High-temperature-resistant heat-conducting silica gel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of heat-conducting silica gel, and relates to high-temperature-resistant heat-conducting silica gel as well as a preparation method and application thereof. The invention provides heat-conducting silica gel, which is prepared from the following raw materials in parts by mass: 10 to 20 parts of silicon rubber matrix, 100 parts of modified heat-conducting filler and 5 to 12 parts of auxiliaries, the preparation method of the modified heat-conducting filler comprises the following steps: adding glutaric anhydride and carnosic acid into a solvent to obtain a modifier, then adding the heat-conducting filler, heating to 60-80 DEG C under the protection of nitrogen, carrying out closed heat preservation for 5-10 hours, and cooling to room temperature to obtain the modified heat-conducting filler. According to the heat-conducting silica gel provided by the invention, the heat-conducting filler is subjected to surface treatment, so that gaps existing at the interface of particles and a polymer are reduced, the interface thermal resistance of the heat-conducting silica gel is reduced, and the high-temperature resistance of the heat-conducting silica gel is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal conductive silicone rubber and relates to a high temperature resistant thermal conductive silicone rubber and a preparation method and application thereof. Background Art

[0002] Thermal conductive materials play an important role in many manufacturing industries such as electronics, electrical, communication lighting, aviation, aerospace, military equipment, motors and electrical appliances, as well as high-tech fields such as nuclear reactors. With the rapid development of integration, miniaturization and high power of modern electronic equipment facilities and semiconductor materials, higher requirements are placed on thermal conductive materials. These occasions not only require thermal conductive materials to provide better thermal conductivity and heat dissipation capabilities, but also require them to have high temperature resistance and insulation properties. Silicone rubber has special advantages. It has the characteristics of high thermal conductivity, good elasticity, electrical insulation, easy deformation under low pressure and good sealing. When replacing ordinary polymers for heat dissipation of electronic or semiconductor components, it can effectively fill the gaps between interfaces and remove the air between the hot and cold interfaces, thereby greatly improving the effectiveness of the radiator. Silicone rubber does not absorb or release heat during vulcanization, can still maintain elasticity for a long time in a wide temperature range, and has excellent electrical properties and chemical stability. It is the preferred material for potting electronic and electrical and communication lighting components. However, the thermal conductivity coefficient (also known as thermal conductivity) of silicone rubber base material (base material) is only 0.1-0.2 W / (m·K), so modification and compounding are required to obtain silicone rubber materials with high thermal conductivity.

[0003] Thermally conductive silicone rubber can be divided into insulating and non-insulating types according to its electrical conductivity, free radical cross-linking, condensation and addition types according to its vulcanization mechanism, single-component and two-component types according to its packaging form, and intrinsic thermally conductive silicone rubber and filled thermally conductive silicone rubber according to its thermal conductivity mechanism. Among them, intrinsic thermally conductive silicone rubber completes heat transfer through the main chain or side chain of silicone rubber macromolecules. Its synthesis process is complex and expensive, and it is currently only in the preliminary research stage. Industrial-scale application is to prepare thermally conductive silicone rubber by filling with high thermal conductivity fillers, that is, filled thermally conductive silicone rubber. Addition-type liquid thermally conductive silicone rubber is the mainstream development direction of thermally conductive silicone rubber composite materials. Addition-type liquid silicone rubber base rubber does not produce low molecular by-products during the cross-linking and curing process, and will not produce destructive stress at high temperatures due to low molecular by-products. Its vulcanization speed has nothing to do with the ambient humidity. It can be cured at low, medium and high temperatures. It has excellent electrical strength and chemical stability. It is weather-resistant, waterproof, moisture-proof, shock-proof, non-corrosive, non-toxic and odorless. It is easy to pour and can be deeply vulcanized. It has very little shrinkage and is easy to operate. It can be used for a long time at -65 to 200°C and exhibits excellent high temperature resistance.

[0004] However, the existing ordinary room temperature vulcanized silicone rubber can only be used at 200°C, and the medium and high temperature vulcanized silicone rubber can only be used for a long time at 250°C and only for a short time at 300°C, which limits its application in higher temperature environments. At the same time, although thermally conductive silicone rubber can be prepared by filling with high thermal conductivity fillers, how to improve the dispersion of fillers, the degree of adhesion with the silicone rubber matrix, and how to form an effective thermal conductive network chain inside the silicone rubber to obtain a high thermal conductivity and high temperature resistant silicone rubber composite material is still an important topic of current research. In summary, the development of a silicone rubber composite material that has both high thermal conductivity and high temperature resistance is of great significance to meet the technical requirements of the fields of electronics, electrical and communication lighting in the contemporary and future. Summary of the invention

[0005] The purpose of the present invention is to provide a high temperature resistant thermally conductive silicone, and to solve the technical problem that it is difficult to balance the thermal conductivity and high temperature resistance of thermally conductive silicone. To this end, the present invention provides a high temperature resistant thermally conductive silicone and its preparation method and application to meet this need in the art.

