Phase-change thermal interface material and preparation method therefor

Abstract

Provided in the present invention are a phase-change thermal interface material and a preparation method therefor. The phase-change thermal interface material comprises the following component raw materials in parts by mass: 0.1-99.9 parts of an olefin material, 0.1-99.9 parts of a graftable high-molecular prepolymer, 0.1-99.9 parts of a cross-linked high-molecular prepolymer, 0.1-99.9 parts of a heat-conducting filler, and 0.1-1 part of a catalyst. For the phase-change thermal interface material of the present invention, under the condition of the parts of fillers being the same, the invented composite thermal interface material with phase-change characteristics has a thermal conductivity improved by 28.6% and a thermal contact resistance reduced by 46.1% compared with those of a composite thermal interface material of the same type but without phase-change characteristics. The preparation method is simple and is suitable for industrial production.

Description

Phase change thermal interface material and preparation method thereof Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a phase-change thermal interface material and a preparation method thereof. Background Art

[0002] Thermal interface materials play a role as a "thermal bridge" in electronic devices such as packaged chips and equipment thermal management technology. They can fill the gap between the heat source and various thermal management components and establish a heat transport bridge, allowing the packaged chip to dissipate heat in a timely manner, ensuring its efficient operation and extending its service life. The key factor in measuring the thermal transport efficiency of thermal interface materials is the effective total thermal resistance of the material, which is expressed as follows: R total =R contact1 +R contact2 +d / k

[0003] where R total is the effective total thermal resistance; R contact1,2 is the interfacial contact thermal resistance between the thermal interface material and the contacting solid; k is the intrinsic thermal conductivity of the thermal interface material; and d is the thickness of the thermal interface material. As can be seen from the equation, improving the material's inherent thermal conductivity (k) and reducing the material's contact thermal resistance are key to improving the thermal transport efficiency of the thermal interface material, that is, enhancing its thermal conductivity. In recent years, many polymer composites have been designed as thermal interface materials to increase thermal conductivity and thereby reduce thermal resistance. These thermal interface materials employ strategies such as increasing filler content to form a three-dimensional thermal conductive pathway network, filler hybridization, and surface modification. In fact, an ideal thermal interface material must not only possess extremely strong thermal conductivity, but also excellent shape adaptability and interface compatibility to ensure perfect material fit at the interface, reduce interfacial contact thermal resistance, and enable efficient cross-boundary heat transport.

[0004] An effective way to improve the interfacial compatibility of thermal interface materials is to reduce the material modulus. Phase change materials can be used as the matrix of thermal interface materials because of their significant change in modulus before and after the phase change. When the thermal interface material is exposed to high temperatures, the matrix undergoes a phase change, the modulus decreases, and the interfacial compatibility is enhanced under the same pressure, thereby improving heat conduction at the interface. However, traditional phase change materials undergo a solid-liquid phase transition, which can easily lead to liquefaction and leakage of the phase change material during application, thereby affecting the material's thermal conductivity and even damaging electronic devices. Therefore, preventing material liquefaction and leakage is a huge challenge in the development of phase change thermal interface materials.

[0005] Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a phase change thermal interface material and a preparation method thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a phase-change thermal interface material, comprising the following raw materials, calculated by mass: 0.1 to 99.9 parts of an olefin material, 0.1 to 99.9 parts of a graftable polymer prepolymer, 0.1 to 99.9 parts of a cross-linked polymer prepolymer, 0.1 to 99.9 parts of a thermally conductive filler, and 0.1 to 1 part of a catalyst.

[0009] Furthermore, the thermal conductivity of the phase change thermal interface material is 0.1W / mK to 100.0W / mK, and the contact heat group is 10 -7 m 2 K / W~10 -4 m 2 K / W.

[0010] Furthermore, the olefin material is any unsaturated olefin with a single-terminal carbon-carbon double bond and phase change properties, including hexadecene, octadecene, and eicosene.

[0011] Furthermore, the graftable high molecular prepolymer is a hydrogenated silicone oil that can undergo addition reaction with olefin materials.

[0012] Furthermore, the cross-linked high molecular prepolymer is a polydimethylsiloxane prepolymer.

[0013] Furthermore, the thermally conductive filler is an inorganic material such as alumina, aluminum, zinc oxide, aluminum hydroxide, magnesium hydroxide, or a carbon-based material such as graphene, expanded graphite, carbon nanotubes, and one or more new fillers modified from the inorganic materials and / or carbon-based materials.

[0014] Furthermore, the particle size of the thermally conductive filler is between 0.001 μm and 100 μm; the shape of the thermally conductive filler is one or more of spherical, ellipsoidal, lamellar, tubular, and long rod-shaped; the thermally conductive filler is arranged in the phase change thermal interface material in one or more of the following arrangements: vertical arrangement, stacking, paving, and uniform dispersion.

