A high thermal conductivity wave-absorbing rubber sheet and its preparation method

Abstract

The present invention discloses a high thermal conductivity and wave-absorbing rubber sheet and a preparation method thereof. The raw materials for preparation include, by mass parts, 100 parts of vinyl silicone oil, 200 - 800 parts of carbonyl iron, 100 - 300 parts of silicon carbide, 100 - 300 parts of phase change microcapsules, 400 - 1000 parts of diamond, 2 - 8 parts of crosslinking agent, 0.1 - 0.8 part of inhibitor, 0.1 - 0.8 part of platinum catalyst, and 1 - 5 parts of coupling agent. The preparation method is as follows: Add vinyl silicone oil, carbonyl iron, silicon carbide, phase change microcapsules, diamond, and coupling agent into a mixer and stir evenly at high temperature. After the materials are cooled, add the crosslinking agent, inhibitor, and platinum catalyst and stir evenly. Finally, obtain the high thermal conductivity and wave-absorbing rubber sheet through vacuum defoaming, calendering into sheets, and hot air vulcanization. The present invention uses the magnetic material flaky carbonyl iron to be compounded with silicon carbide and diamond, and adds phase change microcapsules, significantly improving the wave-absorbing efficiency and thermal conductivity of the rubber material.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional polymer composite materials, and particularly relates to a high thermal conductivity wave-absorbing rubber sheet and a preparation method thereof. Background Art

[0002] A rubber wave-absorbing material refers to a functional material that can convert electromagnetic waves into heat energy or other forms of energy through electrical loss or magnetic loss, achieving the function of absorbing most or even all of the electromagnetic waves. The wave-absorbing material can be used as an effective radar stealth and highly sensitive anti-electromagnetic wave interference medium, and has wide applications in military stealth, wave absorption of microwave devices, anti-electromagnetic interference in electronic communication, etc.

[0003] With the improvement of the power and integration degree of electronic devices, the internal power density is getting higher and higher, and a large amount of heat is generated during the use of the devices. Due to the small internal space of electronic devices and poor air circulation, the heat is difficult to conduct and radiate to the outside in a timely manner, resulting in an increase in the temperature of electronic devices and components, and a decrease in the working performance of the devices. Therefore, flexible thermally conductive rubber can be used to solve the problem of heat dissipation of electronic components, and timely conduct the heat generated inside the electronic device to avoid the problem of overheating of electronic components. In addition, wave-absorbing materials can be used to solve problems such as electromagnetic interference and information leakage inside electronic devices. Due to the small internal space of electronic devices, the flexible thermally conductive rubber has occupied the gap space of the components, and it is difficult to stack and use wave-absorbing gaskets. Therefore, it is necessary to develop a thermally conductive wave-absorbing material that has a high thermal conductivity coefficient and certain wave-absorbing performance on the one hand, and can effectively solve the problems of heat dissipation and electromagnetic interference inside electronic devices at the same time. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a high thermal conductivity wave-absorbing rubber sheet and a preparation method thereof. The present invention uses liquid silicone rubber as the matrix, diamond and phase change microcapsules as thermal conductive fillers, flaky carbonyl iron and silicon carbide as wave-absorbing fillers, and preferably processing aids and cross-linking systems, thereby obtaining a rubber sheet with high thermal conductivity and wave absorption.

[0005] The raw materials of the high thermal conductivity wave-absorbing rubber sheet are calculated by mass, and include 100 parts of vinyl silicone oil, 200 - 800 parts of carbonyl iron, preferably 300 - 500 parts, 100 - 300 parts of silicon carbide, preferably 100 - 200 parts, 100 - 300 parts of phase change microcapsules, preferably 100 - 150 parts, 400 - 1000 parts of diamond, preferably 500 - 800 parts, 2 - 8 parts of cross-linking agent, preferably 3 - 4.5 parts, 0.1 - 0.8 part of inhibitor, preferably 0.3 - 0.4 part, 0.1 - 0.8 part of platinum catalyst, preferably 0.5 - 0.6 part, and 1 - 5 parts of coupling agent, preferably 3 - 4 parts.

[0006] The coupling agent is one or more of silane coupling agents, stearic acid, and unsaturated organic acids.

