Modified ethylene-propylene rubber composite material for high-speed train cable terminal and preparation method and use thereof

Abstract

The application provides a modified ethylene-propylene rubber composite material for a high-speed train cable terminal and a preparation method and application thereof, and relates to the technical field of cable insulation materials.The modified ethylene-propylene rubber composite material is prepared from the following raw materials in parts by weight: ethylene-propylene rubber 100 parts, polydopamine-coated ZnO and BaTiO3 composite nanoparticles 10-30 parts, reinforcing agent 20-40 parts, plasticizer 5-15 parts, anti-aging agent 1-5 parts, vulcanizing agent 1-5 parts, and vulcanization accelerator 1-5 parts.The modified ethylene-propylene rubber composite material prepared by the application has good nonlinear electric conductivity and dielectric properties, good corona resistance, and excellent mechanical properties, and meets the high-standard requirements of the insulation material for the vehicle-mounted cable terminal.

Description

Technical Field

[0001] This invention relates to the field of cable insulation materials technology, specifically to modified ethylene propylene rubber composite materials for high-speed train cable terminals, their preparation methods, and applications. Background Technology

[0002] With the rapid development of high-speed railway technology, the on-board high-voltage cable system, as a key component of train power transmission, directly affects the normal operation of the train and passenger safety. During high-speed train operation, the on-board high-voltage cable terminals, due to their unique structure, are prone to electric field concentration. Coupled with the harsh conditions of the on-board environment, such as severe vibration and high-low temperature cycling, this significantly accelerates the deterioration of the dielectric properties of the insulation material, leading to partial discharge or even breakdown faults, posing serious safety hazards to train operation.

[0003] Ethylene propylene diene monomer (EPDM) rubber, due to its highly saturated molecular structure, possesses excellent weather resistance, ozone resistance, electrical insulation properties, as well as good mechanical properties and economic efficiency, making it the preferred matrix material for stress control tubes in vehicle-mounted high-voltage cable terminations. Studies have shown that EPDM maintains good flexibility and electrical properties within a temperature range of -55℃ to 150℃, making it particularly suitable for applications in the drastically temperature-changing environments of vehicles. However, the dielectric constant of pure EPDM material is relatively low (typically between 3 and 4), making it difficult to effectively alleviate the electric field concentration problem at cable terminations.

[0004] To improve the dielectric properties of EPDM, existing technologies mainly use single ZnO or related composite particles (such as ZnO and SiO2) to modify EPDM. Although this method can improve the insulation performance of the material to some extent, it still has obvious drawbacks when facing the complex working conditions of vehicle-mounted cable terminals: such as poor conductivity and dielectric properties, easy particle agglomeration, poor dispersion stability, insufficient interfacial bonding, and poor service stability.

[0005] Therefore, there is a need to develop a better modified ethylene propylene rubber composite material for high-speed train cable terminals. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this invention is to provide a modified ethylene propylene rubber composite material for high-speed train cable terminals, its preparation method, and its applications.

[0007] This invention provides a modified ethylene propylene rubber composite material, which is prepared from the following raw materials in parts by weight:

[0008] 100 parts of ethylene propylene rubber, 10-30 parts of polydopamine-coated ZnO and BaTiO3 composite nanoparticles, 20-40 parts of reinforcing agent, 5-15 parts of plasticizer, 1-5 parts of anti-aging agent, 1-5 parts of vulcanizing agent, and 1-5 parts of vulcanization accelerator.

[0009] Furthermore, the aforementioned modified ethylene propylene rubber composite material is prepared from the following raw materials in parts by weight:

[0010] 100 parts of ethylene propylene rubber, 20 parts of polydopamine-coated ZnO and BaTiO3 composite nanoparticles, 30 parts of reinforcing agent, 10 parts of plasticizer, 1.5 parts of anti-aging agent, 2.0 parts of vulcanizing agent, and 1.0 part of vulcanization accelerator.

[0011] Furthermore, the mass ratio of ZnO nanoparticles to BaTiO3 nanoparticles in the polydopamine-coated ZnO and BaTiO3 composite nanoparticles is (3.5-4.5):1.

[0012] Preferably, the mass ratio of ZnO nanoparticles to BaTiO3 nanoparticles in the polydopamine-coated ZnO and BaTiO3 composite nanoparticles is 4:1.

[0013] Preferably, the ZnO nanoparticles have a particle size of 30 nm and a PDI of no more than 0.15; the nano-BaTiO3 has a particle size of 50 nm and a PDI of no more than 0.15.

[0014] Furthermore, the preparation method of the polydopamine-coated ZnO and BaTiO3 composite nanoparticles includes the following steps:

[0015] (1) ZnO nanoparticles and BaTiO3 nanoparticles were mixed in a certain mass ratio and then added to Tris-HCl buffer solution and sonicated to prepare a dispersion.

