Nickel-coated graphite composite material for conductive silicone rubber and preparation method of nickel-coated graphite composite material

Abstract

The invention relates to the technical field of nickel-coated graphite materials, in particular to a nickel-coated graphite composite material for conductive silicone rubber and a preparation method of the nickel-coated graphite composite material. The composite material is of a core-shell structure, the outer layer is a polyimide-polyaniline / nickel compound, and the inner core is a graphite / copper compound. Polyimide has good thermal stability and mechanical strength, and polyaniline is introduced to effectively restrain and transfer stress; graphite and copper construct a multi-element conductive path, the layered structure of the graphite has flexibility and lubricity, gaps among copper particles are filled with the graphite, and transmission resistance of electrons among the particles is reduced. The graphite / copper compound provides an efficient internal conductive channel, polyimide-polyaniline / nickel constructs an external conductive network, a multi-layer conductive system is formed, electrons can freely shuttle between the internal channel and the external network, the electron conduction path and efficiency are improved, resistance and energy loss in the electron transmission process are reduced, and the performance of the device is improved. Therefore, the whole material has excellent conductivity.

Description

Technical Field

[0001] The technical field of nickel-coated graphite materials, in particular, relates to a nickel-coated graphite composite material for conductive silicone rubber and a preparation method thereof. Background Art

[0002] Nickel-coated graphite composite material is a conductive filler with good performance in conductive silicone rubber, and is widely used in conductive shielding materials, conductive silicone rubber for 5G base stations, and conductive silicone rubber for new energy vehicles. The nickel-coated graphite composite material has good compatibility with silicone rubber, forms an interconnected conductive network in the silicone rubber matrix, endows it with conductive properties, and can also improve the mechanical properties, wear resistance and thermal conductivity of silicone rubber.

[0003] Nickel-coated graphite composite materials need to have excellent electrical conductivity, stability, dispersibility, high specific surface area, etc. Nickel and graphite itself have certain electrical conductivity. Nickel-coated graphite can combine the advantages of the two, be evenly dispersed in silicone rubber, and build a channel for electron transmission. Chinese patent application with publication number CN 116153586 A discloses a nickel-coated graphite composite conductive powder and a preparation method thereof. In this invention, flaky graphite powder is subjected to alkali washing, roughening, sensitization, activation, nickel coating, and finally reduction and screening to obtain nickel-coated graphite composite conductive powder. The obtained nickel-coated graphite composite conductive powder has advantages such as good coating effect, uniform density, and good electrical conductivity; however, the compatibility between nickel-coated graphite and silicone rubber is limited, and debonding is likely to occur after a period of time, affecting the mechanical properties of the material. At the same time, in order to achieve higher electrical conductivity, a large amount of nickel-coated graphite often needs to be added. This will have a greater impact on the properties of the matrix material, such as making the material too hard, increasing brittleness, and deteriorating processing performance.

[0004] Therefore, it is particularly important to provide a nickel-coated graphite composite material that has good compatibility with silicone rubber, good electrical conductivity, and can enhance the mechanical properties, thermal conductivity and wear resistance of silicone rubber. Summary of the Invention

[0005] This article aims to provide a nickel-coated graphite composite material for conductive silicone rubber and a preparation method thereof. This nickel-coated graphite composite material is an important conductive filler in conductive silicone rubber, which can endow silicone rubber with good electrical conductivity and enhance its mechanical properties and wear resistance at the same time.

[0006] To achieve the above object, the present invention provides a nickel-coated graphite composite material for conductive silicone rubber. This nickel-coated graphite composite material is a core-shell composite material, including an outer layer and an inner core; the outer layer is a nickel layer, and the inner core is a graphite / copper composite deposited with a conductive polymer; the structural formula of the conductive polymer is as follows:

[0007] ,

[0008] Among them, n takes an integer between 1 and 10, and m takes an integer between 1 and 10.

