CN116874826B

CN116874826B - Heat-conducting silicone rubber composite material with directional arrangement of fillers and preparation method thereof

Info

Publication number: CN116874826B
Application number: CN202310916014.7A
Authority: CN
Inventors: 蒋天刚; 李培仙; 周乐添
Original assignee: Changzhou Hongju Electronic Technology Co ltd
Current assignee: Changzhou Hongju Electronic Technology Co ltd
Priority date: 2023-07-25
Filing date: 2023-07-25
Publication date: 2023-12-22
Anticipated expiration: 2043-07-25
Also published as: CN116874826A

Abstract

The invention belongs to the technical field of heat conduction materials, and particularly relates to a heat conduction silicon rubber composite material with directional arrangement of fillers and a preparation method thereof. Uniformly mixing methyl vinyl solid silicon rubber, a vulcanizing agent and other additives, pressing into a silicon rubber film with a certain thickness through a calender, then placing the silicon rubber film into a polytetrafluoroethylene mold, preparing a filler-silicon rubber slurry from a heat-conducting filler, hydroxyl silicone oil and a solvent, pouring the slurry into the polytetrafluoroethylene mold filled with a silicon rubber film, heating to remove the solvent to obtain a double-layer film of a lower silicon rubber layer of an upper filler layer, performing plasma treatment and cutting on the double-layer film, inwards curling the silicon rubber film from the edge to form a core-shell structure with the inside of the heat-conducting filler and the outside of the silicon rubber, cutting the silicon rubber film into a core-shell structure with the same length and vertically arranging the silicon rubber film, and finally performing hot press vulcanization to obtain the heat-conducting silicon rubber composite material with the filler arranged in a directional manner. The silicon rubber composite material has high thermal conductivity and is suitable for most heat conduction filler systems.

Description

Heat-conducting silicone rubber composite material with directional arrangement of fillers and preparation method thereof

Technical Field

The invention belongs to the technical field of heat conduction materials, and particularly relates to a heat conduction silicon rubber composite material with directional arrangement of fillers and a preparation method thereof.

Background

With the development of electronic technology, the miniaturization, high integration, high heat flux density and other features of electronic devices have put higher demands on the thermal management of integrated circuit electronic devices. The heat-conducting silicon rubber composite material is one of common thermal interface materials, has good high and low temperature resistance, insulativity and weather resistance,and has the advantages of easy processing, easy adjustment of product thickness and hardness, etc. Since the heat conductivity of the silicone rubber is very low (0.16-0.2 W.m ^-1 ·K ^-1 ) High heat conductivity filler is required to be added to improve the heat conductivity of the silicone rubber composite material. Common thermally conductive fillers include: metals (gold, silver, copper, aluminum, etc.), carbon-based materials (expanded graphite, graphene, carbon nanotubes, etc.), and ceramic-based fillers (alumina, boron nitride, silicon carbide, etc.). But the heat conduction coefficient of the heat conduction silicon rubber prepared by the common blending method is lower, and the application requirement is difficult to meet.

At present, a method for constructing a heat conduction path in a matrix is widely focused, and a directional high-speed heat conduction path is formed by locally and directionally arranging fillers, so that the heat conduction performance of the composite material is improved. However, currently, the commonly studied methods, such as an ice template method, a layer-by-layer assembly method, a suction filtration assembly method and the like, have complicated steps and are difficult to industrialize. Moreover, these methods have certain requirements for the choice of filler and are difficult to apply to different filler systems. In addition, it is difficult to construct an oriented arrangement of the filler in the solid rubber. Therefore, it is highly desirable to invent a simple and easy-to-use method for forming a heat conduction path in solid silicone rubber.

Disclosure of Invention

The invention aims to overcome the defects in the background art and provides a heat-conducting silicone rubber composite material with directional arrangement of fillers and a preparation method thereof.