[0016] (2) Add dopamine hydrochloride to the dispersion and stir until a polydopamine coating layer is formed on the surface of ZnO nanoparticles and BaTiO3 nanoparticles;

[0017] (3) The nanoparticles obtained in step (2) are washed and dispersed in anhydrous ethanol solution to obtain a suspension. A silane coupling agent is added to the suspension to react and polydopamine-coated ZnO and BaTiO3 composite nanoparticles are obtained.

[0018] Furthermore,

[0019] In step (1), the mass-to-volume ratio of the total mass of ZnO nanoparticles and BaTiO3 nanoparticles to the volume of Tris-HCl buffer solution is 10g:100~500mL; preferably 10g:200mL.

[0020] And / or, in step (2), the mass of the dopamine hydrochloride is 1-5% of the total mass of the ZnO nanoparticles and BaTiO3 nanoparticles; preferably 4%;

[0021] And / or, in step (2), the stirring speed is 500 r / min, the stirring temperature is 20~30℃, and the stirring time is 6h;

[0022] And / or, in step (3), the concentration of nanoparticles in the suspension is 0.01~0.05 g / mL; preferably 0.02 g / mL;

[0023] And / or, in step (3), the mass of the silane coupling agent is 10-20% of the total mass of nano-ZnO and nano-BaTiO3; preferably 15%;

[0024] And / or, in step (3), the reaction temperature is 70~80℃, preferably 70℃, and the reaction time is 1~5h, preferably 2h.

[0025] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0026] Furthermore,

[0027] The reinforcing agent is selected from silica;

[0028] And / or, the plasticizer is selected from one or more combinations of paraffin oil and naphthenic oil;

[0029] And / or, the anti-aging agent is selected from p-phenylenediamine anti-aging agents;

[0030] And / or, the vulcanizing agent is selected from peroxide-based vulcanizing agents;

[0031] And / or, the vulcanization accelerator is selected from triallyl vulcanizing agents.

[0032] Furthermore,

[0033] The plasticizer is selected from paraffin oil;

[0034] And / or, the anti-aging agent is selected from N-isopropyl-N'-phenyl-p-phenylenediamine;

[0035] And / or, the vulcanizing agent is selected from dicumyl peroxide;

[0036] And / or, the vulcanization accelerator is selected from triallyl isocyanurate.

[0037] The present invention also provides a method for preparing the aforementioned modified ethylene propylene rubber composite material, comprising the following steps:

[0038] (a) Weigh each ingredient according to its weight;

[0039] (b) The raw materials are mixed in a gradient process to obtain a cooked rubber;

[0040] (c) The calcined rubber is vulcanized to obtain a modified ethylene propylene rubber composite material;

[0041] In step (b), the gradient mixing is divided into the following three stages:

[0042] (A-1) Add ethylene propylene rubber to a mixer and mix to form a uniform rubber matrix;

[0043] (A-2) Add the anti-aging agent, reinforcing agent and plasticizer to the system in step (A) in sequence, and mix.

[0044] (A-3) Add polydopamine-coated ZnO and BaTiO3 composite nanoparticles to the system in step (B), then add vulcanizing agent and vulcanization accelerator, and continue to mix to obtain gluten.

[0045] In step (c), the vulcanization is divided into the following two stages:

[0046] (B-1) After the granulated rubber is granulated, the first stage of vulcanization is carried out to make the rubber molecular chains initially cross-linked;

[0047] (B-2) Increase the vulcanization temperature to complete the crosslinking and obtain the composite material.

[0048] Furthermore,

[0049] In step (A-1), the mixing temperature is 90℃, the rotation speed is 40r / min, and the time is 0.5h;

[0050] And / or, in step (A-2), the mixing temperature is 80°C, the rotation speed is 50 r / min, and the time is 0.3 h;

[0051] And / or, in step (A-3), the mixing temperature is 70°C, the rotation speed is 30 r / min, and the time is 0.5 h;

[0052] And / or, in step (B-1), the vulcanization temperature is 150°C, the pressure is 10 MPa, and the time is 10 min;

[0053] And / or, in step (B-2), the vulcanization temperature is 170°C, the pressure is 10 MPa, and the time is 15 min.

[0054] The present invention also provides the use of the aforementioned modified ethylene propylene rubber composite material in the preparation of stress control tubes for vehicle-mounted high-voltage cable terminals.