[0015] Furthermore, the catalyst is at least one of chloroplatinic acid, chloroplatinic acid-isopropyl alcohol complex, and chloroplatinic acid-divinyltetramethyldisiloxane complex.

[0016] The present invention also provides a method for preparing the above-mentioned phase change thermal interface material, which includes: uniformly mixing and stirring olefin materials, graftable polymer prepolymers, cross-linked polymer prepolymers, thermal conductive fillers, and catalysts to obtain phase change thermal interface materials; wherein the equipment used for the uniform mixing and stirring is a planetary mixer, a kneader, or a high-speed mixer.

[0017] Furthermore, the method also includes: heating and curing the phase change thermal interface material to form a gasket, or forming a thermal conductive gel without heating and curing; wherein the shape of the gasket is one or more of circular, elliptical, heart-shaped, star-shaped, diamond-shaped, rectangular, square, and irregular polygonal; the thickness of the gasket is 0.1μm to 5000μm.

[0018] Compared with the existing technology, the technical solution provided by the present invention has at least the following advantages:

[0019] The present invention provides a phase-change thermal interface material and its preparation method. Compared to similar materials without phase-change properties, the invented composite thermal interface material with phase-change properties has a 28.6% higher thermal conductivity and a 46.1% lower contact thermal resistance, given the same filler content. The preparation method is simple and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are exemplarily described by the pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0021] FIG1 is a graph showing the tensile strength and elongation at break of Examples 1 to 4 of the present invention;

[0022] FIG2 is a graph showing the leakage rate test results of Examples 1 to 4 of the present invention;

[0023] FIG3 is a graph showing the material modulus test results of Examples 1 to 4 of the present invention;

[0024] FIG4 is a diagram showing the hardness test results of Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0025] The present invention aims to provide a novel thermal interface material that exhibits phase change properties and a low modulus after the phase change, thereby addressing issues such as poor interfacial compatibility and high contact thermal resistance in thermal conductivity applications. Currently, most phase change materials exhibit solid-to-liquid phase change properties, which can lead to liquefaction and leakage during application. Therefore, the proposed thermal interface material should exhibit solid-to-solid phase change properties to prevent leakage after the phase change.

[0026] By grafting olefin molecular chains with side chain hydrogenated siloxane as a cross-linked prepolymer, the cross-linked polymer is made to have the property of solid-solid phase change; by compounding with inorganic fillers, a phase change thermal interface material with phase change characteristics, uniform dispersion of fillers and enhanced thermal conductivity is prepared.

[0027] The present invention provides a phase-change thermal interface material, comprising the following raw materials, calculated by mass: 0.1 to 99.9 parts of an olefin material, 0.1 to 99.9 parts of a graftable polymer prepolymer, 0.1 to 99.9 parts of a cross-linked polymer prepolymer, 0.1 to 99.9 parts of a thermally conductive filler, and 0.1 to 1 part of a catalyst.

[0028] The present invention also provides a method for preparing the above-mentioned phase change thermal interface material, which includes: uniformly mixing and stirring olefin materials, graftable polymer prepolymers, cross-linked polymer prepolymers, thermal conductive fillers, and catalysts to obtain phase change thermal interface materials; wherein the equipment used for the uniform mixing and stirring is a planetary mixer, a kneader, or a high-speed mixer.

[0029] The present invention will be described in detail below in conjunction with specific embodiments. It should be noted that, in the following embodiments, units "parts" are "parts by mass" unless otherwise specified.

[0030] Example 1

[0031] (A) 4.4 parts by mass of side chain hydrogenated silicone oil and 11.6 parts of hexadecene were subjected to an addition reaction to obtain 16 parts of grafted hexadecene side chain hydrogenated silicone oil for further use. The synthesis operation is well known and need not be described in detail.

[0032] (B) 80 parts of thermally conductive filler, 16 parts of grafted hexadecene side chain hydrogenated silicone oil, and 4 parts of polydimethylsiloxane prepolymer are added to a high-speed mixer and stirred at room temperature at high speed. The specific parameters can be set to stirring at 1000 rpm for 60 seconds, then stirring at 1200 rpm for 45 seconds, then stirring at 1500 rpm for 30 seconds, and finally stirring at 1800 rpm for 15 seconds.

[0033] (C) After thorough stirring, 0.1 parts of chloroplatinic acid-divinyltetramethyldisiloxane complex was added.

[0034] (D) Stirring was continued at 1000 rpm for 45 seconds, 1200 rpm for 30 seconds, and 1500 rpm for 15 seconds at 20°C and vacuum degree -90.0 kPa.

[0035] (E) The above mixture is taken out and rolled into different thicknesses.

