Solvent-free rubber-based adhesive with high thermal conductivity and preparation method of solvent-free rubber-based adhesive

Abstract

The invention discloses a preparation method of a high-thermal-conductivity solvent-free rubber-based adhesive, which is characterized in that the adhesive takes rubber as a matrix, takes terpene resin as a tackifier, and takes tannic acid coated zinc oxide and carbon nanotubes to synergistically construct a heterogeneous thermal conductive network and a peroxide cross-linking agent to synergistically enhance a cross-linked structure. The preparation method comprises the following steps: firstly, uniformly, compactly and firmly coating zinc oxide (ZnO) particles on the surfaces of carbon nanotubes (CNTs) by taking tannic acid (TA) as an interface adhesive under the assistance of ultrasonic dispersion force to form a unique core (CNTs)-shell (ZnO) heterostructure heat-conducting filler (TA (at) CNTs (at) ZnO); then, the heterostructure filler, rubber and terpene resin are subjected to mixing and crosslinking processes to prepare the high-thermal-conductivity composite material. In the hot press molding stage, the core-shell filler with one-dimensional characteristics is directionally arranged under the action of pressure, a continuous three-dimensional heat-conducting network is efficiently constructed, directional transfer of heat is greatly promoted, and meanwhile, terpene resin and tannic acid synergistically play an adhesion role. The rubber-based adhesive has excellent elastic recovery rate, heat-conducting property and bonding strength, is simple and convenient in preparation method, is solvent-free, is environment-friendly, and is suitable for the fields of heat dissipation of electronic devices, thermal interface materials and the like.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive rubber and adhesives, specifically to a high thermal conductivity solvent-free rubber-based adhesive and its preparation method. Background Technology

[0002] Driven by Moore's Law, the size of semiconductor chips has shrunk from tens of micrometers to a few nanometers over the past few decades. While this miniaturization brings high power density, it also presents significant heat dissipation challenges. If heat cannot be dissipated effectively and promptly, it will lead to performance degradation or even damage to the device. Therefore, the heat dissipation efficiency of power devices is crucial. In recent years, thermal interface bonding materials, due to their unique soft, elastic, and adhesive properties, can effectively eliminate air gaps between heat sources and heat sinks, exhibiting excellent auxiliary heat dissipation capabilities and thus becoming a research hotspot.

[0003] Traditional thermal interface adhesives, such as silicone grease and epoxy resins, while possessing some thermal conductivity, often suffer from poor elasticity, are prone to aging, and contain harmful solvents, making them unsuitable for meeting the requirements of modern electronic devices for flexibility, environmental friendliness, and high reliability. Rubber materials, possessing excellent elasticity, thermal conductivity, and being solvent-free, are ideal candidates for non-silicone-based thermal interface materials. However, the thermal conductivity of rubber materials is generally low (often below 0.5 W / (m·K)). To improve thermal conductivity, a high proportion of thermally conductive fillers (such as alumina, boron nitride, and carbon nanotubes) is usually added, but excessive fillers can lead to brittleness, decreased elasticity, and processing difficulties. Furthermore, traditional adhesives often employ solvent-based preparation processes, using large amounts of organic solvents, resulting in volatile organic compound (VOC) emissions, which is inconsistent with green manufacturing trends. Currently, reported natural rubber and styrene-butadiene rubber-based adhesives still use large amounts of organic solvents or emulsion solvent systems, while completely solvent-free solid-phase rubber-based adhesive systems remain scarce. Therefore, developing a rubber-based adhesive that combines high thermal conductivity, strong adhesion, and solvent-free properties has significant research value and application prospects. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a high thermal conductivity solvent-free rubber-based adhesive. This method utilizes tannic acid-Fe... 3+ Coordination-modified carbon nanotubes significantly improve the filler-matrix interface compatibility; the use of natural terpene resin as a tackifier achieves high bond strength under solvent-free conditions; and the combination with rubber crosslinking network design achieves a synergistic improvement in elasticity and thermal conductivity. This invention features a simple, solvent-free preparation method that can be achieved using conventional rubber processing methods, making it suitable for the stringent requirements of efficient heat dissipation and reliable interface contact in the thermal management field of high-end electronic devices.