[0055] In this invention, room temperature refers to 20~30℃.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] This invention utilizes nano-ZnO and nano-BaTiO3 to construct dual active centers, and through composite modification, controls the particle size distribution to 100-130nm (PDI≤0.15), effectively solving the problem of easy agglomeration of single ZnO particles. Simultaneously, the composite material prepared by modifying EPDM with a specific formula exhibits an interfacial bonding strength increased by more than 35%, preventing interfacial delamination under vehicle vibration. Furthermore, the composite material prepared by the specific formula of this invention has a high nonlinear coefficient, high corona initiation voltage, extended corona resistance life, low dielectric loss factor, and good mechanical properties, maintaining a performance retention rate of ≥95% under harsh operating conditions. The overall solution achieves synergistic improvement in multiple properties of modified EPDM, offering significant advantages over existing single ZnO modification or other composite filler modification technologies, and fully meeting the insulation requirements of vehicle cable terminals.

[0058] In summary, the modified ethylene propylene rubber composite material prepared by this invention has good nonlinear conductivity and dielectric properties, good corona resistance, and excellent mechanical properties, meeting the requirements of high-speed train cables and showing good application prospects.

[0059] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0060] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Detailed Implementation

[0061] The raw materials and equipment used in the specific embodiments of the present invention are all known products, obtained by purchasing commercially available products.

[0062] The nano-ZnO and nano-BaTiO3 used in this embodiment are both commercially available products purchased directly, and their parameters are guaranteed by the supplier's technical specifications. The chemical purity of the nano-ZnO is not less than 99.5%, and the total impurity ion content is less than 0.1%. The chemical purity of the nano-BaTiO3 is not less than 99.5%, and the impurity content is controlled below 0.1%. The ethylene propylene diene monomer (EPDM) rubber is a commercially available product purchased directly, specifically Sinopec Mitsui EPDM 2060M. EPDM is provided in granular or strip form and is vacuum-dried at 60°C for 8 hours before use.

[0063] Example 1: Preparation of the modified ethylene propylene rubber composite material for high-speed train cable terminals according to the present invention

[0064] The preparation method of the modified ethylene propylene rubber composite material for high-speed train cable terminals of the present invention includes the following steps:

[0065] S101, Preparation and Pretreatment of Combined Particle Raw Materials

[0066] Specifically, nano-ZnO and nano-BaTiO3 were selected as the core raw materials for dual active centers. The two types of nanoparticles underwent pretreatment: the nanoparticles were placed in a vacuum drying oven and dried at 80℃ for 12 hours to remove surface-adsorbed moisture and trace organic impurities; subsequently, nanoparticles with uniform particle size distribution (30 nm for nano-ZnO, PDI 0.12; 50 nm for nano-BaTiO3, PDI 0.13) were screened using an airflow sieving method to ensure consistency in subsequent composite modification. The pretreated particles were sealed and stored to prevent re-adsorption of moisture or contamination, laying the foundation for subsequent surface modification.

[0067] S102, Polydopamine (PDA) Modification Treatment of Composite Particles

[0068] Specifically, pretreated nano-ZnO (8g) and nano-BaTiO3 (2g) were mixed at a mass ratio of 4:1 and placed in 200mL of Tris-HCl buffer solution. An ultrasonic dispersion device was then used for dispersion to ensure initial uniform dispersion of the particles. Dopamine hydrochloride (0.4g), representing 4% of the total mass of nano-ZnO and nano-BaTiO3, was added to the dispersion. The mixture was placed on a magnetic stirrer and stirred continuously at 500r / min for 6 hours at room temperature. Utilizing the self-polymerization properties of dopamine, a uniform PDA coating layer was formed on the particle surface, resulting in PDA-coated ZnO / BaTiO3 composite nanoparticles.

[0069] S103, Silane Coupling Agent Composite Modification of Combined Particles

[0070] Specifically, the PDA-coated composite particles were filtered and washed to remove unreacted dopamine hydrochloride, and then dispersed in 300 mL of anhydrous ethanol solution to prepare a homogeneous suspension (the concentration of composite particles in the suspension was 0.02 g / mL). A silane coupling agent, γ-aminopropyltriethoxysilane (1.5 g), was added to the suspension. The mass of the silane coupling agent was 15% of the total mass of nano-ZnO and nano-BaTiO3. After stirring, the mixture was heated to 70 °C and maintained at this temperature for 2 h. This allowed the active groups in the coupling agent molecules to react with the functional groups on the surface of the PDA coating layer, introducing specific chemical bonds onto the particle surface. After the reaction, the particles were filtered, washed, and dried in a vacuum drying oven to constant weight, obtaining the PDA-coupling agent composite modified composite particles (PDA-KH550 composite modified ZnO / BaTiO3 composite nanoparticles). Fourier transform infrared spectroscopy (FTIR) characterization verified the modification effect, confirming the successful composite modification.