[0036] (F) After heating and curing, test and use.

[0037] Example 2

[0038] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 80 parts by mass of thermal conductive filler, 14 parts of grafted hexadecene side chain hydrogenated silicone oil (3.8 parts of side chain hydrogenated silicone oil, 10.2 parts of hexadecene), and 6 parts of polydimethylsiloxane prepolymer.

[0039] Example 3

[0040] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 80 parts by mass of thermal conductive filler, 12 parts of grafted hexadecene side chain hydrogenated silicone oil (3.3 parts of side chain hydrogenated silicone oil, 8.7 parts of hexadecene), and 8 parts of polydimethylsiloxane prepolymer.

[0041] Example 4

[0042] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 80 parts by mass of thermal conductive filler, 10 parts of grafted hexadecene side chain hydrogenated silicone oil (2.7 parts of side chain hydrogenated silicone oil, 7.3 parts of hexadecene), and 10 parts of polydimethylsiloxane prepolymer.

[0043] Example 5

[0044] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 75 parts by mass of thermal conductive filler, 20 parts of grafted hexadecene side chain hydrogenated silicone oil (5.5 parts of side chain hydrogenated silicone oil, 14.5 parts of hexadecene), and 5 parts of polydimethylsiloxane prepolymer.

[0045] Example 6

[0046] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 85 parts by mass of thermal conductive filler, 12 parts of grafted hexadecene side chain hydrogenated silicone oil (3.3 parts of side chain hydrogenated silicone oil, 8.7 parts of hexadecene), and 3 parts of polydimethylsiloxane prepolymer.

[0047] Example 7

[0048] The operation is basically the same as that in Example 1, except that the number of synthetic materials is changed to 90 parts by mass of thermal conductive filler, 8 parts of grafted hexadecene side chain hydrogenated silicone oil (2.7 parts of side chain hydrogenated silicone oil, 5.3 parts of hexadecene), and 2 parts of polydimethylsiloxane prepolymer.

[0049] Comparative Example 1

[0050] The operation is basically the same as that of Example 1, except that the proportion of the synthetic material is changed to 80 parts by mass of thermal conductive filler and 20 parts by mass of polydimethylsiloxane prepolymer.

[0051] (1) Thermal conductivity test of thermal interface materials:

[0052] The material's intrinsic thermal conductivity and contact thermal resistance were tested using a Ruiling thermal conductivity tester (LW9389). The test was based on ASTM D 5470, a well-known standard that is unnecessary to elaborate on here.

[0053] According to the above method, the thermal conductivity and contact thermal resistance test results of the thermal interface materials obtained in Examples 1 to 4 and Comparative Example 1 are shown in the following table:

[0054] According to the above method, the thermal conductivity and contact thermal resistance test results of the thermal interface materials obtained in Examples 1, 5 to 7 are shown in the following table:

[0055] (2) Material mechanical strength test:

[0056] The material was tested at both high and low temperatures (room temperature and 75°C) using a universal tensile tester (Shimadzu, Japan, model AG-X plus 10N-10kN). The test method and technology are well known and need not be described here. The tensile rate was set at 3 mm / min.

[0057] The tensile strength and elongation at break of Examples 1 to 4 were tested according to the above method, and the raw data of the results are shown in FIG1 . In particular, FIG1 (a) shows the test results of the tensile strength and elongation at break under the normal temperature test state, and FIG1 (b) shows the test results of the tensile strength and elongation at break under the high temperature test state. The test summary results are shown in the following table:

[0058] Figure 1 shows the stress-strain curves for Examples 1-4 at room temperature and 75°C. At room temperature, the tensile strength of the samples increased with increasing grafted hexadecene content. Simultaneously, due to the higher inherent strength and lower deformation of crystalline hexadecene, the elongation at break decreased. At 75°C, both tensile strength and elongation were negatively correlated with the grafted hexadecene content. As the temperature increased, the hexadecene transitioned from crystalline to amorphous, resulting in lower tensile strength.

[0059] (3) Leakage rate test:

[0060] The leakage rate is measured by placing a sample with an initial mass of M0 on a filter paper in an oven maintained at 60°C. After one hour, the sample is removed and weighed using an analytical balance, with the filter paper replaced after each weighing. The mass of the sample after heating n times in the oven is defined as M n The formula for calculating the material leakage rate is as follows: L=(M0-M n ) / M0×100%

[0061] The leakage rate test results of Examples 1 to 4 tested according to the above method are shown in FIG2 , and the test summary results are shown in the following table:

[0062] As shown in Figure 2, Examples 1-4 exhibited extremely low leakage rates. Furthermore, since the leakage rate did not increase over time, this indicates that the leaked liquid was polydimethylsiloxane prepolymer monomer, which does not participate in the crosslinking process. This indirectly confirms that the material exhibits solid-solid phase transition properties and is leak-proof.

