Highly heat-conductive silica gel and preparation method thereof

Abstract

The application discloses a high-thermal-conductivity silica gel and a preparation method thereof, and belongs to the technical field of high polymer composite materials.The composition comprises the following components in parts by weight: 100 parts of vinyl silicone oil, 10-20 parts of hydrogen-containing silicone oil, 0.1-1 part of a platinum gold catalyst, 1-5 parts of a silane coupling agent, 50-200 parts of functional fillers, and 0.03-0.1 part of an inhibitor.The functional fillers comprise carbon nanofiber / ZnO / MgO composite materials and alumina with a particle size of 10-30 nm treated by the silane coupling agent.The functional fillers endow the high-thermal-conductivity silica gel with excellent thermal conductivity, flame retardation and electromagnetic wave absorption performance, and the high-thermal-conductivity silica gel can be widely applied to thermal management and electromagnetic protection in the fields of new energy vehicles, aerospace and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a high thermal conductivity silicone and its preparation method. Background Technology

[0002] With the rapid development of high-tech fields such as 5G communication, new energy vehicles, and aerospace, the integration of electronic devices is constantly increasing, and the power density is continuously rising, leading to a sharp increase in heat generation. Overheating has become a key factor restricting the performance and reliability of electronic devices. At the same time, electromagnetic interference is becoming increasingly prominent, and the fire safety risks cannot be ignored. Therefore, developing multifunctional thermal management materials that combine high thermal conductivity, excellent flame retardancy, and good microwave absorption properties is of significant practical importance.

[0003] Silicone is widely used as an electronic packaging material and thermally conductive substrate due to its excellent resistance to high and low temperatures, chemical stability, and flexibility. However, pure silicone has extremely low thermal conductivity, which cannot meet heat dissipation requirements; at the same time, silicone is flammable and does not have electromagnetic wave absorption capabilities. Therefore, functional fillers are usually added to silicone to improve its overall performance.

[0004] In existing technologies, common fillers include alumina, boron nitride, silicon carbide, graphene, and carbon nanotubes. However, it is difficult to construct an efficient thermally conductive network with a single filler, and it is also difficult to simultaneously achieve multiple functions such as thermal conduction, flame retardancy, and microwave absorption.

[0005] To address the aforementioned problems, this invention provides a composite thermally conductive filler with a multi-level structure and its silicone composition. Through microstructure design and interface control, it achieves integrated thermal conductivity, flame retardancy, and wave absorption properties. Summary of the Invention

[0006] The present invention aims to provide a thermally conductive silicone composition and its preparation method to solve the technical problem that thermally conductive silicone in the prior art is difficult to achieve high thermal conductivity, flame retardancy and electromagnetic wave absorption performance at the same time, and to provide a silicone material with a three-dimensional thermally conductive network of "point-line-surface", good flame retardancy and electromagnetic wave absorption capability.

[0007] A thermally conductive silicone composition, characterized in that it comprises the following components in parts by weight: 100 parts of vinyl silicone oil; 10-20 parts of hydrogen-containing silicone oil; 0.1-1 parts of platinum catalyst; 1-5 parts of silane coupling agent; 50-200 parts of functional filler; 0.03-0.1 parts of inhibitor; wherein the functional filler includes carbon nanofiber / ZnO / MgO composite material and alumina with a particle size of 10-30 nm treated with silane coupling agent; The preparation process of the carbon nanofiber / ZnO / MgO composite material includes the following steps: Step 1: Dissolve polyvinylpyrrolidone and zinc acetate in a solvent to obtain a spinning precursor solution, and obtain nanofibers by electrospinning technology; Heat-treat the composite nanofibers under an inert atmosphere to carbonize PVP and decompose zinc acetate to obtain carbon nanofiber / ZnO composite material. Step 2: Dissolve the magnesium source in a mixed solvent of isopropanol and water, adjust the pH to 7.5-8.0 to obtain a reaction solution; disperse the carbon nanofiber / ZnO composite material in the reaction solution, transfer it to a polytetrafluoroethylene reactor, and carry out the reaction under microwave-assisted heating conditions; Step 3: Wash and dry the product after the reaction in Step 2, and then heat it at 500-600℃ under an inert atmosphere to obtain a filler of nanosheet magnesium oxide grown on the surface of carbon nanofibers / ZnO.