[0071] S104, EPDM matrix pretreatment and composite formulation

[0072] Specifically, EPDM, suitable for cable terminals, was selected as the matrix material and placed in a vacuum drying oven at 60°C for 8 hours to remove internally adsorbed moisture and volatile impurities, preventing the formation of bubbles or interface defects during the mixing process. Simultaneously, vulcanizing agents, vulcanization accelerators, anti-aging agents, reinforcing agents, plasticizers, and other additives were pretreated (solid additives were sieved or manually removed, and liquid additives were filtered) to remove mechanical impurities and ensure additive purity. Moisture-absorbing additives were dried using conventional low-temperature drying methods to prevent moisture from affecting the vulcanization effect and the material's insulation performance. The types of additives and the formulations for preparing the composite material are shown in Table 1.

[0073] Table 1. Types of additives and formulations for preparing composite materials

[0074]

[0075] S105, gradient mixing to prepare composite materials

[0076] Specifically, a gradient mixing process is employed using an internal mixer, with material mixing completed in three stages to ensure that the modified composite particles are uniformly dispersed in the EPDM matrix: Stage 1: The pretreated EPDM matrix is ​​added to the internal mixer, and the temperature (90℃) and rotation speed (40 r / min) are set for 0.5 hours to fully soften the EPDM and form a uniform rubber matrix. Stage 2: The internal mixer temperature is lowered to the set value (80℃), and the rotation speed is increased (50 r / min). Anti-aging agents, reinforcing agents, and plasticizers are added sequentially, and the mixture is stirred for 0.3 hours to ensure that the additives are uniformly dispersed in the EPDM matrix, preventing localized aggregation. Stage 3: The internal mixer temperature (70℃) and rotation speed (30 r / min) are further adjusted, and the functional filler modified composite particles are slowly added, followed by vulcanizing agents and vulcanization accelerators. The mixture is stirred at low speed until the material is free of obvious particles and has a uniform color. The mixing continues for 0.5 hours to strengthen the interfacial bonding between the particles and the matrix, preventing secondary particle agglomeration and obtaining a cured rubber. The mixing effect is judged by observing the appearance of the materials during the mixing process to ensure that there are no agglomerates or interface cracks inside the composite material.

[0077] S106, segmented vulcanization molding process

[0078] Specifically, the mixed quenched rubber is removed, granulated using a granulator, and then placed in a flat vulcanizing machine for segmented vulcanization molding: First-stage vulcanization: The first-stage vulcanization temperature is set at 150℃ and the pressure at 10MPa, held for 10 minutes to allow the rubber molecular chains to initially cross-link, fixing the distribution position of particles in the matrix and preventing particle migration and aggregation during subsequent vulcanization; Second-stage vulcanization: The vulcanization temperature is adjusted to a higher level (170℃), while maintaining the pressure, and held for another 15 minutes to allow the cross-linking reaction to proceed fully, strengthening the interfacial bonding force between particles and the matrix, and improving the mechanical properties and insulation stability of the composite material. After vulcanization, it is naturally cooled to room temperature and demolded to obtain the composite material required for the stress control tube of the vehicle-mounted cable terminal. The composite material can be designed into different test sizes according to subsequent performance testing requirements.

[0079] The following specific experimental examples demonstrate the beneficial effects of the present invention.

[0080] Experimental Example 1: Characterization and Screening of Modified Composite Particles

[0081] I. Experimental Methods

[0082] (I) Screening of parameters in the PDA adsorption-bridging modification stage

[0083] Using ZnO / BaTiO3 composite nanoparticles as the research object, the mass ratio of ZnO to BaTiO3 was fixed at 4:1, and the total mass of the composite particles was 10g. The composite particles were dispersed in deionized water, and an initial uniform dispersion system (the concentration of composite particles was 0.02 g / mL) was obtained under ultrasonic dispersion conditions.

[0084] Based on this, different amounts of dopamine hydrochloride were added to the dispersion system. By adjusting the amount of dopamine hydrochloride, stirring speed, and adsorption time (as shown in Table 2), the adsorption-bridging modification conditions of PDA on the surface of the composite particles were screened. Utilizing the hydrogen bonding between the abundant hydroxyl groups in PDA and the hydroxyl groups on the surface of the composite particles, PDA is adsorbed onto the particle surface and forms a stable interfacial bridging layer, thereby improving the dispersion stability of the composite particles.

[0085] Table 2. Parameter Screening Scheme for PDA Adsorption-Bridging Modification Stage

[0086]

[0087] Screening criteria:

[0088] Particle size distribution index (PDI) ≤ 0.15;

[0089] TEM observation showed that the coating layer was continuous and there were no obvious exposed particles;

[0090] The absolute value of the zeta potential is ≥25mV.