[0005] The objective of this invention is achieved by the following technical solution, wherein the raw material fractions are all parts by mass unless otherwise specified.

[0006] The main raw materials of a high thermal conductivity solvent-free rubber-based adhesive are composed of the following components: 40-90 parts of rubber 10-60 parts of terpene resin Tannic acid 0.6-6 parts 0.5-5 parts carbon nanotubes 0.5-5 parts zinc oxide Peroxide crosslinking agent 0.01-0.05 parts Crosslinking agent 0.01-0.03 parts The rubber is any one or a mixture of two of EPDM rubber, natural rubber, and butadiene rubber. The terpene resin is a natural terpene resin with a softening point of 80~120℃. It is environmentally friendly and non-toxic. Its molecular structure contains unsaturated bonds and polar groups, which can enhance compatibility with rubber and provide a long-lasting tackifying effect. The peroxide crosslinking agent is any one of cumene peroxide, benzoyl peroxide, and 1,4-bis-tert-butylperoxycumene. The crosslinking agent is any one of triallyl cyanurate, zinc methacrylate, zinc diethyldithiocarbamate, and N-cyclohexyl-2-benzothiazole sulfenamide.

[0007] The tannic acid is obtained through Fe 3+ Coordination modifies the surface of carbon nanotubes, forming a tannic acid-Fe-CNT heterostructure; The zinc oxide is further coated on the surface of the above structure to form a "core-shell" heterogeneous thermally conductive filler. In the system, the zinc oxide serves as both a thermally conductive filler and a coating layer on the tannic acid-Fe-CNT surface, further improving the interfacial heat transfer efficiency.

[0008] A method for preparing a high thermal conductivity solvent-free rubber-based adhesive includes the following steps: S1: Preparation of heterogeneous thermally conductive fillers Weigh 0.5-5 parts of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 0.6-6 parts of tannic acid, stir evenly, and pour into the dispersion; add FeCl3·6H2O dissolved in water, pour into the mixture, and react in a water bath at 50-70℃ for 5-15 min; then weigh 0.5-5 parts of ZnO and pour into the mixture, and under ultrasonic dispersion, make it completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO), which is ready for use.

[0009] S2: Preparation of rubber adhesive Mix 10-60 parts of terpene resin and 40-90 parts of rubber on a two-roll mill, then add stearic acid, the heterogeneous thermally conductive filler prepared in S1, 0.01-0.05 parts of peroxide crosslinking agent, and 0.01-0.03 parts of co-crosslinking agent in sequence, and mix evenly. Place the mixed rubber in a mold and hot-press it at 150-180℃ and 5-15 MPa for 10-30 min to obtain a thermally conductive rubber-based adhesive.

[0010] Furthermore, in step S1, the molar ratio of FeCl3·6H2O to tannic acid is 1:5 to 1:10. Tannic acid reacts with Fe through its catechol structure. 3+ Stable coordination bonds are formed and adsorbed on the surface of carbon nanotubes to form a tannic acid-Fe-CNT interface modification layer, which greatly enhances the interfacial bonding force between the filler and the rubber.

[0011] The above technical solution can achieve the following beneficial effects: Through tannic acid-Fe 3+ Coordination modification of carbon nanotube surfaces forms a stable interfacial bonding layer, significantly reducing the interfacial thermal resistance between the filler and the rubber matrix, and significantly improving the efficiency of thermally conductive network construction. Zinc oxide forms a coating structure on the tannic acid-Fe-CNT surface, further enhancing the phonon transport path and achieving heterogeneous synergistic thermal conduction of "CNT-ZnO". The catechol structure in the tannic acid molecule enhances the filler-rubber interfacial bonding through multiple interactions such as coordination bonds and hydrogen bonds, improving stress transfer efficiency. Natural terpene resin molecules contain unsaturated bonds and polar groups, exhibiting good compatibility with rubber and providing a durable, environmentally friendly tackifying effect with high bonding strength. The entire preparation process is solvent-free, and the final product has no VOC emissions, conforming to the trend of green manufacturing. This invention utilizes the "tannic acid-Fe 3+ The triple technological innovation of “interface modification”, “environmentally friendly tackification with terpene resin” and “synergistic thermal conduction with heterogeneous fillers” has successfully solved the technical bottleneck of traditional rubber-based adhesives in achieving both high thermal conductivity and bonding strength and environmental friendliness. It provides an environmentally friendly new generation of thermal interface material solution for fields such as electronic heat dissipation, thermal management of new energy vehicle batteries and flexible wearable devices. Attached Figure Description

[0012] Figure 1 The morphology and structure of core-shell heterogeneous thermally conductive fillers.