[0008] In a specific embodiment, in step 1, the mass ratio of PVP to zinc acetate is 1:0.5 to 1:2; the solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, or ethanol; the electrospinning voltage is 10-25kV, and the receiving distance is 10-20cm.

[0009] In a specific embodiment, in step 1, the heat treatment temperature is 600-900℃, the heating rate is 2-10℃ / min, and the holding time is 1-3 hours; the inert atmosphere is nitrogen or argon.

[0010] In a specific embodiment, in step 3, the magnesium source is one or more of magnesium nitrate, magnesium acetate, or magnesium chloride; the volume ratio of isopropanol to water is 2:1 to 4:1; the microwave-assisted heating reaction temperature is 150-180℃, and the reaction time is 20-60 minutes.

[0011] In a specific embodiment, the silane coupling agent is one or more of γ-glycidoxypropyltrimethoxysilane (KH-560) and γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0012] In a specific embodiment, the preparation method of the nano-alumina treated with silane coupling agent is as follows: nano-alumina with a particle size of 10-30nm is dispersed in anhydrous ethanol, 1%-5% of silane coupling agent by mass of alumina is added, the mixture is stirred and reacted at 50-80℃ for 2-4 hours, and after centrifugation and drying, surface-modified nano-alumina is obtained.

[0013] In a specific embodiment, the preparation method of the thermally conductive silicone composition includes the following steps: (1) preparing carbon nanofiber / ZnO / MgO composite material; (2) preparing nano-alumina treated with silane coupling agent; (3) dispersing the carbon nanofiber / ZnO / MgO composite material and nano-alumina treated with silane coupling agent in a mass ratio of 1:0.5~1:1 in a volatile organic solvent, ultrasonically treating for 30-60 minutes, drying to remove the solvent, and obtaining a filler mixture; (4) mixing vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, silane coupling agent, and the filler mixture obtained in step (3) and inhibitor evenly, degassing and curing to obtain thermally conductive silicone.

[0014] Beneficial technical effects: (1) The present invention constructs a three-dimensional thermal conductive network of “point-line-surface”, with one-dimensional carbon nanofibers as the thermal conductive framework, ZnO nanoparticles and nanosheet MgO synergistically constructing multi-level thermal conductive pathways, and with the gap filling of nano alumina, a dense and continuous thermal conductive network is formed, which significantly improves the thermal conductivity.

[0015] (2) MgO nanosheets can absorb some heat at high temperatures and form a dense ceramic barrier layer, which delays the internal temperature rise of the material and improves the flame retardancy of thermally conductive silicone.

[0016] (3) The composite material of the present invention contains a large number of heterogeneous interfaces: carbon fiber / ZnO interface, ZnO / MgO interface, MgO / silica gel interface, etc. Under the action of alternating electromagnetic field, the interface polarization loss can generate significant dielectric polarization loss, and the unique "fiber-nanosheet" multi-level structure endows the material with a large specific surface area and structural complexity. Electromagnetic waves will undergo multiple reflections and scatterings in this microstructure, which prolongs the propagation path of electromagnetic waves inside the material and increases the probability of being absorbed by loss.

[0017] (4) The multifunctional synergistic effect makes the silicone composition of the present invention particularly suitable for cutting-edge fields with high requirements for comprehensive performance, such as 5G communication base stations, new energy vehicle battery packs, aerospace electronic equipment, etc. Attached Figure Description

[0018] Figure 1 This is a SEM image of the carbon nanofiber / ZnO / MgO composite material of the present invention, which shows that nanosheet magnesium oxide is uniformly grown on the fiber surface. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] Example 1 (1) Preparation of carbon nanofiber / ZnO / MgO composite material Step 1: Dissolve 2g PVP and 2g zinc acetate in 10mL DMF and stir magnetically for 8 hours to obtain a spinning precursor solution. Electrospinning is then performed at 18kV, a receiving distance of 15cm, and a feed rate of 1mL / h to obtain PVP / Zn(Ac)2 composite nanofibers.

[0021] Step 2: Place the fibers obtained in Step 1 in a tube furnace, heat to 650°C at 5°C / min under a nitrogen atmosphere, hold for 2 hours, and cool naturally to obtain carbon nanofiber / ZnO composite material.

[0022] Step 3: Dissolve 1.2g of magnesium nitrate in a mixed solvent of 60mL isopropanol and 20mL water, adjust the pH to 8.0, add 1g of the composite material obtained in Step 2, and ultrasonically disperse for 10 minutes. Transfer to a polytetrafluoroethylene reactor, microwave-assisted heating, and react at 150℃ for 30 minutes.