[0006] On the one hand, the present invention relates to a thermally conductive silicone, which is composed of the following raw materials, measured by mass: 10 to 20 parts of a silicone rubber matrix, 100 parts of a modified thermally conductive filler, and 5 to 12 parts of an auxiliary agent;

[0007] The preparation method of the modified thermal conductive filler comprises: adding glutaric anhydride and carnosic acid into a solvent to obtain a modifier, then adding a thermal conductive filler, heating to 60-80° C. under nitrogen protection, sealing and keeping warm for 5-10 hours, and cooling to room temperature to obtain the modified thermal conductive filler.

[0008] Furthermore, in the thermally conductive silica gel provided by the present invention, the auxiliary agents include: a curing agent, a catalyst, a thermal stabilizer and a coupling agent.

[0009] Furthermore, in the thermally conductive silica gel provided by the present invention, the additives are, by weight, 0.9 to 1.5 parts of a curing agent, 0.1 to 0.5 parts of a catalyst, 1 to 2 parts of a crosslinking inhibitor, 2 to 5 parts of a heat stabilizer, and 1 to 3 parts of a coupling agent.

[0010] Furthermore, in the thermally conductive silica gel provided by the present invention, the silicone rubber matrix is ​​at least one of vinyl silicone oil, methyl silicone oil, methyl vinyl silicone rubber, and methyl phenyl silicone resin;

[0011] The curing agent is at least one of vinyl triamine, ethylenediamine, and m-phenylenediamine;

[0012] The catalyst is chloroplatinic acid or a platinum complex;

[0013] The cross-linking inhibitor is at least one of perchloroethylene, benzotriazole, and alkenylsiloxane;

[0014] The heat stabilizer is at least one of tin oxide, dimethyltin dichloride, and tributyltin chloride;

[0015] The coupling agent is at least one of hexadecyltrimethoxysilane, isopropyl dioleyl acyloxy titanate, and distearoyloxy isopropyl aluminate.

[0016] Furthermore, in the thermally conductive silica gel provided by the present invention, in the modifier, the concentration of glutaric anhydride is 1 to 2 mol / L, and the concentration of carnosic acid is 0.5 to 2 mol / L;

[0017] Every 10 g of the thermally conductive filler corresponds to 20 to 50 mL of the modifier.

[0018] Furthermore, in the thermally conductive silica gel provided by the present invention, the solvent is DMF.

[0019] Furthermore, in the thermally conductive silica gel provided by the present invention, the thermally conductive filler is at least one of boron nitride, aluminum nitride, and aluminum oxide.

[0020] Furthermore, in the thermally conductive silica gel provided by the present invention, the thermally conductive filler contains 1 to 2.5% of needle-shaped γ-phase nano-alumina by mass percentage.

[0021] On the other hand, the present invention relates to a method for preparing the thermally conductive silica gel, which comprises: mixing and solidifying the raw materials.

[0022] On the other hand, the present invention relates to the use of the thermally conductive silicone as a thermal interface material in electronic components.

[0023] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0024] (1) The surface tension of the untreated thermally conductive filler and silicone rubber is very different, and the surface of the thermally conductive filler particles is difficult to be wetted by the polymer. The surface wettability of the thermally conductive filler particles affects the dispersion state of the filler and the degree of adhesion between the filler and the matrix. The untreated filler particles are easily aggregated due to the strong intermolecular forces themselves, and are difficult to effectively disperse in the polymer matrix. There are gaps at the interface between the particles and the polymer, which increases the interfacial thermal resistance of the composite material. The present invention modifies the surface of the thermally conductive filler by glutaric anhydride and carnosic acid, which can facilitate the interface wetting of the thermally conductive filler and silicone rubber, increase adhesion, reduce the gaps at the interface between the particles and the polymer, reduce the interfacial thermal resistance of the thermally conductive silicone rubber and improve its high temperature resistance.

[0025] (2) In practical applications, the thermal conductivity of filled thermally conductive polymer composite materials depends on the polymer matrix, filler and their common interface. When the present invention uses needle-shaped γ-phase nano-alumina as a thermally conductive filler, it can more effectively make the thermally conductive filler ions contact and interact with each other, forming a more rigorous chain-like network structure, which can better overcome the interface thermal resistance. When the orientation of the formed thermal conductive network chain is parallel to the heat flow direction, the thermal conductivity of the system will be greatly improved. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0027] Preparation Example

[0028] This preparation example provides a preparation method for thermally conductive silica gel.