[0013] Figure 2 This describes the interfacial bonding morphology between the thermally conductive filler and the matrix in a rubber-based adhesive.

[0014] Figure 3 This is a schematic diagram showing the adhesion of rubber-based adhesives to different substrates. Detailed Implementation

[0015] The present invention will be further described below through specific embodiments. It should be noted that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make non-essential improvements and adjustments to the present invention based on the above content. Example 1

[0016] Weigh 0.5 parts of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 0.6 parts of tannic acid, stir evenly, and pour into the dispersion; add 0.2 parts of FeCl3·6H2O dissolved in water, pour into the mixture, and react in a 50℃ water bath for 5 min; then weigh 0.5 parts of ZnO and pour into the mixture, and under ultrasonic dispersion, make it completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO).

[0017] Ten parts of terpene resin and 90 parts of EPDM rubber were mixed on a two-roll mill. Then, 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.03 parts of dicumyl peroxide, and 0.01 parts of triallyl cyanurate were added sequentially and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 150°C and 10 MPa for 10 min to obtain a thermally conductive rubber-based adhesive. Example 2

[0018] Weigh 1 part of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 1 part of tannic acid, stir evenly and pour into the dispersion; add 0.3 parts of FeCl3·6H2O dissolved in water, pour into the mixture, and react in a 50℃ water bath for 5 min; then weigh 0.5 parts of ZnO and pour into the mixture, and ultrasonically disperse to completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO).

[0019] 20 parts of terpene resin and 80 parts of EPDM rubber were mixed on a two-roll mill. Then, 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.03 parts of dicumyl peroxide, and 0.01 parts of triallyl cyanurate were added sequentially and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 150°C and 10 MPa for 10 min to obtain a thermally conductive rubber-based adhesive. Example 3

[0020] Weigh 2 parts of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 2 parts of tannic acid, stir evenly and pour into the dispersion; add 1 part of FeCl3·6H2O dissolved in water, pour into the mixture, and react in a 60℃ water bath for 8 min; then weigh 2 parts of ZnO and pour into the mixture, and ultrasonically disperse to completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO).

[0021] 30 parts of terpene resin and 70 parts of natural rubber were mixed on a two-roll mill. Then, 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.02 parts of benzoyl peroxide, and 0.01 parts of zinc methacrylate were added sequentially and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 160°C and 10 MPa for 12 min to obtain a thermally conductive rubber-based adhesive. Example 4

[0022] Weigh 3 parts of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 4 parts of tannic acid, stir evenly and pour into the dispersion; add 1 part of FeCl3·6H2O dissolved in water, pour into the mixture, and react in a 70℃ water bath for 12 min; then weigh 3 parts of ZnO and pour into the mixture, and ultrasonically disperse to completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO).

[0023] 40 parts of terpene resin and 60 parts of cis-butadiene rubber were mixed on a two-roll mill. Then, 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.04 parts of 1,4-di-tert-butylperoxyisopropylbenzene, and 0.02 parts of N-cyclohexyl-2-benzothiazole sulfenamide were added sequentially and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 170°C and 15 MPa for 15 min to obtain a thermally conductive rubber-based adhesive.

[0024] Comparative Example 1 Weigh 1 part of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 1 part of tannic acid, stir evenly and pour into the dispersion; add 0.3 parts of FeCl3·6H2O dissolved in water, pour into the mixture, and react in a 50℃ water bath for 5 min; then weigh 0.5 parts of ZnO and pour into the mixture, and ultrasonically disperse to completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler (TA@CNTs@ZnO).

[0025] 100 parts of EPDM rubber were mixed on a two-roll mill, and 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.03 parts of dicumyl peroxide, and 0.01 parts of triallyl cyanurate were added in sequence and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 150°C and 10 MPa for 10 min to obtain a thermally conductive rubber-based adhesive.