[0063] (3) Material modulus test:

[0064] The storage modulus of the material was tested using a dynamic mechanical analyzer (DMA) in a test temperature range of 0 to 80°C and a heating rate of 2°C per minute.

[0065] The changes in the modulus of Examples 1 to 4 as the temperature rises were tested according to the above method. The material modulus test results are shown in FIG3 , and the test results are summarized in the following table:

[0066] As shown in Figure 3, the storage modulus of Examples 1–4 decreases from 4.770–6.185 MPa at room temperature to 1.305–0.415 MPa at elevated temperatures, respectively. This is because crystallized hexadecene has a higher modulus at room temperature. At elevated temperatures, hexadecene transforms from a crystalline state to an amorphous state, shifting the bulk of the material's modulus from hexadecene to the crosslinked polydimethylsiloxane network. Because Example 1 has the highest hexadecene content, crystallization is greatest at room temperature, resulting in the highest modulus, while the modulus is lowest at elevated temperatures.

[0067] The cross-linked networks in Examples 1 to 4 at high temperature are mainly contributed by the polydimethylsiloxane prepolymer.

[0068] (4) Material hardness test:

[0069] The hardness of the material was tested using a Shore hardness tester at room temperature and 75°C.

[0070] The hardness test results of Examples 1 to 4 tested according to the above method are shown in FIG4 , and the test summary results are shown in the following table:

[0071] As can be seen from Figure 4, the hardness of Examples 1 to 4 decreases from 93.6-96.9 at room temperature to 76-90.8 at high temperature. As the temperature changes, the grafted hexadecene changes from a crystalline state to an amorphous state, causing a significant change in hardness.

[0072] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be subject to the scope defined in the claims.

Claims

1. A phase change thermal interface material, characterized in that: The raw materials include the following components in parts by mass: 0.1 to 99.9 parts of olefin materials, 0.1 to 99.9 parts of graftable polymer prepolymers, 0.1 to 99.9 parts of cross-linked polymer prepolymers, 0.1 to 99.9 parts of thermal conductive fillers, and 0.1 to 1 parts of catalysts.

2. The phase change thermal interface material according to claim 1, characterized in that: The thermal conductivity of the phase change thermal interface material is 0.1W / mK~100.0W / mK, and the contact heat group is 10 -7 m 2 K / W~10 -4 m 2 K / W.

3. The phase change thermal interface material according to claim 1, characterized in that: The olefin material is all unsaturated olefins with single-end carbon-carbon double bonds and phase change characteristics, including hexadecene, octadecene and eicosene.

4. The phase change thermal interface material according to claim 1, characterized in that: The graftable high molecular prepolymer is hydrogen-containing silicone oil which can undergo addition reaction with olefin materials.

5. The phase change thermal interface material according to claim 1, characterized in that: The cross-linked high molecular prepolymer is a polydimethylsiloxane prepolymer.

6. The phase change thermal interface material according to claim 1, characterized in that: The thermal conductive filler is an inorganic material of alumina, aluminum, zinc oxide, aluminum hydroxide, magnesium hydroxide, or a carbon-based material of graphene, expanded graphite, carbon nanotubes, and one or more new fillers modified from the inorganic material and / or carbon-based material.

7. The phase change thermal interface material according to claim 6, characterized in that: The particle size of the thermal conductive filler is between 0.001 μm and 100 μm; The shape of the thermal conductive filler is one or more of spherical, ellipsoidal, sheet-like, tubular, and long rod-like; The thermal conductive filler is arranged in the phase change thermal interface material in one or more arrangements of vertical arrangement, stacking, paving, and uniform dispersion.

8. The phase change thermal interface material according to claim 1, characterized in that: The catalyst is at least one of chloroplatinic acid, chloroplatinic acid-isopropanol complex, and chloroplatinic acid-divinyltetramethyldisiloxane complex.

9. The method for preparing a phase change thermal interface material according to any one of claims 1 to 8, characterized in that: The method comprises: uniformly mixing and stirring olefin materials, graftable polymer prepolymers, cross-linked polymer prepolymers, thermal conductive fillers, and catalysts to obtain phase-change thermal interface materials; Wherein, the equipment used for the uniform mixing and stirring is a planetary mixer, a kneader or a high-speed mixing and stirring machine.

10. The method for preparing a phase change thermal interface material according to claim 9, characterized in that: The method further comprises: heating and curing the phase change thermal interface material to form a gasket, or not heating and curing to form a thermally conductive gel; The shape of the gasket is one or more of a circle, an ellipse, a heart, a star, a diamond, a rectangle, a square, and an irregular polygon; The thickness of the gasket is 0.1 μm to 5000 μm.

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