CN115725182B - A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler and its preparation method and application - Google Patents

Abstract

The invention discloses a silicone rubber composite material containing phase change nanocapsule/boron nitride hybrid filler, its preparation method and application. The silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler is made of the following raw materials (calculated in mass fraction): phase change nanocapsules/boron nitride hybrid filler 10% to 60%, silicone rubber Prepolymer 20% ~ 45% and curing agent 20% ~ 45%, the sum of the above raw materials is 100%. The phase change nanocapsule/boron nitride hybrid filler formed by electrostatic self-assembly helps reduce the interface thermal resistance in silicone rubber and improves thermal conductivity. Used as a thermal interface material, this material is expected to fill the air gap, alleviate the thermal shock of the chip when facing high heat flux density, and help chips, electronic devices, etc. better dissipate heat.

Description

A silicone rubber composite material containing phase change nanocapsule/boron nitride hybrid filler and Preparation methods and applications

Technical field

The invention belongs to the technical field of composite material heat storage, and specifically relates to a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, its preparation method and application.

Background technique

Introducing phase change materials into polymer matrices can develop flexible composite materials with latent heat storage capabilities, which have important applications in lithium-ion battery thermal management, chip heat dissipation and other fields. Compared with solid-solid phase change materials, solid-liquid phase change materials have higher latent heat and rich types, so they are often used to prepare flexible phase change composites. The leakage problem of liquid PCM is an inherent defect of solid-liquid phase change materials and needs to be overcome in practical applications. One widely adopted solution is to directly mix organic solid-liquid phase change materials (such as paraffin) with polymers and then fuse them to obtain shape-stable composites. In morphologically stable composites, organic phase change materials are present in interpenetrating polymer networks, thus preventing leakage of liquid phase change materials. However, these composites still have the risk of liquid leakage after undergoing multiple heating-cooling cycles during long-term use. Research has found that encapsulating solid-liquid phase change materials into shells to synthesize phase change capsules is an effective method to separate the external environment and prevent its liquid from leaking. Clearly, combining phase change capsules with a polymer matrix is a more preferable approach to develop flexible phase change composites with good thermal reliability. Usually, the thermal conductivity of introducing phase change capsules into the polymer matrix is relatively low, which is not enough to quickly export heat under high-power heating conditions. The introduction of high thermal conductivity materials can increase the thermal conductivity of composite materials, but the introduction of high thermal conductivity fillers (such as boron nitride) usually has poor compatibility with the matrix. When directly blended with the phase change capsule and introduced into the polymer matrix, there is no interaction, which can easily lead to a decrease in the interfacial thermal resistance of the filler-filler and filler-matrix of the composite material. Larger, so the thermal conductivity cannot be improved ideally, making it difficult to achieve subsequent demoulding and final application. Surface modification of highly thermally conductive fillers is a commonly used process to enhance dispersion, but this method only considers highly thermally conductive fillers and does not form a connection with the phase change capsule, so the interfacial thermal resistance between fillers and fillers is still relatively low. Large, and the immaturity of the existing surface modification process leads to low filler modification efficiency and low output.

Patent CN102241963A "High Thermal Conductivity Shaped Phase Change Energy Storage Material and Manufacturing Method" discloses a composite material composed of microcapsules of hydrated salt@polymer shell and thermally conductive metal powder as fillers, but the mixing method of the fillers is direct Randomly dispersed, which makes it easy for the same fillers to agglomerate with each other due to high surface energy, making it difficult to build a good interface and affecting the thermal conductivity and mechanical properties of the material. Patent CN114774086A "A Thermal Conductivity Enhanced Phase Change Nanocapsule Composite Material and Preparation Method and Application" mentions that the surface of the inorganic shell nanocapsule has abundant hydroxyl groups, which can form hydrogen with the curing agent of polydimethylsiloxane. bond, which enhances the compatibility with the matrix and reduces the hardness of the material. However, when mixed with the high thermal conductive filler, it is still added in a direct random dispersion manner. This method makes the interface between the high thermal conductive filler, the capsule and the matrix The thermal resistance is still large and it is difficult to further improve the thermal conductivity.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler and its preparation method and application. The phase change nanocapsules and high thermal conductivity materials are electrostatically The self-assembly method forms hybrid fillers and then introduces them into the polymer matrix, which solves the problem in the existing technology that the phase-change nanocapsules are directly mixed with high thermal conductivity materials and the polymer is easily agglomerated, especially when the amount of filler added is high. It often brings greater interface thermal resistance, deteriorating the thermal conductivity and mechanical properties of the material. After forming the phase change nanocapsule/boron nitride hybrid filler and then adding it to the matrix, the interface thermal resistance between the nanocapsule and boron nitride can be effectively reduced, and the boron nitride and the matrix can be bonded more effectively through the capsule. For compactness, the interfacial thermal resistance between the filler and the matrix is reduced.