The aim of the invention can be achieved by the following technical scheme:

(1) Uniformly mixing methyl vinyl solid silicon rubber, a vulcanizing agent and other assistants according to a certain proportion, pressing the mixture into a silicon film with the thickness of 0.5mm by a calender, and then placing the silicon film into a polytetrafluoroethylene die;

wherein the vulcanizing agent is one or more of 2, 5-dimethyl-2, 5-bis (tert-butyl peroxide) hexane, 2, 4-dichloro benzoyl peroxide and dicumyl peroxide.

The other auxiliary agent is one or more of hydroxyl silicone oil, hydrogen-containing silicone oil, gamma-methacryloxypropyl trimethoxy silane KH570 and gamma-aminopropyl triethoxy silane KH 550.

The weight ratio of the methyl vinyl solid silicon rubber to the vulcanizing agent to other auxiliary agents is 70-95:1-5:3-29.

The weight ratio of the methyl vinyl solid silicon rubber, the vulcanizing agent and other auxiliary agents is preferably 80-90:2-4:6-18.

(2) Preparing a heat conducting filler, hydroxyl silicone oil and a solvent into filler-silica gel slurry, pouring the filler-silica gel slurry into a silica gel film surface arranged in a polytetrafluoroethylene die, flattening, and heating to remove the solvent to obtain a double-layer film of a lower silica gel layer of an upper filler layer;

wherein, the weight ratio of the heat conduction filler to the hydroxyl silicone oil to the solvent is 50-70:5-10:20-45. The proportion is controlled to enable the filler to be deposited more uniformly on the surface of the silica gel layer, and the hydroxy silicone oil can carry out wet modification on the heat-conducting filler to prevent the filler from falling off in the curling process.

The weight ratio of the heat conducting filler, the hydroxyl silicone oil and the solvent is preferably 50-60:5-10:30-45.

The heat conducting filler is one or more of aluminum oxide, boron nitride, aluminum nitride, silicon carbide and carbon fiber.

The heat conductive filler is preferably boron nitride, aluminum nitride, silicon carbide.

The solvent is one of tetrahydrofuran, n-hexane and cyclohexane. The choice of solvent depends on the dispersibility of the filler in the solvent.

The temperature for heating to remove the solvent is 60-80 ℃.

The weight ratio of the filler layer to the silica gel layer in the double-layer film is 1:5-10.

The weight ratio of the filler layer to the silica gel layer in the double-layer film is preferably 1:5-8.

(3) And after the double-layer film is subjected to plasma treatment and cut in order, the double-layer silica gel mold is curled inwards from the edge to be connected end to form a core-shell structure with the heat conducting filler inside and the silicone rubber outside, the core-shell structure is cut into cylinders with the same length, the cylinders are transversely stacked and then rotated for 90 degrees to be vertically arranged, and finally, the silicone rubber composite material with the directional arrangement of the filler is obtained through hot pressing and vulcanization.

Wherein the plasma treatment time is 1-3s, and the treatment power is 30-80W. After plasma treatment, active groups and free radicals are generated in the filler and the silicone rubber, and the interface binding force between the filler and the silicone rubber can be further enhanced in the curing process of the silicone rubber. In addition, the plasma treatment can pre-crosslink the rubber to increase the hardness of the rubber layer to maintain its shape during stacking and rotation.

Cutting the core-shell structure silicon rubber into a silicon rubber strip with the length of 5mm-50mm, wherein the curing pressure is 10-20MPa, the curing temperature is 100-150 ℃, and the curing time is 15-40min. The thickness of the heat conduction product can be adjusted by adjusting the length of the cut core-shell structure silicone rubber strip, the silicone rubber can deform under the curing pressure so as to fill the filler gap, the whole material is ensured to be free of defects, and the silicone rubber can be ensured to be completely cured within the curing temperature and curing time range.

Compared with the prior art, the invention has the following advantages:

(1) The preparation method of the invention can lead the filler to form a structure which is vertically arranged in the solid rubber, and greatly improves the directional heat conducting performance of the composite material.

(2) The surface of the filler and the surface of the silicon rubber after the plasma modification generate active groups and free radicals, so that the filler can interact with the silicon rubber and the auxiliary agent in the curing process of the silicon rubber, thereby improving the bonding force of the interface of the filler and the silicon rubber.