[0009] The present invention also provides a preparation method of a nickel-coated graphite composite material for conductive silicone rubber, including:

[0010] Step S1: Mix graphite powder with an acid and react to obtain graphite powder with surface acid treatment;

[0011] Step S2: Add the graphite powder with surface acid treatment to a sensitizing solution, wash it after treatment, and dry it to obtain sensitized graphite powder;

[0012] Step S3: Add the sensitized graphite powder to an activation solution, activate, wash, and dry it to obtain activated graphite powder;

[0013] Step S4: Mix the activated graphite powder and copper powder and add them to a ball mill for premixing to obtain a graphite / copper mixture. Add grinding balls, absolute ethanol, and a dispersant, grind and sinter to obtain a graphite / copper composite, and place it in the reaction chamber of a chemical vapor deposition device;

[0014] Step S5: Pass aniline gas, phthalic anhydride gas, and 4,4'-diaminodiphenyl ether gas into the reaction chamber described in Step S4, pass in a carrier gas, and react to obtain a polyimide-polyaniline copolymer;

[0015] Step S6: Adjust the system pressure and lower the temperature to deposit the polyimide-polyaniline composite on the surface of the graphite / copper composite to obtain composite graphite powder;

[0016] Step S7: Add water to a reaction kettle, preheat, continue to add a complexing agent, a stabilizer, and a nickel sulfate solution, adjust the pH value to be alkaline, add the composite graphite powder and a reducing agent, stir to obtain a crude product of the nickel-coated graphite composite material, and perform annealing treatment on it, wash it to neutrality, and dry it to obtain the nickel-coated graphite composite material.

[0017] Preferably, in the step S1, the acid is any one or more of nitric acid and sulfuric acid.

[0018] Preferably, in the step S1, the mass ratio of the graphite powder to the acid is 1:(5-10).

[0019] Preferably, in the step S1, the reaction temperature is 50-80°C, and the reaction time is 1-3 h.

[0020] Preferably, in the step S2, the sensitizing solution is a solution prepared with a mass ratio of stannous chloride, hydrochloric acid, and water of 1:(2-3):(5-10);

[0021] Preferably, in the step S2, the mass ratio of the surface-treated graphite powder to the sensitizing solution is 1:(2-3).

[0022] Preferably, in the step S2, the processing time is 10 to 30 min.

[0023] Preferably, in the step S2, the washing solvent is deionized water.

[0024] Preferably, in the step S2, the drying temperature is 40 to 60 °C, and the drying time is 3 to 6 h.

[0025] Preferably, in the step S3, the activation solution is a solution prepared by mixing palladium chloride, water, and hydrochloric acid in a mass ratio of 1:(2 - 3):(0.05 - 0.15).

[0026] Preferably, in the step S3, the mass ratio of the sensitized graphite powder to the activation solution is 1:(2 - 3).

[0027] Preferably, in the step S3, the washing solvent is deionized water.

[0028] Preferably, in the step S3, the activation time is 10 to 20 min.

[0029] Preferably, in the step S3, the drying temperature is 40 to 60 °C, and the drying time is 3 to 6 h.

[0030] Preferably, in the step S4, the purity of the copper powder is 99%.

[0031] Preferably, in the step S4, the dispersant is any one or more of sodium oleate, sodium pyrophosphate, and sodium dodecylbenzenesulfonate.

[0032] Preferably, in the step S4, the mass ratio of the activated graphite powder, copper powder, dispersant, and absolute ethanol is 1:(0.5 - 1):(0.1 - 0.2):(3 - 4).

[0033] Preferably, in the step S4, the mass ratio of the graphite / copper mixture to the grinding balls is 1:(10 - 20).

[0034] Preferably, in the step S4, the grinding time is 2 to 4 h, and the rotation speed is 400 to 600 r / min.

[0035] Preferably, in the step S4, the sintering temperature is 800 to 1000 °C, the heating rate is 5 to 10 °C / min, the pressure is 10 -4 ~10 -3 Pa, and the time is 2 to 4 h.

[0036] Preferably, in the step S5, the carrier gas is any one or more of argon, helium, nitrogen, and hydrogen.

[0037] Preferably, in the step S5, the flow rate ratio of aniline gas, phthalic anhydride gas, 4,4'-diaminodiphenyl ether gas, and the carrier gas is 1: (1~2): (1~1.2): (10~40).

[0038] Preferably, in the step S5, the reaction temperature is 300~600 °C, the reaction time is 2~3 h, and the system pressure of the reaction is 10 -2 ~10 2 Pa.

