A heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound and its preparation method

Abstract

The present invention discloses a heat-resistant and thermally conductive nano-silver wire reinforced silicone rubber compound and a preparation method thereof. First, polyvinylpyrrolidone is introduced into the interlayer of montmorillonite through the action of hydroxyl groups on the surface of montmorillonite. Then, silver ions are fixed on the polyvinylpyrrolidone-montmorillonite composite material through the cation exchange between silver ions and montmorillonite and the chelation with the polyvinylpyrrolidone chain. Then, the silver ions are in-situ reduced to nano-silver wires embedded in the interlayer of montmorillonite through ethylene glycol. Finally, the nano-silver wire-montmorillonite composite material is mixed with silicone rubber to obtain the target product. In the rubber compound provided by the present invention, the nano-silver wires grow in-situ between the layers of montmorillonite, a three-dimensional thermal conduction network is constructed through the interlayer confinement effect of montmorillonite, the interfacial compatibility between the filler and the silicone rubber is improved, and the heat resistance of the silicone rubber is enhanced. The heat-resistant and thermally conductive silicone rubber compound of the present invention can be used for designing and preparing thermal interface materials.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, and particularly relates to a heat-conducting silicone rubber compound and a preparation method thereof. Background Art

[0002] The heat accumulation of modern electronic devices has become increasingly serious. Operating at too high a temperature will cause irreversible damage to electronic devices. Therefore, high-performance thermal interface materials (TIMs) are required to solve the heat accumulation problem. Silicone rubber has excellent properties such as high heat resistance, good electrical insulation, easy processability, low cost, and good chemical stability, and is a widely used matrix for thermal interface materials. However, the thermal conductivity of ordinary silicone rubber is only about 0.1-0.2 W / (m·K), which cannot meet the heat dissipation requirements of electronic components under high power density. Therefore, in order to improve the thermal conductivity of silicone rubber, heat-conducting fillers are usually added. Currently, commonly used heat-conducting fillers mainly include carbon nanotubes, boron nitride, aluminum nitride, aluminum oxide, silicon carbide, etc. In the case of random distribution of heat-conducting fillers, a high content of heat-conducting fillers is required to obtain a high thermal conductivity, which will also seriously damage the mechanical properties of silicone rubber.

[0003] Patent CN108102381B "A high heat-conducting silicone rubber composite material and a preparation method thereof" mixes graphene with silver powder having Ag / AgI nanoclusters formed on the surface, and then adds the mixture to the precursor of the silicone rubber matrix to prepare a high heat-conducting silicone rubber composite material. Although this method has achieved good heat-conducting effects, the filling amount of silver powder is very high, and the mechanical properties of the silicone rubber composite material are unknown. Patent CN109777113B "An insulating and heat-conducting silicone rubber composite material and a preparation method thereof" adds hexagonal boron nitride modified with nano silver to silicone rubber to prepare an insulating and heat-conducting silicone rubber composite material. However, the addition amount of boron nitride in this method is very high, and the thermal conductivity of the prepared silicone rubber composite material is not significantly improved compared with boron nitride heat-conducting silicone rubber. Patent CN109943075A "A preparation method of a magnetically oriented graphene heat-conducting silicone rubber composite material" uses a chemical co-precipitation method to prepare magnetic iron oxide nanoparticles, adsorbs them onto the surface of graphene through electrostatic interaction, and then adds the magnetically functionalized graphene filler to silicone rubber to prepare a magnetically oriented graphene heat-conducting silicone rubber composite material. Although the thermal conductivity of the above-prepared heat-conducting silicone rubber reaches 0.59 W / (m·K), the ultra-high thermal conductivity of graphene itself cannot be reflected. Therefore, it is of great significance to develop heat-conducting silicone rubber with excellent properties and promote its wide application in the electronic and electrical industries by preparing high heat-conducting silicone rubber at low filler load, meeting its required mechanical properties and heat resistance, and having a simple production process. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound and a preparation method thereof.