[0091] (II) Screening of parameters in the modification stage of silane coupling agents

[0092] Based on the combined particles with the best PDA adsorption-bridging effect, the modification conditions of the silane coupling agent were further screened. The concentration of the combined particles was fixed at 0.02 g / mL and dispersed in 300 mL of anhydrous ethanol. The amount of KH550, reaction temperature and reaction time were adjusted (as shown in Table 3) to obtain the composite modified particles with the best interfacial bonding performance.

[0093] Table 3. Screening scheme for parameters in the modification stage of silane coupling agents

[0094]

[0095] Screening criteria:

[0096] The FTIR spectrum shows characteristic peaks for Si-O-Si and -NH2 corresponding to KH550;

[0097] TGA measurements showed that the weight gain of the organic coating layer was 2-6%;

[0098] The particles showed no significant sedimentation or aggregation when left to stand in anhydrous ethanol for 24 hours.

[0099] II. Test Results

[0100] The particle size distribution, dispersibility, surface chemical structure and thermal stability of the modified composite particles prepared according to the different parameters described in the experimental example were tested, and the screening results are as follows.

[0101] (I) Screening results of the PDA adsorption-bridging modification stage

[0102] The particle size distribution and dispersion stability test results of the combined particles under different PDA adsorption-bridging modification parameters are shown in Table 4.

[0103] Table 4. Dispersion performance test results of combined particles under different PDA adsorption-bridging modification parameters

[0104]

[0105] Results analysis:

[0106] When the amount of dopamine hydrochloride was 0.40 g, the stirring speed was 500 r / min, and the adsorption time was 6 h (A5 group), the particle size distribution of the composite particles was the most concentrated, the D50 was the smallest (112 nm), the PDI was the lowest (0.12), and the absolute value of the ζ potential was the largest (32.4 mV). This indicates that under these conditions, PDA molecules formed a relatively stable adsorption-bridging structure on the surface of the composite particles, which effectively improved the dispersion stability of the particles and inhibited the aggregation behavior.

[0107] (II) Screening Results of the Silane Coupling Agent Modification Stage

[0108] Based on the optimal conditions for PDA adsorption-bridging modification (Group A5), the surface structure and thermal stability of the combined particles under different KH550 modification conditions were tested, and the results are shown in Table 5.

[0109] Table 5. Characterization results of the composite particles under different silane coupling modification conditions

[0110]

[0111] Results analysis:

[0112] When the amount of KH550 was 1.5g, the reaction temperature was 70℃, and the reaction time was 2h (Group B5), the grafting effect of the silane coupling agent on the surface of the PVA adsorption-bridging modified composite particles was the best. The organic layer weight gain measured by TGA was about 3.8%, the characteristic peaks of Si-O-Si and -NH were obvious in the FTIR spectrum, and the particles showed no obvious sedimentation after standing in ethanol for 24h.

[0113] (III) Determination of the optimal combination of modified particles

[0114] Based on the screening results of the PDA adsorption-bridging modification stage and the silane coupling agent grafting modification stage, the A5+B5 condition was determined to be the optimal preparation parameters for the modified composite particles. The modified composite particles prepared under these conditions have the following characteristics:

[0115] Average particle size D50: approximately 110-115 nm

[0116] Particle size distribution index (PDI): 0.12

[0117] Zeta potential: around -32mV

[0118] Weight gain of organic coating: approximately 3.8%

[0119] This modified composite particle exhibits excellent dispersion stability and interfacial bonding ability, making it suitable for the subsequent preparation of modified ethylene propylene rubber composites.

[0120] Based on the characterization results, modified particle combinations that meet the requirements of dispersibility, coating integrity, and thermal stability were selected for subsequent composite material preparation. The optimal modified particle combination selected in this invention is as described in Example 1.

[0121] Experimental Example 2: Performance Testing and Optimization Verification of the Composite Material of the Present Invention

[0122] I. Experimental Methods

[0123] Multi-dimensional performance tests were conducted on the vulcanized composite material samples to verify the optimization effect and screen the optimal process. The test items and methods are as follows:

[0124] Nonlinear conductivity performance testing: Following GB / T 1408.1-2016, the JE curve (current density-electric field intensity curve) of the composite material was measured using a conductivity meter. The nonlinear characteristics were quantified using the nonlinear coefficient formula (Equation I).

[0125] Formula I

[0126] In the formula, J1 and J2 are the current densities under electric field intensities E1 and E2, respectively, and α is the nonlinear coefficient.

[0127] Dielectric property testing: According to GB / T 1409-2006, the relative permittivity and dielectric loss factor of the composite material were tested using a dielectric loss tester. The nonlinearity of the dielectric properties was explained using the multilayer interface equivalent capacitance formula (Equation II).

[0128] Formula II

[0129] In the formula, C + For a unidirectional barrier layer capacitor, C - For the anisotropic barrier layer capacitor, C b For grain boundary layer capacitance, C eq It is a composite equivalent capacitance.