[0023] Step 4: The reaction product was washed three times each with deionized water and ethanol, and dried at 60°C for 12 hours. Then, under a nitrogen atmosphere, the temperature was increased to 550°C at 5°C / min and held for 1.5 hours to obtain the carbon nanofiber / ZnO / MgO composite material.

[0024] (2) Surface modification of nano-alumina Take 5g of nano-alumina with a particle size of 10-30nm, disperse it in 100mL of anhydrous ethanol, add 0.3g of KH-560 silane coupling agent, stir and react at 60℃ for 3 hours, centrifuge, and dry at 60℃ for 12 hours to obtain surface-modified nano-alumina.

[0025] (3) Mixed packing Take 3g of the carbon nanofiber / ZnO / MgO composite material obtained in step (1) and 3g of the modified nano-alumina obtained in step (2), disperse them together in 100mL of anhydrous ethanol, and sonicate for 45 minutes. Then remove the solvent by rotary evaporation at 50℃ to obtain the filler mixture.

[0026] (4) Preparation of thermally conductive silicone composition Prepare the raw materials according to the following weight ratio: vinyl silicone oil: 100 parts; hydrogen-containing silicone oil (0.8% hydrogen content): 15 parts; platinum catalyst (3000ppm platinum content): 0.5 parts; KH-560 silane coupling agent: 3 parts; filler mixture obtained in step (3): 80 parts; inhibitor acetylene cyclohexanol: 0.05 parts; add the above components to a planetary mixer and stir under vacuum for 45 minutes to mix evenly; pour into a mold and cure at 100°C for 45 minutes to obtain a thermally conductive silicone composition.

[0027] Example 2 (1) Preparation of carbon nanofiber / ZnO / MgO composite material Step 1: Dissolve 2g PVP and 2g zinc acetate in 10mL DMF and stir magnetically for 8 hours to obtain a spinning precursor solution. Electrospinning technology is used at 18kV and a receiving distance of 15cm to obtain PVP / Zn(Ac)2 composite nanofibers.

[0028] Step 2: Place the fibers obtained in Step 1 in a tube furnace, heat to 700℃ at 5℃ / min under a nitrogen atmosphere, hold for 2 hours, and cool naturally to obtain carbon nanofiber / ZnO composite material.

[0029] Step 3: Dissolve 1.2g of magnesium nitrate in a mixed solvent of 40mL isopropanol and 20mL water, adjust the pH to 8.0, add 1g of the composite material obtained in Step 2, and ultrasonically disperse for 10 minutes. Transfer to a polytetrafluoroethylene reactor, and microwave-assisted heating reaction at 160℃ for 30 minutes.

[0030] Step 4: The reaction product was washed three times each with deionized water and ethanol, and dried at 60°C for 12 hours. Then, under a nitrogen atmosphere, the temperature was increased to 550°C at 5°C / min and held for 1.5 hours to obtain the carbon nanofiber / ZnO / MgO composite material.

[0031] (2) Surface modification of nano-alumina Take 5g of nano-alumina with a particle size of 10-30nm, disperse it in 100mL of anhydrous ethanol, add 0.3g of KH-560 silane coupling agent, stir and react at 60℃ for 3 hours, centrifuge, and dry at 60℃ for 12 hours to obtain surface-modified nano-alumina.

[0032] (3) Mixed packing Take 3g of the carbon nanofiber / ZnO / MgO composite material obtained in step (1) and 2g of the modified nano-alumina obtained in step (2), disperse them together in 100mL of anhydrous ethanol, and sonicate for 45 minutes. Then remove the solvent by rotary evaporation at 50℃ to obtain the filler mixture.

[0033] (4) Preparation of thermally conductive silicone composition Prepare the raw materials according to the following weight ratio: vinyl silicone oil: 100 parts; hydrogen-containing silicone oil (0.5% hydrogen content): 15 parts; Platinum catalyst (platinum content 3000ppm): 0.5 parts; KH-560 silane coupling agent: 3 parts; filler mixture obtained in step (3): 80 parts; inhibitor acetylene cyclohexanol 0.05 parts; add the above components to a planetary mixer, stir under vacuum for 45 minutes, mix evenly; pour into a mold, cure at 100℃ for 45 minutes to obtain thermally conductive silicone.