[0039] Preferably, in the step S6, the flow rate ratio of the polyaniline precursor gas, the polyimide precursor gas, and the carrier gas is 1: (1~2): (10~40).

[0040] Preferably, in the step S6, the system pressure is adjusted to 10 -5 ~10 -3 Pa.

[0041] Preferably, in the step S6, the temperature is reduced to 100~150 °C.

[0042] Preferably, in the step S6, the deposition time is 1~3 h.

[0043] Preferably, in the step S7, the preheating temperature is 80~90 °C.

[0044] Preferably, in the step S7, the complexing agent is any one or more of sodium tartrate, sodium citrate, sodium ethylene diamine tetra (methylene phosphonate), and hydroxyethane diphosphonic acid sodium.

[0045] Preferably, in the step S7, the stabilizer is any one or more of sodium thiosulfate, thioglycolic acid, and butynediol.

[0046] Preferably, in the step S7, the reducing agent is any one or more of sodium hypophosphite, hydrazine hydrate, sodium borohydride, citric acid, and oxalic acid.

[0047] Preferably, in the step S7, the mass ratio of water, complexing agent, stabilizer, nickel sulfate solution, reducing agent, and composite graphite powder is 1: (0.01~0.02): (0.02~0.04): (0.15~0.3): (0.0005~0.001): (0.05~0.1).

[0048] Preferably, in step S7, the temperature of the stirring is 90-95 °C, the speed of the stirring is 200-400 r / min, and the time of the stirring is 1-3 h.

[0049] Preferably, in step S7, the temperature of the annealing treatment is 300-500 °C, the time is 1-3 h, and the protective gas is an inert gas, such as any one or more of helium, argon, nitrogen, etc.

[0050] Preferably, in step S7, the washing solvent is deionized water, the drying temperature is 40-60 °C, and the drying time is 8-12 h.

[0051] A nickel-coated graphite composite material for conductive silicone rubber provided by the present invention is applied to the preparation of conductive silicone rubber. The conductive silicone rubber is obtained by mixing silicone rubber raw rubber and the nickel-coated graphite composite material; the conductive filler is obtained by the above preparation method.

[0052] Preferably, the silicone rubber raw rubber is any one or more of dimethyl silicone rubber raw rubber, methyl vinyl silicone rubber raw rubber, and methyl phenyl silicone rubber raw rubber.

[0053] Preferably, the mixing temperature is 50-100 °C, and the time is 20-60 min.

[0054] Preferably, the mass ratio of the silicone rubber raw rubber to the conductive filler is 1:(0.2-0.5).

[0055] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0056] (1) The present invention uses polyimide-polyaniline / nickel composite as the outer shell of the coated graphite composite material. Polyaniline is a conductive polymer material. When combined with polyimide, it can introduce conductive channels into the insulating polyimide matrix. Polyimide itself has excellent mechanical properties and wear resistance. The addition of polyaniline does not affect the performance of polyimide. The combination of the two can improve the flexibility while maintaining high strength, enabling it to adapt to different application scenarios. Nickel has a large number of freely movable electrons, which can build an efficient conductive network with the polyimide-polyaniline polymer, providing a low-resistance channel for electron transmission and promoting the migration of carriers in the polyimide-polyaniline polymer. The interface formed between nickel and the polyimide-polyaniline polymer expands the electron transmission path, increases the transmission probability of carriers, and improves the conductivity of the material.

[0057] (2) The present invention uses a polyimide-polyaniline / nickel composite to coat a graphite / copper composite. Graphite has a unique layered structure with a large π bond between carbon atoms within the layer. Copper is a metal with excellent electrical conductivity, and there are a large number of freely movable electrons within it. When copper and graphite are combined, the interfacial bonding between the two substances is tight, and the electrons inside copper can move freely within the graphite layer, forming an efficient conductive channel. The efficient conductive network constructed by the polyimide-polyaniline / nickel composite combines with the conductive channel formed by copper and graphite. There is a certain interfacial interaction between the core and the shell, and at the interface, electrons can achieve cross-interface transmission through tunneling effect and other means, further optimizing the electrical conductivity, reducing the hindrance during the electron transmission process, and making the electrical conductivity of the entire filler more excellent and stable. Description of the Drawings

[0058] Figure 1 It is a preparation flow chart of a nickel-coated graphite composite material for conductive silicone rubber.