(3) The preparation method is suitable for most of fillers, has universality, and can be used for developing heat-conducting silicone rubber products of different systems.

Description of the drawings:

in order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention.

Fig. 1 is a schematic diagram of a core-shell structure of a thermally conductive filler-silicone rubber.

Fig. 2 is a schematic structural view of a silicone rubber composite with aligned filler.

FIG. 3 is an SEM image of an alumina/silicone rubber composite with the filler oriented in example 1.

Detailed Description

Example 1

The preparation method of the silicon rubber composite material with the directional arrangement of the aluminum oxide comprises the following steps:

(1) 95 parts of methyl vinyl solid silicone rubber, 2 parts of 2, 5-dimethyl-2, 5-bis (tert-butyl peroxide) hexane vulcanizing agent and 3 parts of hydroxyl silicone oil are uniformly mixed by a mixer, and the mixture is subjected to a roll ratio of 1 at room temperature by a calender: 1, pressing to form a silica gel film with the thickness of 0.5mm, and then placing the silica gel film in a polytetrafluoroethylene die.

(2) Preparing 70 parts of alumina, 10 parts of hydroxyl silicone oil and 20 parts of tetrahydrofuran into alumina-silica gel slurry, pouring the slurry into a polytetrafluoroethylene mold, flattening the surface of a silica gel film, heating to 70 ℃ to remove a solvent, and obtaining a double-layer film of an upper alumina layer and a lower silica gel layer, wherein the weight ratio of the alumina layer to the silica gel layer is 1:10.

(3) And (3) carrying out plasma treatment on the double-layer film at 80W power for 3s and cutting the double-layer film in order, then inwards curling the double-layer silica gel film from the edge to end to form a core-shell structure with aluminum oxide inside and silicon rubber outside, cutting the double-layer film into small cylinders with the diameter of 20mm, transversely stacking the small cylinders, changing the rotation direction of the small cylinders into vertical arrangement by 90 degrees, and finally carrying out hot press vulcanization for 10min at the temperature of 120 ℃ and the pressure of 10MPa to obtain the aluminum oxide/silicon rubber composite material with the directional arrangement of the filler.

Example 2

A preparation method of a silicon rubber composite material with oriented arrangement of boron nitride comprises the following steps:

(1) 75 parts of methyl vinyl solid silicone rubber, 3 parts of 2, 4-dichloro benzoyl peroxide vulcanizing agent, 10 parts of hydroxyl silicone oil, 5 parts of KH570 and 7 parts of hydrogen-containing silicone oil are uniformly mixed by a mixing mill, and the mixture is subjected to a roll ratio of 1 at room temperature by a calender: 1, pressing to form a silica gel film with the thickness of 0.5mm, and then placing the silica gel film in a polytetrafluoroethylene die.

(2) Preparing 50 parts of boron nitride, 5 parts of hydroxyl silicone oil and 45 parts of normal hexane into boron nitride-silica gel slurry, then pouring the slurry into a polytetrafluoroethylene mold, flattening the surface of a silica gel film, heating to 70 ℃ to remove a solvent, and obtaining a double-layer film of an upper boron nitride layer and a lower silica gel layer, wherein the weight ratio of the boron nitride layer to the silica gel layer is 1:8.

(3) And (3) carrying out plasma treatment on the double-layer film at 50W power for 3s and trimming, then inwards curling the double-layer silica gel film from the edge to form a core-shell structure with the inside of boron nitride and the outside of silicon rubber, trimming the double-layer film into a small cylinder with the thickness of 50mm, transversely stacking the small cylinder, rotating the small cylinder for 90 degrees to be vertically arranged, and finally carrying out hot press vulcanization for 40min under the conditions of the temperature of 150 ℃ and the pressure of 20MPa to obtain the boron nitride/silicon rubber composite material with the directionally arranged fillers.