[0029] (1) Preparation of modified thermal conductive filler:

[0030] Step 1: Add glutaric anhydride and carnosic acid to DMF to obtain a modifier, wherein the concentration of glutaric anhydride is 1-2 mol / L, and the concentration of carnosic acid is 0.5-2 mol / L.

[0031] Step 2: Every 10g of thermal conductive filler is mixed with 20-50mL of modifier, stirred at 500rmp for 10min, heated to 70°C under nitrogen protection, sealed and kept warm for 8h, cooled to room temperature, filtered after the reaction is completed, and then dried in a drying oven at 110°C hot air to obtain a modified thermal conductive filler.

[0032] When glutaric anhydride and carnosic acid are sealed and kept at 60-80°C for 5-10 hours, the surface modification of the thermal conductive filler can be achieved well. In the preparation step of the modified thermal conductive filler, no coupling agent is added. The purpose is that when the thermal conductive filler contains needle-shaped γ-phase nano-alumina, the addition of a coupling agent will weaken the improvement effect of the needle-shaped γ-phase nano-alumina on thermal conductivity.

[0033] (2) Preparation of thermally conductive silicone:

[0034] In parts by mass, 10-20 parts of silicone rubber matrix, 100 parts of modified thermal conductive filler, 0.9-1.5 parts of curing agent, 0.1-0.5 parts of catalyst, 1-2 parts of crosslinking inhibitor, 2-5 parts of thermal stabilizer and 1-3 parts of coupling agent are mixed evenly in a high-speed mixer to obtain a base material. The obtained base material is vacuumized. Then it is put into a flat vulcanizer for tableting and curing to obtain a thermal conductive silicone with a thickness of 3 mm.

[0035] The following raw materials can be obtained from the market. Among them, the needle-shaped γ-phase nano-alumina and the spherical γ-phase nano-alumina are purchased from Guangzhou Hongwu Material Technology Co., Ltd., with a particle size of 20 to 30 nm and a purity of 99.99%.

[0036] Table 1: Modified filler formulation

[0037]

[0038] Table 2: Thermally conductive silicone formula

[0039]

[0040]

[0041] Comparative Example 1

[0042] This comparative example is the same as Example 3, except that glutaric anhydride is not added.

[0043] Comparative Example 2

[0044] This comparative example is the same as Example 3, except that carnosic acid is not added.

[0045] Comparative Example 3

[0046] This comparative example is the same as Example 3, except that the thermal conductive filler is not modified.

[0047] Comparative Example 4

[0048] This comparative example is the same as Example 3, except that, in the preparation of the modified thermally conductive filler, 1% hexadecyltrimethoxysilane is added to the modifier.

[0049] Test Case

[0050] This test example is used to illustrate the thermally conductive silica gel performance of Examples 1 to 4 and Comparative Examples 1 to 4.

[0051] In this test example, the tests of tensile strength and elongation at break refer to the standard "ASTM D882-18 Standard Test Method for Tensile Properties of Thin Plastic Sheets". The test of thermal conductivity refers to the standard "ASTM D-5470-01 Characterization Test for Testing Thermal Conductivity Properties of Thin Thermally Conductive Solid Electrical Insulating Materials". The test of thermal expansion coefficient refers to the standard "ASTM D696 Standard Test for Determining the Linear Thermal Expansion Coefficient of Plastics in the Range of -30°C and 30°C Using a Quartz Glass Thermal Dilatometer". The test results are shown in Table 3.

[0052] Table 3: Thermally conductive silicone properties

[0053]

[0054]

[0055] The above test results show that the thermally conductive silicone rubbers of Examples 1 to 4 all exhibit good performance in terms of tensile strength, elongation at break, thermal conductivity and thermal expansion coefficient. Specifically, the thermally conductive silicone rubber of Example 1 has a tensile strength of 1.62 MPa, an elongation at break of 76%, a thermal conductivity of 7.10 W / m·K, and a thermal expansion coefficient of 5.5×10 -5 m / ℃; the thermal conductive silicone of Example 2 has a slightly higher tensile strength of 1.68MPa, a similar elongation at break of 77%, a higher thermal conductivity of 7.93W / m·K, and a slightly lower thermal expansion coefficient of 5.2×10 -5 m / ℃; the thermal conductive silica gel of Example 3 has a tensile strength of 1.66MPa, an elongation at break of 76%, a thermal conductivity of 7.22W / m·K, and a thermal expansion coefficient of 5.9×10 -5 m / ℃; The tensile strength of the thermally conductive silicone in Example 4 is slightly lower, which is 1.50 MPa, the elongation at break is 71%, the thermal conductivity is reduced to 6.11 W / m·K, and the thermal expansion coefficient is increased to 6.4×10 -5 m / ℃.