[0059] Figure 2 It is a scanning electron micrograph of the nickel-coated graphite composite material for conductive silicone rubber prepared in Example 3.

[0060] Figure 3 It is a schematic diagram of the synthesis route of the polyimide-polyaniline copolymer. Specific Embodiments

[0061] The following examples are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0062] The main compounds used in the examples and comparative examples are all commercially available products without any further purification treatment.

[0063] Example 1

[0064] As Figure 1 shown, a nickel-coated graphite composite material for conductive silicone rubber, the preparation method includes the following steps:

[0065] Step S1: Mix 5 g of graphite powder with 25 g of nitric acid and react at 50 °C for 3 h to obtain surface acid-treated graphite powder.

[0066] Step S2: Dissolve 5 g of stannous chloride in 10 g of hydrochloric acid, add 25 g of water to obtain a sensitizing solution; add 5 g of surface acid-treated graphite powder to 10 g of the sensitizing solution, after treatment for 30 min, wash with deionized water and dry at 40 °C for 6 h to obtain sensitized graphite powder.

[0067] Step S3: Dissolve 5 g of palladium chloride in 10 g of water, add 0.25 g of hydrochloric acid to obtain an activation solution; add 5 g of sensitized graphite powder to 10 g of the activation solution, activate for 20 min, wash with deionized water, and dry at 40 °C for 6 h to obtain activated graphite powder.

[0068] Step S4: Mix 5 g of activated graphite powder and 2.5 g of copper powder with a purity of 99% and add them to a ball mill for premixing to obtain a graphite / copper mixture. Add 75 g of grinding balls, 15 g of absolute ethanol, and 0.5 g of sodium oleate, and grind at a rotation speed of 400 r / min for 4 h. Under 10 -3 Pa, heat up to 800 °C at a rate of 5 °C / min and sinter for 4 h to obtain a graphite / copper composite, and place it in the reaction chamber of a chemical vapor deposition device.

[0069] Step S5: Pass aniline gas into the reaction chamber at a flow rate of 5 sccm, phthalic anhydride gas into the reaction chamber at a flow rate of 5 sccm, 4,4'-diaminodiphenyl ether gas into the reaction chamber at a flow rate of 5 sccm, and argon gas into the reaction chamber at a flow rate of 50 sccm. React at 300 °C and 10 -2 Pa for 3 h to obtain a polyimide-polyaniline copolymer, as Figure 3 shown.

[0070] Step S6: Adjust the system pressure to 10 -3 Pa, lower the temperature to 100 °C, and deposit the polyimide-polyaniline composite on the surface of the graphite / copper composite for 3 h to obtain composite graphite powder.

[0071] Add 100 g of water to the reaction kettle, preheat the reaction kettle to 80 °C, add 1 g of sodium tartrate, 2 g of sodium thiosulfate, 15 g of nickel sulfate solution, adjust the pH value to 9, add 5 g of composite graphite powder and 0.05 g of sodium hypophosphite, stir at a rotation speed of 200 r / min for 3 h at 90 °C to obtain a crude product of nickel-coated graphite composite material. The crude product is annealed at 300 °C for 3 h, washed to neutral, and dried at 40 °C for 12 h to obtain a nickel-coated graphite composite material.

[0072] Example 2

[0073] As Figure 1 shown, a preparation method of a nickel-coated graphite composite material for conductive silicone rubber includes the following steps:

[0074] Step S1: Mix 5 g of graphite powder with 35 g of nitric acid and react at 65 °C for 2 h to obtain surface acid-treated graphite powder.

[0075] Step S2: Dissolve 5 g of stannous chloride in 15 g of hydrochloric acid, add 35 g of water to obtain a sensitizing solution; add 5 g of surface acid-treated graphite powder to 15 g of the sensitizing solution, treat for 10 min, wash with deionized water, and dry at 60 °C for 3 h to obtain sensitized graphite powder.

[0076] Step S3: Dissolve 5 g of palladium chloride in 15 g of water, add 0.5 g of hydrochloric acid to obtain an activating solution; add 5 g of sensitized graphite powder to 15 g of the activating solution, activate for 10 min, wash with deionized water, and dry at 50 °C for 4 h to obtain activated graphite powder.