Example 3

The preparation method of the silicon rubber composite material with the aluminum nitride directionally arranged comprises the following steps:

(1) 85 parts of methyl vinyl solid silicone rubber, 3 parts of dicumyl peroxide vulcanizing agent, 4 parts of dimethyl silicone oil, 4 parts of hydroxyl silicone oil and 4 parts of KH550 are uniformly mixed by a mixing mill, and the mixture is subjected to a roll ratio of 1 at room temperature by a calender: 1, pressing to form a silica gel film with the thickness of 0.5mm, and then placing the silica gel film in a polytetrafluoroethylene die.

(2) Preparing aluminum nitride-silica gel slurry from 60 parts of aluminum nitride, 5 parts of hydroxyl silicone oil and 35 parts of cyclohexane, pouring the slurry into a polytetrafluoroethylene mold, flattening the surface of a silica gel film, heating to 60 ℃ to remove a solvent to obtain a double-layer film of an upper aluminum nitride layer and a lower silica gel layer, wherein the weight ratio of the aluminum nitride layer to the silica gel layer is 1:5.

(3) And (3) carrying out plasma treatment on the double-layer film at 80W power for 1s and trimming, then inwards curling the double-layer silica gel film from the edge to form a core-shell structure with aluminum nitride inside and silicon rubber outside, trimming the double-layer film into small cylinders with the diameter of 10mm, vertically arranging the small cylinders, and finally carrying out hot press vulcanization for 30min at the temperature of 100 ℃ and the pressure of 20MPa to obtain the aluminum nitride/silicon rubber composite material with the directional arrangement of the filler.

Example 4

A preparation method of a silicon rubber composite material with silicon carbide directionally arranged comprises the following steps:

(1) 80 parts of methyl vinyl solid silicone rubber, 4 parts of 2, 5-dimethyl-2, 5-bis (tert-butyl peroxide) hexane vulcanizing agent, 8 parts of hydroxyl silicone oil and 8 parts of KH550 are uniformly mixed by a mixing mill, and the mixture is subjected to a roll ratio of 1 at room temperature by a calender: 1, pressing to form a silica gel film with the thickness of 0.5mm, and then placing the silica gel film in a polytetrafluoroethylene die.

(2) Preparing silicon carbide-silica gel slurry from 60 parts of silicon carbide, 10 parts of hydroxyl silicone oil and 30 parts of tetrahydrofuran, pouring the slurry into a polytetrafluoroethylene mold, flattening the surface of a silica gel film, heating to 60 ℃ to remove a solvent to obtain a double-layer film of an upper silicon carbide layer and a lower silicon gel layer, wherein the weight ratio of the silicon carbide layer to the silicon rubber layer is 1:7.

(3) And (3) carrying out plasma treatment on the double-layer film at 70W power for 2s and trimming, then inwards curling the double-layer silica gel film from the edge to form a core-shell structure with silicon carbide inside and silicon rubber outside, trimming the double-layer film into small cylinders with the diameter of 10mm, vertically arranging the small cylinders, and finally carrying out hot pressing vulcanization for 30min at the temperature of 100 ℃ and the pressure of 20MPa to obtain the silicon carbide/silicon rubber composite material with the directional arrangement of the filler.

Example 5

A preparation method of a silicon rubber composite material with carbon fibers arranged in an oriented manner comprises the following steps:

(1) 90 parts of methyl vinyl solid silicone rubber, 2 parts of 2, 5-dimethyl-2, 5-bis (tert-butyl peroxide) hexane vulcanizing agent, 4 parts of hydroxyl silicone oil and 4 parts of KH570 are uniformly mixed by a mixing mill, and the mixture is subjected to a roll ratio of 1 at room temperature by a calender: 1, pressing to form a silica gel film with the thickness of 0.5mm, and then placing the silica gel film in a polytetrafluoroethylene die.

(2) Preparing carbon fiber-silica gel slurry from 50 parts of carbon fiber, 10 parts of hydroxyl silicone oil and 40 parts of tetrahydrofuran, pouring the slurry into a polytetrafluoroethylene mold, flattening the surface of a silica gel film, heating to 60 ℃ to remove a solvent to obtain a double-layer film of an upper carbon fiber layer and a lower silica gel layer, wherein the weight ratio of the carbon fiber layer to the silica gel layer is 1:9.