[0130] Corona resistance test: According to GB / T 1408.1-2016, a needle-plate electrode test system was used to simulate the non-uniform electric field environment under the voltage level of vehicle-mounted cables. The corona initiation voltage and ultraviolet photon count rate were recorded by a partial discharge tester to verify the material's suppression effect on corona discharge.

[0131] Environmental adaptability testing: In accordance with GB / T 2423.22-2012, high and low temperature cycling tests and vibration fatigue tests were conducted to evaluate the performance retention rate of the material in harsh vehicle environments and verify the working condition adaptability effect.

[0132] Mechanical property testing: The tensile strength and elongation at break of the composite material are tested in accordance with GB / T 2423.10-2019 to ensure that the material meets the mechanical requirements for use as a stress control tube for cable terminals.

[0133] II. Test Results

[0134] Composite material performance test results under different formulations and process parameters

[0135] (I) Test results corresponding to different combinations of particle modification parameters

[0136] Sample Parameter Description

[0137] Sample S1 (Comparison Sample)

[0138] Composite particles: Without PDA adsorption-bridging and KH550 surface grafting modification, a mixture of nano-ZnO and nano-BaTiO3 in a mass ratio of 4:1 was directly added.

[0139] Combined particle content: 20 phr

[0140] Composite material formulation: Same as Example 1, except that the functional filler is changed to a mixture of nano-ZnO and nano-BaTiO3.

[0141] Mixing process: Same as in Example 1

[0142] Sample S2 (non-optimal modification parameters)

[0143] PDA adsorption-bridging modification parameters: PDA dosage 0.20 g, stirring speed 300 r / min, adsorption time 4 h.

[0144] KH550 modification parameters: 1.0g, 50℃, 2h

[0145] Combined particle content: 20 phr

[0146] Composite material formulation: Same as Example 1, except that the functional filler is replaced with a combination of nanoparticles prepared using the above-mentioned "PDA adsorption-bridging modification parameters" and "KH550 modification parameters".

[0147] Mixing process: Same as in Example 1

[0148] Sample S3 (Optimal solution of the present invention, Example 1)

[0149] PDA adsorption-bridging modification parameters: PDA dosage 0.40 g, stirring speed 500 r / min, adsorption time 6 h.

[0150] KH550 modification parameters: 1.5g, 70℃, 2h

[0151] Combined particle content: 20 phr

[0152] Table 6. Test results of nonlinear conductivity and dielectric properties

[0153]

[0154] Results analysis:

[0155] The composite particles modified by PDA adsorption-bridging and KH550 surface grafting significantly improved the nonlinear conductivity and dielectric constant of the material. Under the modification parameters corresponding to S3, the nonlinear coefficient α was improved most significantly, while the dielectric loss remained at a low level.

[0156] (II) Results of Corona Resistance under Different Mixing Process Parameters

[0157] While keeping the combined particle modification parameters unchanged (using S3 parameters), the third-stage mixing temperature and speed were changed to test the corona resistance performance.

[0158] Mixing Parameter Description

[0159] Sample M1: Third stage 80℃, 40r / min

[0160] Sample M2: Third stage 70℃, 30r / min (Scheme of this invention)

[0161] Sample M3: Third stage 60℃, 20r / min

[0162] Samples M1, M2 and M3 were all prepared in accordance with the method described in Example 1, the only difference being the conditions in the third stage of mixing.

[0163] Corona resistance test results

[0164] Table 7. Results of sample corona initiation voltage (kV) and ultraviolet photon count rate (counts / s)

[0165]

[0166] Results analysis:

[0167] When the mixing temperature in the third stage is 70℃ and the rotation speed is 30r / min, the modified composite particles are most uniformly dispersed in the EPDM matrix, the interfacial bonding effect is the best, the material has the highest corona initiation voltage, and the ultraviolet photon count rate is the lowest, indicating that the partial discharge activity is effectively suppressed.

[0168] (III) Results of Mechanical Properties and Environmental Adaptability Tests

[0169] The composite material prepared using the optimal parameters (S3+M2) (the composite material prepared in Example 1) was subjected to mechanical and environmental adaptability tests, and the results are as follows:

[0170] Table 8. Mechanical property test results

[0171]

[0172] As shown in Table 8, the composite material prepared by this invention has good mechanical properties and environmental adaptability.

[0173] (iv) The influence of different functional fillers on the properties of composite materials

[0174] To verify the synergistic effect of ZnO nanoparticles and BaTiO3 nanoparticles in the system of this invention, composite materials were prepared using PDA-KH550 modified ZnO nanoparticles, PDA-KH550 modified BaTiO3 nanoparticles, and PDA-KH550 composite modified ZnO / BaTiO3 nanoparticles, respectively, while maintaining the same EPDM matrix formulation, total amount of functional fillers, and preparation process (according to Example 1). Their mechanical properties, corona resistance, and dielectric properties were compared and tested, and the results are shown in Table 9. PDA-KH550 modified ZnO nanoparticles and PDA-KH550 modified BaTiO3 nanoparticles were modified according to the methods described in steps S101-S103 of Example 1, with each nanoparticle being 10g.