[0007] The vinyl silicone oil is one or more of vinyl-terminated polydimethylsiloxane, terminal-side vinyl silicone oil, terminal-methyl-side vinyl silicone oil, and partially-terminated vinyl silicone oil. The viscosity of the vinyl silicone oil is 100 - 400 mPa·s.

[0008] The crosslinking agent is one or more of hydrogen-terminated polydimethylsiloxane, polydimethylmethylhydrogensiloxane, hydrogen-terminated polydimethylmethylhydrogensiloxane, and partially hydrogen-terminated polydimethylsiloxane. The viscosity of the crosslinking agent is 10 - 15 mPa·s.

[0009] The iron carbonyl is a lamellar iron carbonyl wave absorber with a D50 particle size of 2 - 8 μm. The lamellar iron carbonyl wave absorber has the characteristics of high dielectric constant and high magnetic loss. Compared with the traditional spherical iron carbonyl magnetic filler, it can effectively absorb electromagnetic waves at low frequencies.

[0010] The silicon carbide is a spherical thermal conductive and wave absorbing material with a D50 particle size of 30 - 60 μm. Silicon carbide belongs to a resistive wave absorbing material, and the electromagnetic energy is mainly attenuated on the material resistance; it also has excellent thermophysical properties, especially high temperature resistance, high strength, low creep, high thermal conductivity, small expansion coefficient, strong corrosion resistance, and good chemical stability.

[0011] The diamond is an irregular polyhedron with a D50 particle size of 90 - 150 μm, preferably 100 - 130 μm. Diamond is a mineral composed of carbon elements and is an allotrope of graphite; it has the characteristics of high hardness, high melting point, high insulation, chemical stability, acid and alkali corrosion resistance, etc.; the diamond atoms are composed of a pure carbon main chain, which is a structure that can effectively conduct heat.

[0012] The phase change microcapsule is a spherical phase change material with a core / shell structure and a phase change temperature of 37 - 45 °C, and the D50 is 1 - 20 μm, preferably 10 - 20 μm. When the phase change microcapsule reaches the phase change temperature, it absorbs a part of the heat by phase change endotherm; in addition, it can improve the mechanical properties of the system, and at the same time has little effect on the thermal conductivity of the composite material. The shell material of the phase change microcapsule is a composite polymer material, and the core material is paraffin. When the temperature reaches the phase change temperature, the internal paraffin of the shell material absorbs heat and then softens and deforms, but the outer shell material can continue to maintain the spherical shell structure, so the permanent solidification of the phase change material is realized; it has the characteristics of high heat storage capacity, effectively alleviating the equipment heating efficiency, eliminating the heating peak, and extending the temperature control time; in addition, there is no deformation during the phase change.

[0013] The inhibitor is selected from one or more of ethynylcyclohexanol, 3-methyl-1-dodecyn-3-ol, and 3,5-dimethyl-1-ethyn-3-ol.

[0014] The platinum catalyst is in powder form or silicone oil form, and the platinum content is 1000 - 8000 ppm.

[0015] The preparation method of the high - thermal - conductivity wave - absorbing rubber sheet is as follows: Add vinyl silicone oil, carbonyl iron, silicon carbide, phase - change microcapsules, diamond, and coupling agent into a double - planetary mixer, stir and mix evenly at high temperature, wait for the material to cool, then add cross - linker, inhibitor, and platinum catalyst into the double - planetary mixer and stir and mix evenly again. Finally, obtain the high - thermal - conductivity wave - absorbing rubber sheet through vacuum degassing, calendering into sheets, and hot - air vulcanization.

[0016] The temperature of the high - temperature stirring and mixing is 160 - 180 °C, and the stirring time is 30 - 60 min.

[0017] The temperature of the second stirring and mixing is not higher than 30 °C, and the stirring time is 30 - 60 min.

[0018] The temperature of the vacuum degassing is not higher than 40 °C, and the time is 30 - 60 min.

[0019] The temperature of the calendering into sheets is 10 - 60 °C, and the thickness is 0.5 - 10 mm.