[0077] Step S4: Mix 5 g of activated graphite powder and 3.5 g of copper powder with a purity of 99% and add them to a ball mill for premixing to obtain a graphite / copper mixture. Add 125 g of grinding balls, 20 g of absolute ethanol, and 1 g of sodium pyrophosphate, grind at a speed of 500 r / min for 3 h, and under 10 -4 Pa, heat up to 900 °C at a rate of 7 °C / min, sinter for 3 h to obtain a graphite / copper composite, and place it in the reaction chamber of a chemical vapor deposition device.

[0078] Step S5: Pass aniline gas into the reaction chamber at a flow rate of 5 sccm, phthalic anhydride gas into the reaction chamber at a flow rate of 10 sccm, 4,4'-diaminodiphenyl ether gas into the reaction chamber at a flow rate of 6 sccm, and helium gas into the reaction chamber at a flow rate of 125 sccm. React at 450 °C and 10 Pa for 2 h to obtain a polyimide-polyaniline copolymer, as Figure 3 shown.

[0079] Step S6: Adjust the system pressure to 10 -4 Pa, lower the temperature to 120 °C, and deposit the polyimide-polyaniline composite on the surface of the graphite / copper composite for 2 h to obtain composite graphite powder.

[0080] Step S7: Add 100 g of water to the reaction kettle, preheat the reaction kettle to 90 °C, add 2 g of sodium citrate, 3 g of thioglycolic acid, 20 g of nickel sulfate solution, adjust the pH value to 10, add 7.5 g of composite graphite powder and 0.075 g of hydrazine hydrate, stir at a speed of 300 r / min at 95 °C for 2 h to obtain a crude product of nickel-coated graphite composite material. The crude product is annealed at 400 °C for 2 h, washed to neutral, and dried at 50 °C for 10 h to obtain a nickel-coated graphite composite material.

[0081] Example 3

[0082] As Figure 1 shown, a nickel-coated graphite composite material for conductive silicone rubber, the preparation method includes the following steps:

[0083] Step S1: Mix 5 g of graphite powder with 50 g of nitric acid and react at 80 °C for 1 h to obtain surface acid-treated graphite powder.

[0084] Step S2: Dissolve 5 g of stannous chloride in 15 g of hydrochloric acid, add 35 g of water to obtain a sensitizing solution; add 5 g of surface acid-treated graphite powder to 15 g of the sensitizing solution, after treatment for 20 min, wash with deionized water and dry at 50 °C for 5 h to obtain sensitized graphite powder.

[0085] Step S3: Dissolve 5 g of palladium chloride in 15 g of water, add 0.75 g of hydrochloric acid to obtain an activating solution; add 5 g of sensitized graphite powder to 15 g of the activating solution, activate for 10 min, wash with deionized water and dry at 60 °C for 3 h to obtain activated graphite powder.

[0086] Step S4: Mix 5 g of activated graphite powder and 3.5 g of copper powder with a purity of 99% and add them to a ball mill for premixing to obtain a graphite / copper mixture. Add 125 g of grinding balls, 20 g of absolute ethanol and 1 g of sodium dodecylbenzenesulfonate, grind at a speed of 500 r / min for 3 h, and under 10 -4 Pa, heat up to 1000 °C at a rate of 10 °C / min and sinter for 2 h to obtain a graphite / copper composite, and place it in the reaction chamber of a chemical vapor deposition device.

[0087] Step S5: Introduce aniline gas into the reaction chamber at a flow rate of 5 sccm, phthalic anhydride gas at a flow rate of 10 sccm, 4,4'-diaminodiphenyl ether gas at a flow rate of 6 sccm, and nitrogen gas at a flow rate of 200 sccm into the reaction chamber. React at 600 °C and 102 Pa for 2 h to obtain a polyimide-polyaniline copolymer, as Figure 3 shown.

[0088] Step S6: Adjust the system pressure to 10 -5 Pa, lower the temperature to 150 °C, and deposit the polyimide-polyaniline composite on the surface of the graphite / copper composite for 1 h to obtain composite graphite powder.