[0005] To achieve the purpose, the present invention adopts the following technical solutions:

[0006] A preparation method of a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound provided by the present invention is characterized in that: first, polyvinylpyrrolidone is introduced into the interlayer of montmorillonite through the action of hydroxyl groups on the surface of montmorillonite, and then silver ions are fixed on the polyvinylpyrrolidone-montmorillonite composite material through cation exchange of silver ions with montmorillonite and chelation with the polyvinylpyrrolidone chain. Then, ethylene glycol is used to in-situ reduce silver ions to nano silver wires embedded in the interlayer of montmorillonite to obtain a nano silver wire-montmorillonite composite material; finally, the nano silver wire-montmorillonite composite material is mixed with silicone rubber under stirring, and after grinding and ultrasonic dispersion, a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound is obtained. Nano silver wires have very excellent thermal conductivity, and the three-dimensional thermal conduction network formed with montmorillonite can play a very good thermal conduction effect in silicone rubber, and at the same time can avoid local overheating of silicone rubber, thereby slowing down the degradation rate of silicone rubber and improving the heat resistance stability of silicone rubber.

[0007] The preparation method of the present invention specifically includes the following steps:

[0008] (1) Montmorillonite is added to deionized water and magnetically stirred until evenly dispersed to obtain a montmorillonite aqueous solution; polyvinylpyrrolidone is dissolved in acetic acid to obtain a polyvinylpyrrolidone solution; the polyvinylpyrrolidone solution is mixed with the montmorillonite aqueous solution and heated and stirred to obtain a polyvinylpyrrolidone-montmorillonite composite material solution as a template guiding agent;

[0009] (2) Silver nitrate is dissolved in the first portion of ethylene glycol to obtain a silver nitrate solution; another portion of ethylene glycol is taken in a three-necked flask and heated to 120-180 °C, and copper chloride is added and kept at a constant temperature for 5-30 min; the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite composite material solution are simultaneously injected into the three-necked flask at a rate of 5-20 mL / min and continue to react at a constant temperature for 0.5-3 h; after the reaction is completed, it is cooled to room temperature, and the obtained product is centrifuged and purified successively with acetone, deionized water, and absolute ethanol to obtain a nano silver wire-montmorillonite composite material;

[0010] (3) Preparation of silicone rubber compound

[0011] The nano silver wire-montmorillonite composite material in step (2) is added to silicone rubber, and after stirring, three-roll grinding and / or ultrasonic treatment, a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound is obtained.

[0012] Preferably, the montmorillonite is one or any combination of natural montmorillonite, lithium montmorillonite, sodium montmorillonite, magnesium montmorillonite and calcium montmorillonite. The molecular weight of the polyvinylpyrrolidone is 30,000 to 1,300,000. The silicone rubber is one or any combination of methyl, vinyl, phenyl, fluoro and nitrile silicone rubbers.

[0013] Preferably, in step (1), the mass ratio of the montmorillonite to the polyvinylpyrrolidone is 1:0.5 to 2.

[0014] Preferably, in step (1), the heating and stirring are carried out at 40 to 80 °C for 6 to 18 h.

[0015] Preferably: in step (2), the concentration of the silver nitrate solution is 0.1 to 0.5 g / 20 mL, and the dosage ratio of the silver nitrate solution, the second portion of ethylene glycol to copper chloride is 20 mL:20 to 200 mL:1.0×10 -4 ~1.0×10 -3 g; in step (2), the mass ratio of silver nitrate to the montmorillonite in step (1) is 0.1 to 0.5:2.

[0016] Preferably, in step (2), the centrifugation speed is 2000 to 8000 rpm and the time is 5 to 20 min.

[0017] Preferably, in step (3), the mass ratio of the silver nanowire-montmorillonite composite material to the silicone rubber is 0.01 to 0.5:1.

[0018] The heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound prepared by the above method of the present invention can be cured by adding a curing agent at room temperature or high temperature, and is used for preparing room temperature vulcanized silicone rubber, high temperature vulcanized silicone rubber, etc., and has heat-conductive characteristics. The silicone rubber cured by the heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound of the present invention is also one of the present inventions.

[0019] In the compound provided by the present invention, silver nanowires grow in-situ between the montmorillonite layers. Through the interlayer confinement effect of montmorillonite, a three-dimensional heat conduction network is constructed, and the interfacial compatibility between the filler and the silicone rubber is improved, and the heat resistance of the silicone rubber is enhanced. The heat-resistant and heat-conductive silicone rubber compound of the present invention can be used for designing and preparing thermal interface materials. Specifically, the beneficial effects of the present invention are as follows:

[0020] (1) In the present invention, silver nanowires grow in-situ in montmorillonite, realizing the uniform growth of silver nanowires.