[0020] The temperature of the hot - air vulcanization is 100 - 130 °C, and the time is 10 - 30 min.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The present invention uses magnetic material flaky carbonyl iron in compound with silicon carbide and diamond. Through the synergistic effect of iron - based wave - absorbing filler and carbon - based wave - absorbing filler, the wave - absorbing efficiency is improved, solving the problems of poor low - frequency wave - absorbing performance and narrow wave - absorbing frequency of the rubber wave - absorbing sheet, achieving a good thermal - conductivity wave - absorbing effect. The rubber wave - absorbing sheet (thickness 2.0 mm) prepared can reach a maximum wave - absorbing rate of - 20 dB in the 3 - 20 GHz band.

[0023] The present invention uses carbon - based thermal - conductive materials diamond, silicon carbide in compound with phase - change microcapsules to replace traditional alumina and aluminum nitride. It has excellent thermal - conductive performance, with a thermal - conductivity coefficient up to 6 W / mK, good chemical stability, solving the problems of low thermal - conductivity coefficient of alumina and poor chemical stability of aluminum nitride. Due to the special core - shell structure of the phase - change microcapsule material, it can still remain solid after heating. Through the internal paraffin changing from solid to liquid, the endothermic process is realized, thereby reducing the thermal resistance of the thermal - conductive rubber sheet to achieve the rapid export of heat. Different from traditional phase - change thermal - conductive materials, while retaining the phase - change endothermic characteristics, it solves the problems of deformation and even exudation during phase change.

[0024] By selecting different types of coupling agents and choosing appropriate addition amounts according to the particle sizes and morphologies of different powders, the powders, vinyl silicone oil, and coupling agent are added to a blender and subjected to secondary treatment through high-temperature mixing. This solves the dispersion problem during the compounding and mixing of different thermally conductive and wave-absorbing powders, greatly reduces the viscosity of the materials during processing, and improves the effectiveness of the uniform mixing of different materials.

[0025] By selecting different types of vinyl silicone oil and / or hydrogen-containing silicone oil for compounding, the problem of molding and vulcanization is solved, and the problem of gasket cracking caused by partial cross-linking is improved. Specific implementation manners

[0026] The following specifically describes the present invention in combination with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0027] The amounts of each raw material in the examples and comparative examples are based on mass parts.

[0028] Reference standards for performance testing:

[0029] Rubber test: GB / T 6038-2006 Rubber test compounding, mixing and vulcanizing equipment and operating procedures.

[0030] Mechanical properties: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0031] Thermal conductivity: GB / T 29313-2012 Test method for thermal conductivity of electrical insulating materials.

[0032] Wave-absorbing performance: GJB 2038A-2011 Test method for reflectivity of radar absorbing materials.

[0033] Example 1

[0034] The formula is shown in Table 1.

[0035] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.5%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 2 μm; the silicon carbide has a spherical structure with a D50 particle size of 30 μm; the phase change microcapsule is a spherical phase change material with a core / shell structure, with a D50 particle size of 10 μm and a phase change temperature of 45 °C (Hefei Xineng Phase Change New Materials Technology Co., Ltd., PCM-45 (45 °C)); the diamond has an irregular polyhedron shape with a D50 particle size of 100 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 10 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0036] The preparation process conditions are as follows: Weigh accurately according to the mass ratio of each component in Example 1 of Table 1. First, mix the vinyl silicone oil, iron carbonyl, silicon carbide, phase change microcapsule, diamond, and coupling agent in a double planetary mixer at a high temperature of 160 °C for 40 min. After the material cools to room temperature, add other raw materials and mix for 40 min to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber compound mixture at room temperature for 40 min, and roll it into sheets through a rolling equipment at a rolling temperature of 30 °C and a thickness of 2 mm. Transfer the rolled sheet to a hot air drying tunnel with a hot air temperature of 120 °C for 20 min to obtain the high thermal conductivity wave-absorbing rubber sheet.

[0037] Example 2

[0038] The formula is shown in Table 1.