[0026] Comparative Example 2 Weigh 1 part of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; then weigh 0.5 parts of ZnO and pour it into the mixture, and ultrasonically disperse it to completely coat the carbon nanotubes. Filter and dry at 50℃ to obtain heterogeneous thermally conductive filler (CNTs@ZnO).

[0027] 20 parts of terpene resin and 80 parts of EPDM rubber were mixed on a two-roll mill. Then, 1 part of stearic acid, the above-mentioned heterogeneous thermally conductive filler, 0.03 parts of dicumyl peroxide, and 0.01 parts of triallyl cyanurate were added sequentially and mixed evenly. The mixed rubber was placed in a mold and hot-pressed at 150°C and 10 MPa for 10 min to obtain a thermally conductive rubber-based adhesive.

[0028] The test results are shown in Table 1.

[0029] Table 1 Performance Test Results

[0030] The results in Table 1 show that: The rubber-based adhesive prepared by this invention exhibits excellent thermal conductivity, mechanical properties, and bonding strength, demonstrating that terpene resin and tannic acid significantly enhance the overall performance of the rubber adhesive, and that the bonding strength increases with increasing terpene resin content. Comparative Examples 2 and 1 and 2 show that adding terpene resin or tannic acid significantly improves the mechanical strength and bonding strength of the composite material, proving the effectiveness of the method of this invention.

[0031] The above embodiments have described the specific content of the present invention in detail, but the present invention is not limited to the embodiments described. Those skilled in the art can make equivalent substitutions, all of which should be covered within the protection scope of the present invention.

Claims

1. A high thermal conductivity solvent-free rubber-based adhesive, characterized in that... The main raw materials of this rubber-based adhesive material are composed of the following components, in parts by mass: 40-90 parts of raw rubber 10-60 parts of terpene resin Tannic acid 0.6-6 parts 0.5-5 parts carbon nanotubes 0.5-5 parts zinc oxide Peroxide crosslinking agent 0.01-0.05 parts Crosslinking agent 0.01-0.03 parts The raw rubber is any one or a mixture of two of EPDM rubber, natural rubber, and butadiene rubber. The terpene resin is a natural terpene resin with a softening point of 80~120℃; The peroxide crosslinking agent is any one of cumene peroxide, benzoyl peroxide, and 1,4-bis-tert-butylperoxycumene. The crosslinking agent is any one of triallyl cyanurate, zinc methacrylate, zinc diethyldithiocarbamate, and N-cyclohexyl-2-benzothiazole sulfenamide.

2. The high thermal conductivity solvent-free rubber-based adhesive according to claim 1, characterized in that, The tannic acid is obtained through Fe 3+ Coordination modifies the surface of carbon nanotubes, forming a tannic acid-Fe-CNT heterostructure; The zinc oxide is further coated on the surface of the above structure to form a "core-shell" heterogeneous thermally conductive filler.

3. A method for preparing a high thermal conductivity solvent-free rubber-based adhesive as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Preparation of heterogeneous thermally conductive fillers Weigh 0.5-5 parts of carbon nanotubes into a beaker, add 100 parts of distilled water, and ultrasonically disperse for 1 h; take 0.6-6 parts of tannic acid, stir evenly, and pour into the dispersion; add FeCl3·6H2O dissolved in water, pour into the mixture, and react in a water bath at 50-70℃ for 5-15 min; then weigh 0.5-5 parts of ZnO and pour into the mixture, and under ultrasonic dispersion, completely coat the carbon nanotubes, filter, and dry at 50℃ to obtain heterogeneous thermally conductive filler TA@CNTs@ZnO, for later use; S2: Preparation of rubber adhesive Mix 10-60 parts of terpene resin and 40-90 parts of rubber on a two-roll mill, then add stearic acid, the heterogeneous thermally conductive filler prepared in S1, 0.01-0.05 parts of peroxide crosslinking agent, and 0.01-0.03 parts of co-crosslinking agent in sequence, and mix evenly. Place the mixed rubber in a mold, cover the top and bottom with polytetrafluoroethylene mold, and hot press at 150-180℃ and 5-15 MPa for 10-30 min to obtain a thermally conductive rubber-based adhesive.

4. The preparation method according to claim 3, characterized in that, In step S1, the molar ratio of FeCl3·6H2O to tannic acid is 1:5 to 1:10.

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