[0021] (2) The silver nanowires of the present invention can exfoliate montmorillonite, and the silver nanowires themselves have relatively excellent heat conduction performance, which helps to form a three-dimensional heat conduction network of silver nanowires and montmorillonite in the silicone rubber, improving the heat conduction efficiency and thermal stability of the silicone rubber.

[0022] (3) The silicone rubber compound provided by the present invention has a wide range of applications and excellent thermal conductivity, and can be used in the fields of electronics and electricity, automobiles, aerospace, etc. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the preparation process of the nano silver wire thermally conductive silicone rubber cured product proposed by the present invention;

[0024] Figure 2 It is the (a) TGA and (b) DTG curve graphs of the thermogravimetric analysis test of the silicone rubber of Comparative Example 1 and Examples 1-4 of the present invention;

[0025] Figure 3 It is the SEM diagram of the nano silver wire-montmorillonite composite material prepared in Example 2 of the present invention, where (a) and (b) correspond to different positions;

[0026] Figure 4 It is the TEM diagram of the nano silver wire thermally conductive silicone rubber cured product prepared in Example 3 of the present invention. Detailed Embodiments

[0027] The following details the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0028] Example 1

[0029] This example provides a method for preparing a heat-resistant and thermally conductive nano silver wire-reinforced silicone rubber compound:

[0030] Disperse 2 g of sodium-based montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water, and stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 1.3 million) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask, and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0031] Take 0.34 g of silver nitrate and dissolve it in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in the three-necked flask, heat it to 160 °C, and then add 1.8×10 -4React 10 min at a constant temperature with g of copper chloride. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask simultaneously at a rate of 12 mL / min, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool to room temperature. The obtained product is centrifuged successively with acetone, deionized water, and absolute ethanol at 8000 rpm for 10 min to obtain the silver nanowire-montmorillonite composite material.

[0032] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 2.2 parts of the silver nanowire-montmorillonite composite material. Add the silver nanowire-montmorillonite composite material to the silicone rubber in small amounts and multiple times, stir vigorously to mix evenly, and then obtain the heat-resistant and thermally conductive silver nanowire-reinforced silicone rubber compound through three-roll grinding and ultrasonic treatment. Then add 10 parts of curing agent (platinum complex) and continue to stir vigorously to mix evenly. Then place it in a vacuum oven to remove bubbles for 0.5 h, perform ultrasonic treatment for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the silver nanowire thermally conductive silicone rubber.

[0033] Example 2

[0034] This example provides a method for preparing a heat-resistant and thermally conductive silver nanowire-reinforced silicone rubber compound:

[0035] Disperse 2 g of sodium-based montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water, stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 1.3 million) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask, and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0036] Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in a three-necked flask, heat it to 160 °C, and then add 1.8×10 -4 g of copper chloride and react at a constant temperature for 10 min. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask simultaneously at a rate of 12 mL / min, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool to room temperature. The obtained product is centrifuged successively with acetone, deionized water, and absolute ethanol at 8000 rpm for 10 min to obtain the silver nanowire-montmorillonite composite material.

[0037] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 4.4 parts of the nanosilver wire-montmorillonite composite material. Add the nanosilver wire-montmorillonite composite material to the silicone rubber in small amounts and multiple times, stir vigorously to mix evenly, and then obtain the heat-resistant and heat-conductive nanosilver wire-reinforced silicone rubber compound through three-roll grinding and ultrasonic treatment. Then add 10 parts of a curing agent (platinum complex) and continue to stir vigorously to mix evenly. Then place it in a vacuum oven to remove air bubbles for 0.5 h, perform ultrasonic treatment for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the nanosilver wire heat-conductive silicone rubber.

[0038] Example 3

[0039] This example provides a method for preparing a heat-resistant and heat-conductive nanosilver wire-reinforced silicone rubber compound:

[0040] Disperse 2 g of sodium-based montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water, stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 1.3 million) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask, and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0041] Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in a three-necked flask, heat it to 160 °C, and then add 1.8×10 -4 g of copper chloride and react at a constant temperature for 10 min. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask simultaneously at a rate of 12 mL / min, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool it to room temperature. The obtained product is centrifuged at 8000 rpm for 10 min successively with acetone, deionized water, and absolute ethanol to obtain the nanosilver wire-montmorillonite composite material.