[0039] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.5%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 4 μm; the silicon carbide has a spherical structure with a D50 particle size of 40 μm; the phase change microcapsule is a spherical phase change material with a core / shell structure, with a D50 particle size of 10 μm and a phase change temperature of 45 °C (Hefei Xineng Phase Change New Materials Technology Co., Ltd., PCM-45 (45 °C)); the diamond has an irregular polyhedron shape with a D50 particle size of 100 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 10 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0040] The preparation process conditions are as follows: Weigh accurately according to the mass ratio of each component in Example 2 of Table 1. First, put vinyl silicone oil, iron carbonyl, silicon carbide, phase change microcapsules, diamond, and coupling agent into a double planetary mixer, and mix them at a high temperature of 160 °C for 40 min. After the material is cooled to room temperature, add other raw materials and mix for 40 min to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber compound mixture at room temperature for 40 min, and roll it into sheets through a rolling equipment. The rolling temperature is 30 °C and the thickness is 2 mm. Transfer the rolled film to a hot air drying tunnel, with the hot air temperature being 120 °C and the time being 20 min to obtain the high thermal conductivity wave-absorbing rubber sheet.

[0041] Example 3

[0042] The formula is shown in Table 1.

[0043] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.3%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 4 μm; the silicon carbide has a spherical structure with a D50 particle size of 40 μm; the phase change microcapsules are spherical phase change materials with a core / shell structure, a D50 particle size of 10 μm, and a phase change temperature of 45 °C (Hefei Xineng Phase Change New Material Technology Co., Ltd., PCM-45 (45 °C)); the diamond has an irregular polyhedron shape with a D50 particle size of 130 μm; the cross-linking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0044] The preparation process conditions are as follows: Weigh accurately according to the mass ratio of each component in Example 3 of Table 1. First, put vinyl silicone oil, iron carbonyl, silicon carbide, phase change microcapsules, diamond, and coupling agent into a double planetary mixer, and mix them at a high temperature of 180 °C for 40 min. After the material is cooled to room temperature, add other raw materials and mix for 40 min to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber compound mixture at room temperature for 40 min, and roll it into sheets through a rolling equipment. The rolling temperature is 60 °C and the thickness is 2 mm. Transfer the rolled film to a hot air drying tunnel, with the hot air temperature being 120 °C and the time being 20 min to obtain the high thermal conductivity wave-absorbing rubber sheet.

[0045] Example 4

[0046] The formula is shown in Table 1.

[0047] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.3%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 8 μm; the silicon carbide has a spherical structure with a D50 particle size of 60 μm; the phase change microcapsule is a spherical phase change material with a core / shell structure, a D50 particle size of 10 μm, and a phase change temperature of 45 °C (Hefei Xineng Phase Change New Materials Technology Co., Ltd., PCM-45 (45 °C)); the diamond has an irregular polyhedron shape with a D50 particle size of 130 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0048] The preparation process conditions are as follows: Weigh accurately according to the mass ratio of each component in Example 4 in Table 1. First, put the vinyl silicone oil, iron carbonyl, silicon carbide, phase change microcapsule, diamond, and coupling agent into a double planetary mixer and mix them at a high temperature of 180 °C for 40 min. After the material cools to room temperature, add other raw materials and mix for 40 min to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber mixture at room temperature for 40 min, and then roll it into a sheet through a rolling equipment at a rolling temperature of 60 °C and a thickness of 2 mm. Transfer the rolled sheet to a hot air drying tunnel with a hot air temperature of 120 °C for 20 min to obtain the high thermal conductivity wave-absorbing rubber sheet.

[0049] Comparative Example 1

[0050] The formula is shown in Table 1.

[0051] Compared with Example 1, the comparative example does not have diamond thermal conductive filler;

[0052] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.5%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 2 μm; the silicon carbide has a spherical structure with a D50 particle size of 40 μm; the phase change microcapsule is a spherical phase change material with a core / shell structure, a D50 particle size of 10 μm, and a phase change temperature of 45 °C (Hefei Xineng Phase Change New Materials Technology Co., Ltd., PCM-45 (45 °C)); the alumina has a spherical structure with a D50 particle size of 100 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 10 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0053] The preparation process conditions are as follows: Weigh precisely according to the mass ratio of each component in Comparative Example 1 of Table 1. First, put vinyl silicone oil, alumina, iron carbonyl, silicon carbide, phase change microcapsules, and coupling agent into a double planetary mixer, and mix them at a high temperature of 160 °C for 40 minutes. After the material cools to room temperature, add other raw materials and mix for 40 minutes to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber compound mixture at room temperature for 40 minutes, and roll it into a sheet through a rolling equipment. The rolling temperature is 30 °C and the thickness is 2 mm. Transfer the rolled sheet to a hot drying tunnel, with the hot air temperature at 120 °C for 20 minutes to obtain a thermally conductive and wave-absorbing rubber sheet.

