were compounded in a mass ratio of 1:1; S4: Dicumyl peroxide was added to the S3 mixture, and the mixture was vulcanized at 70°C for 20 min to obtain an insulating EPDM rubber composite material.

[0026] Example 6 The process is basically the same as Example 1, except that the flake boron nitride is replaced with the same amount of spherical boron nitride.

[0027] Comparative Example 1 The preparation method is basically the same as Example 1, with the only difference being that S1 and S2 are omitted, and the polyisobutylene@boron nitride composite powder in S3 is replaced by flake boron nitride and polyisobutylene, that is, BN and PIB are physically blended rather than a PIB@BN core-shell structure.

[0028] Comparative Example 2 The process is basically the same as Example 1, except that polyisobutylene is replaced by the same amount of polymethyl methacrylate.

[0029] Comparative Example 3 Example 1 is basically the same, with the only difference being that the operation in S2, "quenching in liquid nitrogen at -25°C for 12 min" is changed to "cooling and crushing at room temperature (25°C)".

[0030] In order to verify that the insulating EPDM rubber composite material provided by the present invention has excellent insulation performance and good mechanical properties, the rubber composite materials prepared in Examples 1-5 and Comparative Examples 1-3 were tested below. The performance test results are shown in Table 1.

[0031] The tensile properties are tested according to GB / T1040.2-2022 at a tensile rate of 500 mm / min.

[0032] The tear strength was tested according to GB / T529-2008 at a tensile rate of 500 mm / min.

[0033] Shore hardness is tested according to GB / T531.1-2008.

[0034] The volume resistivity is tested according to GB / T 40719-2021.

[0035] The dielectric strength is tested according to GB / T 1695-2005.

[0036] Table 1 From the performance test data in Table 1, it can be seen that the rubber materials of Examples 1-5 all have high electrical insulation and excellent physical properties. In Example 6, the flake boron nitride was replaced with spherical boron nitride. There were gaps between the stacked spherical particles, which lacked a planar shielding effect and could not block the charge injection channel, resulting in a decrease in insulation performance. Combined with the comparative examples, it can be seen that the comparative examples used a blending method, and the rubber resistivity and dielectric strength were both reduced, indicating that the PIB@BN core-shell structure can greatly improve the resistivity of the rubber material. In Comparative Example 2, due to the extremely poor compatibility between polymethyl methacrylate and EPDM, BN was severely agglomerated, and the electrical resistance was also greatly reduced. Comparative Example 3 was cooled and crushed at room temperature to obtain a polyisobutylene@boron nitride composite powder, which destroyed the integrity of the BN layer structure and caused a decrease in the insulation performance of the rubber material.

[0037] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an insulating EPDM rubber composite material, characterized in that: The following steps are involved: S1: dispersing boron nitride in a dispersant, adding a coupling agent, and drying to obtain modified boron nitride; S2: dispersing the modified boron nitride in molten polyisobutylene, crushing the mixture under freezing conditions, and sieving the mixture to obtain a polyisobutylene@boron nitride composite powder; S3: mixing the EPDM rubber, the polyisobutylene@boron nitride composite powder, the conductive agent and the antioxidant; S4: adding a vulcanizing agent to the mixed system of S3, and obtaining the insulating EPDM rubber composite material after vulcanization is completed.

2. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: The dispersant is selected from at least one of anhydrous ethanol and isopropanol; the coupling agent is selected from at least one of γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and vinyltriethoxysilane; the conductive agent is selected from one of carbon black and multi-walled carbon nanotubes; and the vulcanizing agent is selected from at least one of diisopropylbenzene peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

3. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: The antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

4. The method for preparing the insulating EPDM rubber composite material according to claim 2, wherein: The boron nitride and the dispersant are mixed in a mass ratio of 1:8-12; the boron nitride has a flaky structure.

5. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: In the step S1, the drying temperature is 120-130° C. and the drying time is 3-4 h.

6. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: In the above S2, the freezing condition is rapid cooling in liquid nitrogen at -20 to -30°C for 10-15 min; and the mesh size of the sieve is 400-450 mesh.

7. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: In the step S3, the mixing temperature is 120-150° C., and the mixing time is 8-10 min.

8. The method for preparing the insulating EPDM rubber composite material according to claim 1, characterized in that: In the step S4, the vulcanization time is 10-20 min, and the vulcanization temperature is 50-70°C.

9. An insulating EPDM rubber composite material, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. The insulating EPDM rubber composite material according to claim 9, characterized in that: In parts by weight, the EPDM rubber is 100 parts, the boron nitride is 20-30 parts, the polyisobutylene is 8-12 parts, the conductive agent is 3-4 parts, the coupling agent is 2-4 parts, the antioxidant is 1-2 parts, and the vulcanizing agent is 2-3 parts.

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