[0175] Table 9. Comparison of the comprehensive performance of composite materials with different functional filler systems

[0176]

[0177] Table 9 shows that the improvement in dielectric properties and corona initiation voltage of the composite material using modified ZnO nanoparticles alone is limited; the composite material using modified BaTiO3 nanoparticles alone has insufficient nonlinear coefficient and electric field modulation capability. In contrast, the composite material using a combination of modified ZnO / BaTiO3 nanoparticles exhibits superior overall performance in multiple key indicators, including tensile strength, corona initiation voltage, nonlinear coefficient, and dielectric properties. This indicates that ZnO and BaTiO3 in the system of this invention achieve synergistic modulation of electric field distribution and interface properties through the synergistic coupling of nonlinear conductivity and high dielectric properties, thus making the overall performance of the composite material significantly better than that of the single-particle filling system.

[0178] (v) The influence of different functional fillers on the properties of composite materials

[0179] While maintaining the same matrix formulation, total amount of functional fillers, and preparation process as in Example 1, the BaTiO3 nanoparticles in Example 1 were replaced with SiO2 nanoparticles to prepare a comparative composite material. Specifically, SiO2 nanoparticles and ZnO nanoparticles were mixed at a mass ratio of 1:4 (maintaining the same mixing ratio as in Example 1), and modified composite particles were obtained using the same PDA coating and KH550 grafting modification process as in Example 1; subsequently, the composite material was prepared under the same gradient mixing and segmented vulcanization conditions as in Example 1. The obtained samples were tested for mechanical properties, nonlinear conductivity, dielectric properties, and corona resistance using the same methods, and the results are shown in Table 10.

[0180] Table 10. Comparison of properties of composite materials with BaTiO3 replaced by SiO2

[0181]

[0182] As shown in Table 10, under the condition of maintaining the total amount of functional fillers and the same preparation process, replacing BaTiO3 with SiO2 resulted in a significant deterioration in key electrical performance indicators of the composite material, such as relative permittivity, dielectric loss, nonlinear conductivity, and corona initiation voltage. The overall performance was significantly lower than that of the sample in Example 1. This indicates that the BaTiO3-ZnO composite has superior effects compared to other filler composites, proving the irreplaceable nature and significant technical benefits of the present invention.

[0183] As can be seen from the above experiments, the modified ethylene propylene rubber composite material prepared by the present invention has good nonlinear electrical conductivity and dielectric properties, good corona resistance, and excellent mechanical properties, which meets the requirements of high-speed train cables.

[0184] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A modified ethylene propylene rubber composite material, characterized in that: It is prepared from the following raw materials in parts by weight: 100 parts of ethylene propylene rubber, 10-30 parts of polydopamine-coated ZnO and BaTiO3 composite nanoparticles, 20-40 parts of reinforcing agent, 5-15 parts of plasticizer, 1-5 parts of anti-aging agent, 1-5 parts of vulcanizing agent, and 1-5 parts of vulcanization accelerator. The mass ratio of ZnO nanoparticles to BaTiO3 nanoparticles in the polydopamine-coated ZnO and BaTiO3 composite nanoparticles is (3.5-4.5):1; the preparation method of the polydopamine-coated ZnO and BaTiO3 composite nanoparticles includes the following steps: (1) ZnO nanoparticles and BaTiO3 nanoparticles were mixed in a certain mass ratio and then added to Tris-HCl buffer solution and sonicated to prepare a dispersion. (2) Add dopamine hydrochloride to the dispersion and stir until a polydopamine coating layer is formed on the surface of ZnO nanoparticles and BaTiO3 nanoparticles; the mass of the dopamine hydrochloride is 4% of the total mass of ZnO nanoparticles and BaTiO3 nanoparticles; the stirring speed is 500 r / min, the stirring temperature is 20~30℃, and the stirring time is 6h. (3) The nanoparticles obtained in step (2) are washed and dispersed in anhydrous ethanol solution to obtain a suspension. A silane coupling agent is added to the suspension to react and obtain polydopamine-coated ZnO and BaTiO3 composite nanoparticles. The mass of the silane coupling agent is 10-15% of the total mass of nano-ZnO and nano-BaTiO3. The preparation method of the modified ethylene propylene rubber composite material includes the following steps: (a) Weigh each ingredient according to its weight; (b) The raw materials are mixed in a gradient process to obtain a cooked rubber; (c) The calcined rubber is vulcanized to obtain a modified ethylene propylene rubber composite material; In step (b), the gradient mixing is divided into the following three stages: (A-1) Ethylene propylene rubber is added to an internal mixer and mixed to form a uniform rubber matrix; the mixing temperature is 90℃, the rotation speed is 40r / min, and the time is 0.5h. (A-2) Add the anti-aging agent, reinforcing agent and plasticizer to the system in step (A-1) in sequence, and mix them; the mixing temperature is 80℃, the rotation speed is 50r / min, and the time is 0.3h; (A-3) Polydopamine-coated ZnO and BaTiO3 composite nanoparticles are added to the system in step (A-2), followed by the addition of a vulcanizing agent and a vulcanization accelerator, and the mixture is further kneaded to obtain a cured rubber; in step (A-3), the kneading temperature is 70°C, the rotation speed is 30 r / min, and the time is 0.5 h. In step (c), the vulcanization is divided into the following two stages: (B-1) After the granulated rubber is granulated, the first stage of vulcanization is carried out to make the rubber molecular chains initially cross-linked; (B-2) Increase the vulcanization temperature to complete the crosslinking and obtain the composite material.