[0054] Comparative Example 2

[0055] The formula is shown in Table 1.

[0056] Compared with Example 4, Comparative Example 2 does not have silicon carbide, phase change microcapsules, and diamond thermal conductive fillers;

[0057] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.3%; the iron carbonyl is lamellar iron carbonyl with a D50 particle size of 8 μm; the alumina has a spherical structure with a D50 particle size of 100 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is 3000 ppm silicone oil type (Zijun Chemical Industry (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0058] The preparation process conditions are as follows: Weigh precisely according to the mass ratio of each component in Comparative Example 2 of Table 1. First, put vinyl silicone oil, alumina, iron carbonyl, and coupling agent into a double planetary mixer, and mix them at a high temperature of 180 °C for 40 minutes. After the material cools to room temperature, add other raw materials and mix for 40 minutes to obtain a uniformly dispersed mixture. Vacuum degas the premixed rubber compound mixture at room temperature for 40 minutes, and roll it into a sheet through a rolling equipment. The rolling temperature is 60 °C and the thickness is 2 mm. Transfer the rolled sheet to a hot drying tunnel, with the hot air temperature at 120 °C for 20 minutes to obtain a thermally conductive and wave-absorbing rubber sheet.

[0059] Comparative Example 3

[0060] The formula is shown in Table 1.

[0061] Compared with Example 3, Comparative Example 3 does not have phase change microcapsule thermal conductive fillers;

[0062] The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa.s and a vinyl content of 0.3%; the carbonyl iron is lamellar carbonyl iron with a D50 particle size of 4 μm; the silicon carbide is a spherical structure with a D50 particle size of 40 μm; the diamond is an irregular polyhedron with a D50 particle size of 130 μm; the cross-linking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa.s and an active hydrogen content of 0.3%; the inhibitor is ethynyl cyclohexanol; and the platinum catalyst is a 3000 ppm silicone oil type (Zijun Chemical (Zhongshan) Co., Ltd., PT-3000 silicone oil type).

[0063] The preparation process conditions are as follows: According to the mass ratio of each component of comparative example 3 in Table 1, accurately weigh, first mix vinyl silicone oil, carbonyl iron, silicon carbide, diamond, and coupling agent in a double planetary mixer at a high temperature of 180°C for 40 minutes, and after the materials are cooled to room temperature, add other raw materials and mix for 40 minutes to obtain a uniformly dispersed mixture. The premixed rubber mixture is vacuum degassed at room temperature for 40 minutes, and calendered into sheets through a calendering device, with a calendering temperature of 60°C and a thickness of 2mm. The calendered rubber sheet is transferred to a hot drying tunnel, with a hot air temperature of 120°C for 20 minutes to obtain a heat-conducting and wave-absorbing rubber sheet.

[0064] Table 1 Formulas of Examples 1-4 and Comparative Examples 1-3 (by mass fraction)

[0065]

[0066]

[0067] The mechanical properties, wave absorbing properties and thermal conductivity of the heat-conductive and wave-absorbing rubber sheets prepared in Examples 1-4 and Comparative Examples 1-3 were tested. The test results are listed in Table 2.

[0068] Table 2 Sheet performance test results of Examples 1-4 and Comparative Examples 1-3

[0069]

[0070] It can be seen from Table 2 that the thermal conductivity of Comparative Example 3 is 5.7 W / mK, and the thermal conductivity of Examples 1-4 is greater than 4 W / mK, which are significantly better than the thermal conductivity of Comparative Example 1 and Comparative Example 2 without adding diamond, indicating that the thermal conductivity of the sheet filled with diamond is significantly better than the thermal conductivity of the sheet filled with alumina.

[0071] Compared with Example 1, Comparative Document 1 does not add diamond. The maximum absorption rate of Example 1 is -23dB, while the maximum absorption rate of Comparative Example 1 is -15dB, which indicates that the addition of diamond significantly improves the absorption effect and has excellent synergistic absorption effect.