[0034] Comparative Example 1 It is basically the same as Example 1, except that MgO nanosheets are not generated on the outside of the composite fiber, that is, the carbon nanofiber / ZnO composite material obtained in step 2 is used directly.

[0035] Comparative Example 2 It is basically the same as Example 1, except that no nano-alumina is added.

[0036] Comparative Example 3 The difference from the example is that zinc acetate is not added during the electrospinning process.

[0037] The performance of the silicone compositions obtained in Examples 1-2 and Comparative Examples 1-3 was tested using the following methods: Table 1:

[0038] The performance test results of the silicone compositions obtained in Examples 1-2 and Comparative Examples 1-3 are shown in Table 2: Table 2:

[0039] The invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A thermally conductive silicone composition, characterized in that, The product comprises the following components in parts by weight: 100 parts vinyl silicone oil; 10-20 parts of hydrogen-containing silicone oil; Platinum catalyst 0.1-1 parts; silane coupling agent 1-5 parts; functional filler 50-200 parts; inhibitor 0.03-0.1 parts; the functional filler includes carbon nanofiber / ZnO / MgO composite material and alumina with a particle size of 10-30 nm treated with silane coupling agent; The preparation process of the carbon nanofiber / ZnO / MgO composite material includes the following steps: Step 1: Dissolve polyvinylpyrrolidone and zinc acetate in a solvent to obtain a spinning precursor solution, and obtain nanofibers by electrospinning technology; Heat-treat the composite nanofibers under an inert atmosphere to carbonize PVP and decompose zinc acetate to obtain carbon nanofiber / ZnO composite material. Step 2: Dissolve the magnesium source in a mixed solvent of isopropanol and water, adjust the pH to 7.5-8.0 to obtain a reaction solution; disperse the carbon nanofiber / ZnO composite material in the reaction solution, transfer it to a polytetrafluoroethylene reactor, and carry out the reaction under microwave-assisted heating conditions; Step 3: Wash and dry the product after the reaction in Step 2, and then heat it at 500-600℃ under an inert atmosphere to obtain a filler of nanosheet magnesium oxide grown on the surface of carbon nanofibers / ZnO.

2. The thermally conductive silicone composition according to claim 1, characterized in that, In step 1, the mass ratio of PVP to zinc acetate is 1:0.5 to 1:2; the solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, or ethanol; the electrospinning voltage is 10-25kV, and the receiving distance is 10-20cm.

3. The thermally conductive silicone composition according to claim 1, characterized in that, In step 1, the heat treatment temperature is 600-900℃, the heating rate is 2-10℃ / min, and the holding time is 1-3 hours; the inert atmosphere is nitrogen or argon.

4. The thermally conductive silicone composition according to claim 1, characterized in that, In step 3, the magnesium source is one or more of magnesium nitrate, magnesium acetate, or magnesium chloride; the volume ratio of isopropanol to water is 2:1 to 4:1; the microwave-assisted heating reaction temperature is 150-180℃, and the reaction time is 20-60 minutes.

5. The thermally conductive silicone composition according to claim 1, characterized in that, The silane coupling agent is one or both of γ-glycidoxypropyltrimethoxysilane (KH-560) and γ-methacryloyloxypropyltrimethoxysilane (KH-570).

6. The thermally conductive silicone composition according to claim 1, characterized in that, The preparation method of the nano-alumina treated with silane coupling agent is as follows: nano-alumina with a particle size of 10-30nm is dispersed in anhydrous ethanol, 1%-5% of silane coupling agent by mass of alumina is added, and the mixture is stirred and reacted at 50-80℃ for 2-4 hours. After centrifugation and drying, surface-modified nano-alumina is obtained.

7. A method for preparing the thermally conductive silicone composition according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of carbon nanofiber / ZnO / MgO composite material; (2) Preparation of nano-alumina treated with silane coupling agent; (3) Disperse the carbon nanofiber / ZnO / MgO composite material and nano alumina treated with silane coupling agent in a mass ratio of 1:0.5~1:1 in a volatile organic solvent, sonicate for 30-60 minutes, dry to remove solvent, and obtain a filler mixture; (4) Mix vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, silane coupling agent and the thermally conductive and flame-retardant filler mixture obtained in step (3) and inhibitor evenly, degas and cure to obtain thermally conductive silicone.

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