2. The modified ethylene propylene rubber composite material according to claim 1, characterized in that: It is prepared from the following raw materials in parts by weight: 100 parts of ethylene propylene rubber, 20 parts of polydopamine-coated ZnO and BaTiO3 composite nanoparticles, 30 parts of reinforcing agent, 10 parts of plasticizer, 1.5 parts of anti-aging agent, 2.0 parts of vulcanizing agent, and 1.0 part of vulcanization accelerator.

3. The modified ethylene propylene rubber composite material according to claim 1, characterized in that: In step (1), the mass-to-volume ratio of the total mass of ZnO nanoparticles and BaTiO3 nanoparticles to the volume of Tris-HCl buffer solution is 10g:100~500mL; And / or, in step (3), the concentration of nanoparticles in the suspension is 0.01~0.05 g / mL; And / or, in step (3), the reaction temperature is 70~80℃ and the reaction time is 1~5h.

4. The modified ethylene propylene rubber composite material according to claim 1 or 2, characterized in that: The reinforcing agent is selected from silica; And / or, the plasticizer is selected from one or more combinations of paraffin oil and naphthenic oil; And / or, the anti-aging agent is selected from p-phenylenediamine anti-aging agents; And / or, the vulcanizing agent is selected from peroxide-based vulcanizing agents; And / or, the vulcanization accelerator is selected from triallyl vulcanization accelerators.

5. The modified ethylene propylene rubber composite material according to claim 4, characterized in that: The plasticizer is selected from paraffin oil; And / or, the anti-aging agent is selected from N-isopropyl-N'-phenyl-p-phenylenediamine; And / or, the vulcanizing agent is selected from dicumyl peroxide; And / or, the vulcanization accelerator is selected from triallyl isocyanurate.

6. The method for preparing the modified ethylene propylene rubber composite material according to any one of claims 1 to 5, characterized in that: Includes the following steps: (a) Weigh each ingredient according to its weight; (b) The raw materials are mixed in a gradient process to obtain a cooked rubber; (c) The calcined rubber is vulcanized to obtain a modified ethylene propylene rubber composite material; In step (b), the gradient mixing is divided into the following three stages: (A-1) Ethylene propylene rubber is added to an internal mixer and mixed to form a uniform rubber matrix; the mixing temperature is 90℃, the rotation speed is 40r / min, and the time is 0.5h. (A-2) Add the anti-aging agent, reinforcing agent and plasticizer to the system in step (A-1) in sequence, and mix them; the mixing temperature is 80℃, the rotation speed is 50r / min, and the time is 0.3h; (A-3) Polydopamine-coated ZnO and BaTiO3 composite nanoparticles are added to the system in step (A-2), followed by the addition of a vulcanizing agent and a vulcanization accelerator, and the mixture is further kneaded to obtain a cured rubber; the kneading temperature is 70℃, the rotation speed is 30r / min, and the time is 0.5h. In step (c), the vulcanization is divided into the following two stages: (B-1) After the granulated rubber is granulated, the first stage of vulcanization is carried out to make the rubber molecular chains initially cross-linked; (B-2) Increase the vulcanization temperature to complete the crosslinking and obtain the composite material.

7. The preparation method according to claim 6, characterized in that: In step (B-1), the vulcanization temperature is 150°C, the pressure is 10 MPa, and the time is 10 min; And / or, in step (B-2), the vulcanization temperature is 170°C, the pressure is 10 MPa, and the time is 15 min.

8. The use of the modified ethylene propylene rubber composite material according to any one of claims 1 to 5 in the preparation of stress control tubes for vehicle-mounted high-voltage cable terminals.

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