[0072] Compared with Example 4, in Comparative Example 2, diamond, phase change microcapsules and silicon carbide thermal conductive fillers were not added. From the results of the microwave absorption performance test, the microwave absorption center frequency of Example 4 was around 4.5 GHz, in the C band (4 - 8 GHz). The microwave absorption center frequency of Comparative Example 2 was around 6.3 GHz, in the C band (4 - 8 GHz), and the maximum microwave absorption rate was -19 dB. It shows that after introducing the carbon-based microwave absorption filler, the microwave absorption center frequency shifted to the lower frequency by about 2 GHz. In addition, it can be seen from Examples 1 - 4 that as the addition amount of carbonyl iron gradually increases, the center frequency of the thermal conductive and microwave absorption rubber sheet shifts to the lower frequency. The microwave absorption center frequency of the sheet in Example 1 was around 8.4 GHz, in the X band (8 - 12 GHz), the microwave absorption center frequency of the sheet in Example 2 was 7.9 GHz, in the C band (4 - 8 GHz), the microwave absorption center frequency of the sheet in Example 3 was 7.3 GHz, in the C band (4 - 8 GHz), and the microwave absorption center frequency of the sheet in Example 4 was 4.5 GHz, in the C band (4 - 8 GHz), and the maximum microwave absorption rates were all less than -20 dB, all showing excellent microwave absorption effects and synergistic microwave absorption effects, and indicating that the microwave absorption center frequency range can be adjusted by adjusting the addition amount of carbonyl iron.

[0073] Compared with Example 3, in Comparative Example 3, phase change microcapsules were not added. From the results of the mechanical property test, the tensile strength of Comparative Example 3 was 0.12 MPa and the elongation at break was 42%; the tensile strength of Example 3 was 0.23 MPa and the elongation at break was 69%; it shows that adding phase change microcapsules can improve the mechanical properties of the sheet. In addition, it can be seen from Examples 1 - 4 that the tensile strengths were all greater than 0.19 MPa and the elongations at break were all greater than 61%, which were significantly better than the mechanical properties of Comparative Example 1 and Comparative Example 2, and the mechanical properties of Example 2 were the best, indicating that appropriately increasing the filling amount of phase change microcapsules can further improve the mechanical properties of the sheet.

Claims

1. A highly thermally conductive wave-absorbing rubber sheet, characterized in that, The raw materials for preparing the high thermal conductivity wave-absorbing rubber sheet are as follows by mass: 100 parts of vinyl silicone oil, 500 parts of lamellar carbonyl iron, 200 parts of silicon carbide, 100 parts of phase change microcapsules, 500 parts of diamond, 4.5 parts of crosslinking agent, 0.4 part of inhibitor, 0.6 part of platinum catalyst, and 4 parts of coupling agent; The preparation method of the high thermal conductivity wave-absorbing rubber sheet is as follows: First, vinyl silicone oil, lamellar carbonyl iron, silicon carbide, phase change microcapsules, diamond, and coupling agent are mixed in a double planetary mixer at a high temperature of 180 °C for 40 min. After the material is cooled to room temperature, other raw materials are added and mixed for 40 min to obtain a uniformly dispersed mixture; the premixed rubber compound mixture is degassed under vacuum at room temperature for 40 min, and then rolled into sheets through a rolling equipment at a rolling temperature of 60 °C and a thickness of 2 mm; the rolled sheet is transferred to a hot air drying tunnel, and the hot air temperature is 120 °C for 20 min to obtain the high thermal conductivity wave-absorbing rubber sheet; The vinyl silicone oil used is vinyl-terminated polydimethylsiloxane with a viscosity of 100 mPa·s and a vinyl content of 0.3%; the D50 particle size of the lamellar carbonyl iron is 8 μm; the silicon carbide has a spherical structure with a D50 particle size of 60 μm; the phase change microcapsules are spherical phase change materials with a core / shell structure, the D50 particle size is 10 μm, and the phase change temperature is 45 °C; the diamond has an irregular polyhedron shape with a D50 particle size of 130 μm; the crosslinking agent is hydrogen-terminated polydimethylsiloxane with a viscosity of 15 mPa·s and an active hydrogen content of 0.3%; the inhibitor is ethynylcyclohexanol; the platinum catalyst is a 3000 ppm silicone oil type.

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