[0089] Step S7: Add 100 g to the reaction kettle, preheat the reaction kettle to 90 °C, add 2 g of sodium citrate, 4 g of butynediol, 30 g of nickel sulfate solution, adjust the pH value to 10, add 10 g of composite graphite powder and 0.1 g of sodium borohydride, stir at a speed of 400 r / min at 95 °C for 1 h to obtain a crude product of nickel-coated graphite composite material. The crude product is annealed at 500 °C for 1 h, washed to neutral, and dried at 60 °C for 8 h to obtain a nickel-coated graphite composite material.

[0090] Comparative Example 1

[0091] A preparation method of nickel-coated graphite composite material for conductive silicone rubber, which is different from Example 3 in that copper powder is not added in step S1.

[0092] Comparative Example 2

[0093] A preparation method of nickel-coated graphite composite material for conductive silicone rubber, which is different from Example 3 in that aniline gas is not introduced in step S2.

[0094] Comparative Example 3

[0095] A preparation method of nickel-coated graphite composite material for conductive silicone rubber, which is different from Example 3 in that phthalic anhydride gas and 4,4'-diaminodiphenyl ether gas are not added in step S2.

[0096] Scanning electron microscope: The nickel-coated graphite composite material for conductive silicone rubber prepared in Example 3 was photographed with a scanning electron microscope to observe its microscopic morphology. As Figure 2 shown, the sample prepared in Example 3 presented irregular blocks with different sizes, and the overall distribution was relatively uniform; the surface of the blocks was relatively rough, and protrusions generated by the gas-phase deposition of conductive polymers could be observed on the surface; the attachments on the surface of the blocks were evenly distributed, which proved that the method of Example 3 could evenly coat the material with nickel and obtain a composite material with a uniform and stable nickel layer thickness.

[0097] Performance test: The tensile strength (GB / T528), elongation at break (GB / T 528), tear strength (GB / T 529), volume resistivity (GB / T 3048.3), abrasion resistance (GB / T 9867), and high-temperature resistance (aging at 350 °C for 5 h) performance (GB / T 7141) of the conductive silicone rubbers prepared in Examples 1-3 and Comparative Examples 1-3 were tested.

[0098] Table 1 Mechanical property test data of conductive silicone rubber

[0099]

[0100] According to the data in Table 1, the tensile strength of the conductive silicone rubber obtained by adding the nickel-coated graphite composites prepared in Examples 1 to 3 is higher than 7 MPa, while the tensile strength of the conductive silicone rubber obtained by adding the nickel-coated graphite prepared in Comparative Examples 1 to 3 is less than 7 MPa. The conductive silicone rubber obtained in Examples 1 to 3 can withstand greater external forces, with higher durability and safety. The elongation at break of the conductive silicone rubber obtained in Examples 1 to 3 is above 650%, while that of the silicone rubber obtained in Comparative Examples 1 to 3 is below 650%. The silicone rubber obtained in Examples 1 to 3 shows ductility and toughness, with good impact resistance and a higher service life. The tear strength of the conductive silicone rubber obtained in Examples 1 to 3 is above 40 N / mm, while that of the conductive silicone rubber obtained in Comparative Examples 1 to 3 is below 40 N / mm. The conductive silicone rubber obtained in Examples 1 to 3 has a stronger resistance when subjected to tearing force, and its mechanical properties are more superior. Experiments have proved that adding the nickel-coated graphite composites prepared by the methods of Examples 1 to 3 to silicone rubber can enhance the mechanical properties of the silicone rubber. The mechanical properties of Comparative Example 3 are relatively the worst, and the main reason is that the outer shell part of the nickel-coated graphite composite prepared in Comparative Example 3 lacks polyimide, resulting in a low polymer crosslinking density and thus poor mechanical properties.

[0101] Table 2 Test Data of Electrical Properties of Conductive Silicone Rubber

[0102]

[0103] According to the data in Table 2, for the conductive silicone rubber obtained by adding the nickel-coated graphite composites prepared in Examples 1 to 3, both the volume resistivity and the surface resistivity are lower than those of the conductive silicone rubber obtained by adding the nickel-coated graphite composites prepared in Comparative Examples 1 to 3. The main reason is that copper powder is added to the core of the composites prepared in Examples 1 to 3, while copper powder is not added in Comparative Example 1. There are a large number of freely movable electrons inside copper, which can improve the conductivity of the composite. In contrast, the outer shell part of the nickel-coated graphite composite prepared in Comparative Example 2 lacks the synergistic conductivity of polyaniline and nickel, and no conductive network with a larger specific surface area is formed, resulting in a reduction in the overall conductivity of the conductive silicone rubber.