[0056] In contrast, the thermally conductive silica gels of Comparative Examples 1 to 4 have poor performance. In Comparative Example 1, glutaric anhydride was not added, and the tensile strength, elongation at break and thermal conductivity of the thermally conductive silica gel were significantly reduced to 1.43 MPa, 70% and 3.85 W / m·K, respectively, and the thermal expansion coefficient increased to 7.3×10 -5 m / ℃; In comparative example 2, carnosic acid was not added, and its performance also decreased, with a tensile strength of 1.48MPa, an elongation at break of 72%, a thermal conductivity of 3.09W / m·K, and a thermal expansion coefficient of 7.5×10 - 5 m / ℃; The thermal conductive filler of Comparative Example 3 was not modified and had the worst performance, with a tensile strength of 1.36MPa, an elongation at break of 64%, a thermal conductivity of 2.06W / m·K, and a thermal expansion coefficient of 82×10 -5 m / ℃; Comparative Example 4 adds 1% hexadecyltrimethoxysilane to the modifier. Although its thermal conductivity is improved compared with the unmodified one (5.84 W / m·K), it is still lower than that in the embodiment. The tensile strength, elongation at break and thermal expansion coefficient also do not reach the level of the embodiment, which are 1.52 MPa, 70% and 6.8×10 -5 m / ℃.

[0057] In summary, the thermally conductive silicone in the embodiment significantly improves the thermal conductivity through a specific modified thermally conductive filler preparation method and formulation, while maintaining good mechanical properties and thermal stability. However, the thermally conductive silicone in the comparative example has relatively poor performance due to the lack of key components or the lack of necessary modification treatment.

[0058] The embodiments described above are part of the embodiments of the present invention, but not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A thermally conductive silica gel, characterized in that: The composition is composed of the following raw materials in parts by mass: 10 to 20 parts of silicone rubber matrix, 100 parts of modified thermal conductive filler and 5 to 12 parts of auxiliary agent; The preparation method of the modified thermal conductive filler comprises: adding glutaric anhydride and carnosic acid into a solvent to obtain a modifier, then adding a thermal conductive filler, heating to 60-80° C. under nitrogen protection, sealing and keeping warm for 5-10 hours, and cooling to room temperature to obtain the modified thermal conductive filler.

2. The thermally conductive silica gel according to claim 1, characterized in that: The auxiliary agents include: a curing agent, a catalyst, a heat stabilizer and a coupling agent.

3. The thermally conductive silica gel according to claim 2, characterized in that: In parts by mass, the auxiliary agents include 0.9 to 1.5 parts of a curing agent, 0.1 to 0.5 parts of a catalyst, 1 to 2 parts of a crosslinking inhibitor, 2 to 5 parts of a heat stabilizer, and 1 to 3 parts of a coupling agent.

4. The thermally conductive silica gel according to claim 2, characterized in that: The silicone rubber matrix is ​​at least one of vinyl silicone oil, methyl silicone oil, methyl vinyl silicone rubber, and methyl phenyl silicone resin; The curing agent is at least one of vinyl triamine, ethylenediamine, and m-phenylenediamine; The catalyst is chloroplatinic acid or a platinum complex; The cross-linking inhibitor is at least one of perchloroethylene, benzotriazole, and alkenylsiloxane; The heat stabilizer is at least one of tin oxide, dimethyltin dichloride, and tributyltin chloride; The coupling agent is at least one of hexadecyltrimethoxysilane, isopropyl dioleyl acyloxy titanate, and distearoyloxy isopropyl aluminate.

5. The thermally conductive silica gel according to claim 1, characterized in that: In the modifier, the concentration of glutaric anhydride is 1-2 mol / L, and the concentration of carnosic acid is 0.5-2 mol / L; Every 10 g of the thermally conductive filler corresponds to 20 to 50 mL of the modifier.

6. The thermally conductive silica gel according to claim 1, characterized in that: The solvent is DMF.

7. The thermally conductive silica gel according to claim 1, characterized in that: The thermally conductive filler is at least one of boron nitride, aluminum nitride, and aluminum oxide.

8. The thermally conductive silica gel according to claim 7, characterized in that: In terms of mass percentage, the thermal conductive filler contains 1-2.5% of needle-shaped γ-phase nano-alumina.

9. The method for preparing the thermally conductive silica gel according to any one of claims 1 to 8, characterized in that: include: The raw materials are mixed and solidified to obtain.

10. Use of the thermally conductive silicone according to any one of claims 1 to 8 as a thermal interface material in electronic components.

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