(3) And (3) carrying out plasma treatment on the double-layer film at 80W power for 2s and trimming, then inwards curling the double-layer silica gel film from the edge to form a core-shell structure with carbon fibers inside and silicon rubber outside, trimming the double-layer film into small cylinders with the diameter of 30mm, vertically arranging the small cylinders, and finally carrying out hot pressing vulcanization for 20min at the temperature of 120 ℃ and the pressure of 20MPa to obtain the carbon fiber/silicon rubber composite material with the directional arrangement of the fillers.

Example 6

In comparison with example 2, the thermally conductive filler used in this example was silicon carbide, and the other steps were the same as in example 2.

Example 7

In comparison with example 2, the thermally conductive filler used in this example was aluminum nitride, and the other steps were the same as in example 2.

Example 8

In comparison with example 2, the methyl vinyl solid silicone rubber, 2, 4-dichloroperoxide benzoyl vulcanizing agent, hydroxy silicone oil and KH570 used in this example were 90 parts, 4 parts, 3 parts and 3 parts, respectively. Otherwise, the same as in example 2 is carried out.

Example 9

Compared with example 2, the boron nitride, the hydroxyl silicone oil and the n-hexane used in this example were 60 parts, 10 parts and 30 parts, respectively. Otherwise, the same as in example 2 is carried out.

Example 10

Compared with example 2, the weight ratio of the boron nitride layer and the silicone rubber layer used in this example was 1:5. otherwise, the same as in example 2 is carried out.

Example 11

Compared with example 2, the weight ratio of the boron nitride layer and the silicone rubber layer used in this example was 1:10. otherwise, the same as in example 2 is carried out.

Example 12

In comparison with example 2, the plasma treatment power used in this example was 50W and the treatment time was 1s. Otherwise, the same as in example 2 is carried out.

Example 13

In comparison with example 1, the thermally conductive filler used in this example was alumina and silicon carbide 1:1, and mixing. Otherwise, the same as in example 1 was conducted.

Example 14

Compared with example 1, the heat conductive filler used in this example was alumina and carbon fiber 1:1, and mixing. Otherwise, the same as in example 1 was conducted.

Comparative example 1

In contrast to example 1, no hydroxy silicone oil was added to the comparative silicone film.

Comparative example 2

In contrast to example 1, no hydroxy silicone oil was added to the comparative alumina-silica gel slurry.

Comparative example 3

In contrast to example 1, the comparative bilayer film was not plasma treated.

Comparative example 4

(2) 70 parts of alumina, 10 parts of hydroxyl silicone oil and 20 parts of tetrahydrofuran are prepared into alumina-silica gel slurry, then the slurry is poured on the surface of a silica gel film in a polytetrafluoroethylene mold, and the slurry is heated to 70 ℃ to remove a solvent, so that a double-layer film of an upper alumina layer and a lower silica gel layer is obtained, wherein the weight ratio of the alumina layer to the silica gel layer is 1:10.

(3) And (3) carrying out plasma treatment on the double-layer film at 80W power for 3s, curling the silica gel film from the edge inwards to be connected end to form a core-shell structure with aluminum oxide inside and silicon rubber outside, then transversely stacking, and finally carrying out hot press vulcanization for 10min at the temperature of 120 ℃ and the pressure of 10MPa to obtain the aluminum oxide/silicon rubber composite material with the directional arrangement of the fillers.

Evaluation:

the heat conductive properties and mechanical properties of the heat conductive silicone rubbers with the filler orientation arrangement prepared in the above examples 1 to 11 of the present invention were tested as follows, and the results are shown in Table 1.

Thermal conductivity testing standard test methods for heat transfer characteristics of thermally conductive materials according to ASTM D5470-2017.

Mechanical property testing was according to the standard method of GB/T528-1998.