[0104] Table 3 Test Data of Wear Resistance of Conductive Silicone Rubber

[0105]

[0106] According to the data in Table 3, the conductive silicone rubbers obtained by adding the nickel-coated graphite composite materials prepared in Examples 1 to 3 can withstand friction for more than 300 h, showing good wear resistance. The wear resistance of the conductive silicone rubber obtained by adding the nickel-coated graphite composite materials prepared in Comparative Example 1 is slightly lower than that of Examples 1 to 3. The friction time that the conductive silicone rubbers obtained by adding the nickel-coated graphite composite materials prepared in Comparative Examples 2 to 3 can withstand is less than 250 h, which is poorer than that of Examples 1 to 3. The main reason is that the shell materials of the nickel-coated graphite composite materials prepared in Comparative Examples 2 and 3 lack polyaniline and polyimide, respectively, which leads to a decrease in the overall crosslinking density of the shell composite.

[0107] Table 4 Conductive silicone rubber aging test data at 350℃ for 5 h

[0108]

[0109] As shown in Table 4, the tensile strength, tear strength, and elongation at break of the silicone rubber obtained by adding the nickel-coated graphite composite materials prepared in Examples 1-3 decreased after aging at 350°C for 5 hours, but remained at relatively high levels compared to Comparative Examples 1-3. The volume and surface resistivities of the conductive silicone rubber obtained in Examples 1-3 also increased after aging, but the increase was significantly less than that of the conductive silicone rubber obtained in Comparative Examples 1-3. This is primarily due to the superior structure of the nickel-coated graphite composite materials prepared in Examples 1-3, which imparted improved conductivity, mechanical properties, wear resistance, and heat resistance to the conductive silicone rubber.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A nickel-coated graphite composite material for conductive silicone rubber, characterized in that, The nickel-coated graphite composite material is a core-shell composite material, including an outer layer and an inner core; the outer layer is a nickel layer, and the inner core is a graphite / copper composite deposited with a conductive polymer; the structural formula of the conductive polymer is as follows: ， Among them, n takes an integer between 1 and 10, and m takes an integer between 1 and 10.

2. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 1, characterized in that, Including: Step S1: Mix graphite powder with an acid, and react to obtain graphite powder with surface acid treatment; Step S2: Add the graphite powder with surface acid treatment to a sensitizing solution, wash it after treatment, and dry it to obtain sensitized graphite powder; Step S3: Add the sensitized graphite powder to an activating solution, activate, wash, and dry it to obtain activated graphite powder; Step S4: Mix the activated graphite powder and copper powder and add them to a ball mill for premixing to obtain a graphite / copper mixture. Add grinding balls, absolute ethanol, and a dispersant, grind and sinter to obtain a graphite / copper composite, and place it in the reaction chamber of a chemical vapor deposition device; Step S5: Pass aniline gas, phthalic anhydride gas, and 4,4'-diaminodiphenyl ether gas into the reaction chamber described in Step S4, pass in a carrier gas, and react to obtain a polyimide-polyaniline copolymer; Step S6: Adjust the system pressure and lower the temperature to deposit the polyimide-polyaniline composite on the surface of the graphite / copper composite to obtain composite graphite powder; Step S7: Add water to a reaction kettle, preheat, continue to add a complexing agent, a stabilizer, and a nickel sulfate solution, adjust the pH value to be alkaline, add the composite graphite powder and a reducing agent, stir to obtain a crude product of the nickel-coated graphite composite material, and perform annealing treatment on it, wash it to neutrality, and dry it to obtain the nickel-coated graphite composite material.

3. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, wherein, In the said Step S1, the acid is any one or more of nitric acid and sulfuric acid; the mass ratio of the graphite powder to the acid is 1:(5-10); the reaction temperature is 50-80 °C, and the reaction time is 1-3 h; in the said Step S2, the sensitizing solution is a solution prepared by stannous chloride, hydrochloric acid, and water according to a mass ratio of 1:(2-3):(5-10); the mass ratio of the surface-treated graphite powder to the sensitizing solution is 1:(2-3); the treatment time is 10-30 min; the washing solvent is deionized water; the drying temperature is 40-60 °C, and the drying time is 3-6 h.

4. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, characterized in that, In the said Step S3, the activating solution is a solution prepared by palladium chloride, water, and hydrochloric acid according to a mass ratio of 1:(2-3):(0.05-0.15); the mass ratio of the sensitized graphite powder to the activating solution is 1:(2-3); the washing solvent is deionized water; the activation time is 10-20 min; the drying temperature is 40-60 °C, and the drying time is 3-6 h.

5. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, characterized in that, In the step S4, the purity of the copper powder is 99%; the dispersant is any one or more of sodium oleate, sodium pyrophosphate, and sodium dodecylbenzenesulfonate; the mass ratio of the activated graphite powder, copper powder, dispersant, and absolute ethanol is 1: (0.5 - 1): (0.1 - 0.2): (3 - 4); the mass ratio of the graphite / copper mixture to the grinding balls is 1: (10 - 20); the grinding time is 2 - 4 h, and the rotation speed is 400 - 600 r / min; the sintering temperature is 800 - 1000 °C, the heating rate is 5 - 10 °C / min, the pressure is 10 -4 ~10 -3 Pa, and the time is 2 - 4 h.

6. The preparation method of the nickel-coated graphite composite material for conductive silicone rubber according to claim 2, characterized in that, In the step S5, the carrier gas is any one or more of argon, helium, nitrogen, and hydrogen; the flow rate ratio of aniline gas, phthalic anhydride gas, 4,4'-diaminodiphenyl ether gas, and the carrier gas is 1:(1~2):(1~1.2):(10~40); the reaction temperature is 300~600 °C, the reaction time is 2~3 h, and the system pressure of the reaction is 10 -2 ~10 2 Pa.

7. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, characterized in that, In the step S6, the flow rate ratio of the polyaniline precursor gas, the polyimide precursor gas and the carrier gas is 1:(1-2):(10-40); the reaction temperature is 250-500 °C, the reaction time is 1-3 h, and the reaction system pressure is 10 -2 ~10 2 Pa; adjusting the system pressure to 10 -5 ~10 -3 Pa; reducing the temperature to 100-150 °C; the deposition time is 1-3 h.

8. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, wherein, In the step S7, the preheating temperature is 80 to 90 °C; the complexing agent is any one or more of sodium tartrate, sodium citrate, sodium ethylene diamine tetra(methylene phosphonate), and hydroxyethane diphosphonic acid sodium; the stabilizer is any one or more of sodium thiosulfate, thioglycolic acid, and butynediol; the reducing agent is any one or more of sodium hypophosphite, hydrazine hydrate, sodium borohydride, citric acid, and oxalic acid; the mass ratio of water, complexing agent, stabilizer, nickel sulfate solution, reducing agent, and composite graphite powder is 1:(0.01 to 0.02):(0.02 to 0.04):(0.15 to 0.3):(0.0005 to 0.001):(0.05 to 0.1).

9. The preparation method of a nickel-coated graphite composite material for conductive silicone rubber according to claim 2, wherein, In the step S7, the temperature of stirring is 90 to 95 °C, the stirring speed is 200 to 400 r / min, and the stirring time is 1 to 3 h; the annealing treatment temperature is 300 to 500 °C, the time is 1 to 3 h, and the protective gas is an inert gas, such as any one or more of helium, argon, and nitrogen; the washing solvent is deionized water, the drying temperature is 40 to 60 °C, and the drying time is 8 to 12 h.

10. A conductive silicone rubber, characterized in that, The conductive silicone rubber is obtained by mixing silicone rubber raw rubber and conductive filler; the conductive filler is obtained by using the preparation method described in any one of claims 2 to 9; the silicone rubber raw rubber is any one or more of dimethyl silicone rubber raw rubber, methyl vinyl silicone rubber raw rubber, and methyl phenyl silicone rubber raw rubber; the mixing temperature is 50 to 100 °C, and the time is 20 to 60 min; the mass ratio of the silicone rubber raw rubber and the conductive filler is 1:(0.2 to 0.5).

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