[0042] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 6.6 parts of the nanosilver wire-montmorillonite composite material. Add the nanosilver wire-montmorillonite composite material to the silicone rubber in small amounts and multiple times, stir vigorously to mix evenly, and then obtain the heat-resistant and heat-conductive nanosilver wire-reinforced silicone rubber compound through three-roll grinding and ultrasonic treatment. Then add 10 parts of a curing agent (platinum complex) and continue to stir vigorously to mix evenly. Then place it in a vacuum oven to remove air bubbles for 0.5 h, perform ultrasonic treatment for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the nanosilver wire heat-conductive silicone rubber.

[0043] Example 4

[0044] This embodiment provides a method for preparing a heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound:

[0045] Disperse 2 g of sodium montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water, stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 1.3 million) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask, and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0046] Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in a three-necked flask, heat it to 160 °C, and then add 1.8×10 -4 g of copper chloride and react at a constant temperature for 10 min. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask at a rate of 12 mL / min simultaneously, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool to room temperature, and the obtained product is centrifuged at 8000 rpm for 10 min successively using acetone, deionized water, and absolute ethanol to obtain a nano-silver wire-montmorillonite composite material.

[0047] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 8.8 parts of the nano-silver wire-montmorillonite composite material, and add the nano-silver wire-montmorillonite composite material to the silicone rubber in small amounts and multiple times, stir strongly to mix evenly, and then obtain the heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound through three-roll grinding and ultrasonic treatment. Then add 10 parts of a curing agent (platinum complex) and continue to stir strongly to mix evenly. Then place it in a vacuum oven to remove bubbles for 0.5 h, perform ultrasonic treatment for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the nano-silver wire heat-conductive silicone rubber.

[0048] Example 5

[0049] This embodiment provides a method for preparing a heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound:

[0050] Disperse 2 g of sodium montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water, stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 900,000) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask, and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0051] Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in a three-necked flask, heat it to 160 °C, and then add 1.8×10 -4 g of copper chloride and react at a constant temperature for 10 min. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask simultaneously at a rate of 12 mL / min, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool it to room temperature. The obtained product is centrifuged successively with acetone, deionized water, and absolute ethanol at 8000 rpm for 10 min to obtain the silver nanowire-montmorillonite composite material.

[0052] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 4.4 parts of the silver nanowire-montmorillonite composite material. Add the silver nanowire-montmorillonite composite material to the silicone rubber in small portions and mix well by strong stirring. Then, it is milled with a three-roll mill and treated by ultrasonic treatment to obtain a heat-resistant and thermally conductive silver nanowire-reinforced silicone rubber compound. Then add 10 parts of a curing agent (platinum complex) and continue to mix well by strong stirring. Then put it into a vacuum oven to remove bubbles for 0.5 h, perform ultrasonic treatment for 0.5 h, pour it into a polytetrafluoroethylene mold, and put it into an oven at 100 °C for curing for 2 h to obtain the silver nanowire thermally conductive silicone rubber.

[0053] Example 6

[0054] This example provides a method for preparing a heat-resistant and thermally conductive silver nanowire-reinforced silicone rubber compound:

[0055] Disperse 2 g of calcium-based montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) in 40 mL of deionized water and stir at a speed of 180 r / min for 12 h to obtain a 50 g / L montmorillonite aqueous solution. Then weigh 2.22 g of polyvinylpyrrolidone (Aladdin, molecular weight 1.3 million) and dissolve it in 20 mL of acetic acid (100 g / L) to obtain a polyvinylpyrrolidone solution. Pour the polyvinylpyrrolidone solution and the montmorillonite aqueous solution into a 250 mL three-necked flask and stir at 55 °C for 12 h to obtain a polyvinylpyrrolidone-montmorillonite composite material solution.

[0056] Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain a silver nitrate solution. Take another 20 mL of ethylene glycol in a three-necked flask, heat it to 160 °C, and then add 1.8×10 -4 g of copper chloride and react at a constant temperature for 10 min. Inject the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite mixed solution into the three-necked flask simultaneously at a rate of 12 mL / min, and continue to react at a constant temperature for 1 h. After the reaction is completed, cool it to room temperature. The obtained product is centrifuged successively with acetone, deionized water, and absolute ethanol at 8000 rpm for 10 min to obtain the silver nanowire-montmorillonite composite material.