TABLE 1 Heat conducting Properties and mechanical Properties of Heat conducting Silicone rubber with oriented filler arrangement

As can be seen from the table, the oriented heat-conducting silicone rubber prepared by the invention has excellent heat-conducting property in orientation. As can be seen from comparison of examples 1, 2, 6 and 7, the effect of improving the heat conduction property is boron nitride > aluminum nitride > silicon carbide > aluminum oxide. The addition of the auxiliary agent can be used for interaction with the filler in comparison with examples 1, 2 and 8, comparative examples 1 and 2, and can increase the heat conduction performance and mechanical performance of the heat conduction silicone rubber product, the addition of the filler can be used for increasing the heat conduction performance of the silicone rubber product in comparison with examples 2 and 9, the weight ratio of the filler layer to the silica gel layer can be increased in comparison with examples 2 and 10 and examples 11, and the heat conduction performance and mechanical performance of the silicone rubber product can be improved in comparison with examples 1, 2 and 12 and comparative example 3, and the heat conduction performance and mechanical performance of the silicone rubber product can be improved in comparison with examples 1, 13 and 14. As can be seen from a comparison of example 1 and comparative example 4, the vertically aligned structure of the present invention can effectively improve the heat conductive properties of the material.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims

1. The preparation method of the heat-conducting silicone rubber composite material with the directional arrangement of the fillers is characterized by comprising the following steps:

(1) Uniformly mixing methyl vinyl solid silicon rubber, a vulcanizing agent and other assistants in proportion, pressing the mixture into a silicon film with the thickness of 0.5mm by a calender, and then placing the silicon film into a polytetrafluoroethylene die;

the other auxiliary agents are one or more of hydroxyl silicone oil, hydrogen silicone oil, gamma-methacryloxypropyl trimethoxy silane KH570 and gamma-aminopropyl triethoxy silane KH 550; the weight ratio of the methyl vinyl solid silicon rubber to the vulcanizing agent to other auxiliary agents is 70-95:1-5:3-29;

(2) Preparing a heat-conducting filler, hydroxyl silicone oil and a solvent into filler-silica gel slurry, pouring the slurry into the silica gel film surface which is placed in a polytetrafluoroethylene die in the step (1), flattening the silica gel film surface, and heating to remove the solvent to obtain a double-layer film of a lower silica gel layer of an upper filler layer;

the heat conducting filler is one or more of aluminum oxide, boron nitride, aluminum nitride, silicon carbide and carbon fiber; the solvent is one of tetrahydrofuran, n-hexane and cyclohexane;

the weight ratio of the heat conducting filler to the hydroxyl silicone oil to the solvent is 50-70:5-10:20-45;

the weight ratio of the filler layer to the silica gel layer in the double-layer film is 1:5-10;

(3) After the double-layer film is subjected to plasma treatment and cutting, the double-layer silica gel film is curled inwards from the edge to end to form a core-shell structure with the heat conducting filler inside and the silicone rubber outside, then the core-shell structure is cut into cylinders with the same length, the cylinders are transversely stacked and then rotated for 90 degrees to be vertically arranged, and finally the silicone rubber composite material with the directional arrangement of the filler is obtained through hot pressing and vulcanization.

2. The method for preparing the heat-conducting silicone rubber composite material with the directional arrangement of the fillers according to claim 1, wherein the vulcanizing agent in the step (1) is one or more of 2, 5-dimethyl-2, 5-bis (tert-butyl peroxide) hexane, 2, 4-dichloro benzoyl peroxide and dicumyl peroxide.

3. The method for preparing a heat conductive silicone rubber composite with aligned filler according to claim 1, wherein the temperature for heating to remove the solvent in the step (2) is 60-80 ℃.

4. The method for preparing a heat conductive silicone rubber composite material with directional arrangement of fillers according to claim 1, wherein the plasma treatment time in the step (3) is 1-3s, and the treatment power is 30-80W.

5. The method for preparing the heat-conducting silicone rubber composite material with the directional arrangement of the fillers according to claim 1, wherein in the step (3), the silicone rubber with the core-shell structure is cut into cylinders with the length of 5mm-50mm, the hot press vulcanization pressure is 10-20MPa, the hot press vulcanization temperature is 100-150 ℃, and the hot press vulcanization time is 15-40min.

6. A thermally conductive silicone rubber composite with an oriented arrangement of fillers prepared according to the method of any one of claims 1-5.