[0057] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184) and 6.6 parts of the nanosilver wire-montmorillonite composite material. Add the nanosilver wire-montmorillonite composite material to the silicone rubber in small amounts and multiple times, stir strongly to mix evenly, and then obtain the heat-resistant and heat-conductive nanosilver wire-reinforced silicone rubber compound through three-roll grinding and ultrasonic treatment. Then add 10 parts of curing agent (platinum complex) and continue to stir strongly to mix evenly. Then place it in a vacuum oven to defoam for 0.5 h, ultrasonicate for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the nanosilver wire heat-conductive silicone rubber.

[0058] Comparative Example 1

[0059] Weigh 100 parts of silicone rubber (Dow Corning Sylgard 184), and then add 10 parts of curing agent (platinum complex) and stir strongly to mix evenly. Then place it in a vacuum oven to defoam for 0.5 h, ultrasonicate for 0.5 h, pour it into a polytetrafluoroethylene mold, and place it in an oven at 100 °C to cure for 2 h to obtain the silicone rubber.

[0060] Performance Test

[0061] Detect the heat-conductive performance, mechanical performance, and thermal stability performance of the heat-conductive silicone rubbers of Examples 1-4 and Comparative Example 1.

[0062] (1) Test according to the GB / T 11205-2009 standard. Use the QTM500 thermal conductivity tester of Hitachi, Ltd., Japan to test the thermal conductivity (λ) of the specimen.

[0063] (2) According to the GB / T 104032006 standard (Test for Tensile Properties of Plastics), use the Lnstron5967 electronic universal testing machine of Instron Corporation, USA to test the tensile properties of the heat-conductive silicone rubbers prepared in Examples 1-4 and Comparative Example 1.

[0064] (3) Test according to the ASTM D6370-99 standard. Use the STA449F3 thermogravimetric analyzer of Netzsch, Germany to test the thermal stability performance of the heat-conductive silicone rubbers prepared in Examples 1-4 and Comparative Example 1.

[0065] The results are shown in Table 1.

[0066] Table 1 Heat-conductive performance, mechanical performance, and thermal stability performance of the heat-conductive silicone rubbers of Examples 1-4 and Comparative Example 1

[0067]

[0068] It can be seen from Table 1 that: The heat-conductive performance of the silicone rubber added with the nanosilver wire-montmorillonite composite material is significantly better than that of the silicone rubber in the comparative example. The tensile strength and elongation at break of the silicone rubber obtained from the nanosilver wire-montmorillonite composite material in Example 2 increase.

[0069] Figure 2 Curves of (a) TGA and (b) DTG for the thermogravimetric analysis test of the silicone rubbers in Comparative Example 1 and Examples 1-4. From Table 1 and Figure 2 it can be seen that the residual mass of Comparative Example 1 is 40.05%, and T max is 566 °C. Compared with Comparative Example 1, the residual mass and T max of Examples 1-4 are significantly improved. This is because during the degradation process of the silicone rubber, montmorillonite inhibits the breakage of the side chain groups of the silicone rubber and delays the breakage of the main chain silicon-oxygen bonds. The silver nanowire-montmorillonite can be well dispersed in the silicone rubber matrix to form an effective heat conduction network, avoiding local overheating of the silicone rubber, thereby slowing down the degradation rate of the silicone rubber. From Examples 1, 2, 3, 4 and Comparative Example 1, it can be seen that after adding the silver nanowire-montmorillonite composite material, the thermal stability of the silicone rubber has been significantly improved.

[0070] Figure 3 SEM images of the silver nanowire-montmorillonite composite material prepared in Example 2, where (a) and (b) correspond to different positions. It can be seen that very obvious silver nanowires and montmorillonite lamellae can be seen, and a large number of silver nanowires grow out through the lamellae.

[0071] Figure 4 TEM images of the cured silver nanowire heat-conducting silicone rubber prepared in Example 3. It can be clearly seen that montmorillonite lamellae are stacked in the silicone rubber matrix, and at the same time, a small amount of silver nanowires can also be seen.

[0072] When the dosage of the silver nanowire-montmorillonite composite material is 6 wt% (Example 3), the heat-conducting silicone rubber compound of the present invention has the most excellent heat conduction performance; when the dosage of the silver nanowire-montmorillonite composite material is 4 wt% (Example 2), the heat-conducting silicone rubber compound of the present invention has the most excellent mechanical properties; when the dosage of the silver nanowire-montmorillonite composite material is 6 wt% (Example 3), the heat-conducting silicone rubber compound of the present invention has the most excellent thermal stability.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and does not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound, characterized in that: First, polyvinylpyrrolidone is introduced into the interlayer of montmorillonite through the action of hydroxyl groups on the surface of montmorillonite. Then, silver ions are fixed on the polyvinylpyrrolidone-montmorillonite composite material through cation exchange between silver ions and montmorillonite and chelation with the polyvinylpyrrolidone chain. Subsequently, silver ions are in-situ reduced to silver nanowires embedded in the interlayer of montmorillonite by ethylene glycol, obtaining a silver nanowire-montmorillonite composite material. Finally, the silver nanowire-montmorillonite composite material is mixed with silicone rubber under stirring, and a heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound is obtained through grinding and ultrasonic dispersion. The specific steps are as follows: (1) Montmorillonite is added to deionized water and magnetically stirred until evenly dispersed to obtain a montmorillonite aqueous solution; polyvinylpyrrolidone is dissolved in acetic acid to obtain a polyvinylpyrrolidone solution; the polyvinylpyrrolidone solution is mixed with the montmorillonite aqueous solution and heated and stirred to obtain a polyvinylpyrrolidone-montmorillonite composite material solution; (2) Silver nitrate is dissolved in the first portion of ethylene glycol to obtain a silver nitrate solution; another portion of ethylene glycol is taken in a three-necked flask and heated to 120 - 180 °C, and copper chloride is added and reacted at a constant temperature for 5 - 30 min; the silver nitrate solution and the polyvinylpyrrolidone-montmorillonite composite material solution are simultaneously injected into the three-necked flask at a rate of 5 - 20 mL / min and continue to react at a constant temperature for 0.5 - 3 h; after the reaction is completed, it is cooled to room temperature, and the obtained product is centrifugally separated and purified successively using acetone, deionized water, and absolute ethanol to obtain a silver nanowire-montmorillonite composite material; (3) Preparation of silicone rubber compound The silver nanowire-montmorillonite composite material in step (2) is added to silicone rubber, and after stirring, three-roll grinding, and / or ultrasonic treatment, a heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound is obtained.

2. The preparation method of a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound according to claim 1, characterized in that: The montmorillonite is one or any combination of natural montmorillonite, lithium-based montmorillonite, sodium-based montmorillonite, magnesium-based montmorillonite, and calcium-based montmorillonite.

3. The preparation method of a heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound according to claim 1, characterized in that: The molecular weight of the polyvinylpyrrolidone is 30,000 - 1,300,000.

4. The preparation method of a heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound according to claim 1, characterized in that: In step (1), the mass ratio of the montmorillonite to the polyvinylpyrrolidone is 1:0.5 - 2, and the heating and stirring are carried out at 40 - 80 °C for 6 - 18 h.

5. The preparation method of a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound according to claim 1, characterized in that: In step (2), the concentration of the silver nitrate solution is 0.1 - 0.5 g / 20 mL, and the dosage ratio of the silver nitrate solution, the second portion of ethylene glycol, and copper chloride is 20 mL: 20 - 200 mL: 1.0×10 -4 ~1.0×10 -3 g; in step (2), the mass ratio of silver nitrate to montmorillonite in step (1) is 0.1 - 0.5:

2.

6. The preparation method of a heat-resistant and heat-conductive nano silver wire-reinforced silicone rubber compound according to claim 1, characterized in that: The silicone rubber is one or any combination of methyl, vinyl, phenyl, fluoro, and nitrile silicone rubbers.

7. The preparation method of a heat-resistant and heat-conductive nano-silver wire reinforced silicone rubber compound according to claim 1, characterized in that: In step (3), the mass ratio of the silver nanowire-montmorillonite composite material to silicone rubber is 0.01 - 0.5:

1.

8. A heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound prepared by the preparation method according to any one of claims 1 - 7.

9. A silicone rubber, characterized in that: Cured from the heat-resistant and heat-conductive silver nanowire-reinforced silicone rubber compound according to claim 8.

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