The present invention prepares phase change nanocapsules/boron nitride hybrid fillers through an electrostatic self-assembly process, and then adds the hybrid fillers as a whole into the polymer matrix to enhance the dispersion of the phase change nanocapsules and high thermal conductivity fillers in the matrix. The interfacial thermal resistance between the system filler-filler and filler-matrix was reduced, and a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler was finally prepared and used as a phase change thermal interface material.

The object of the present invention is achieved through the following technical solutions.

A method for preparing a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, including the following steps:

(1) Use interfacial hydrolysis-condensation polymerization method to prepare paraffin@silica phase change nanocapsules;

(2) Use acid solution to adjust the pH to acidic under 1000mL solvent dispersion. Stir sodium polystyrene sulfonate (PSS) and boron nitride for 6 to 12 hours, let it stand for 12 to 24 hours and then filter to make the negatively charged polystyrene sulfonic acid Sodium is deposited on the boron nitride surface;

(3) Add the paraffin@silica phase change nanocapsules obtained in steps (1) and (2) and the boron nitride deposited by negatively charged sodium polystyrene sulfonate in different mass proportions in the container, add 100 mL of solvent to disperse, and acid The pH of the liquid is adjusted to make the silica shell positively charged, stirred for 6-8 hours to perform the electrostatic self-assembly process, vacuum filtered, and dried to obtain the phase change nanocapsule/boron nitride hybrid filler;

(4) Add the hybrid filler, silicone rubber matrix prepolymer and curing agent obtained in step (3) to a planetary mixer for stirring. The stirring program is set to 500 to 1000 rpm and the time is 3 to 6 minutes;

(5) Coat the glue obtained in step (4) into a 20×20×1mm mold, place it in a vacuum degassing barrel, and degas at 25°C to 40°C and 80kPa to 100kPa for 20 to 30 minutes; take it out Then, it is left to stand at 25° C. for 48 hours to solidify and form. After demoulding, the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler is obtained.

Preferably, the interfacial hydrolysis-polycondensation method in step (1) is specifically: anhydrous ethanol, deionized water, and cetyldimethylammonium bromide (CTAB) constitute the aqueous phase, and the core material and shell material precursors To form an oil phase, the water phase and the oil phase are first fully dissolved at 60°C, and then mixed together to form a stable O/W emulsion through the emulsification process; an ammonia initiator is added, and the shell material precursor is hydrolyzed and polycondensed at the interface through ammonia catalysis The reaction forms shell oligomers, which are negatively charged. They are immediately adsorbed on the surface of positively charged micelles through electrostatic interactions. As the interfacial polycondensation reaction proceeds, the shell oligomers continue to migrate from the inside of the oil droplet to the interface. , and finally gradually condense to form an inorganic shell on the surface of the core material droplet.

Preferably, the particle size of the paraffin@silica phase change nanocapsules described in step (1) is 800-1000nm, the phase-change temperature is 42°C-48°C, and the latent heat of phase-change is 120-180J/g.

Preferably, the solvent described in steps (2) and (3) is one or more of deionized water and ethanol.

Preferably, the acid solution in steps (2) and (3) is one or more of 1 mol·L ^-1 dilute hydrochloric acid and dilute sulfuric acid.

Preferably, the mass ratio used in step (3) is paraffin @ silica phase change nanocapsules: boron nitride deposited with negatively charged sodium polystyrene sulfonate = 2:1 or 1:1 or 1:2.

Preferably, the pH in step (3) is 1-5.

Preferably, the curing agent in step (4) is one or a mixture of hydrogen-containing silicone oil, hydrogen-containing silicone oil, and methyl hydrogen-containing silicone oil.

A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler obtained by the above preparation method, in terms of mass fraction, the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler It includes phase change nanocapsule/boron nitride hybrid filler 10% to 60%, silicone rubber prepolymer 20% to 45% and curing agent 20% to 45%. The sum of the above raw materials is 100%.

Preferably, the heat storage performance of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler is a phase change enthalpy value of 12-54J/g, and the thermal conductivity performance is a thermal conductivity of 0.44-1.28W/ (m·K), the hardness at normal temperature (25℃) is 25~50HA.

The present invention also provides the application of the above-mentioned silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler as a thermal interface material. By placing the silicone rubber composite containing phase change nanocapsules/boron nitride hybrid filler as a thermal pad between the chip and the radiator heat sink, the soft composite material will fill the gap between the chip and the radiator heat sink. The air gap can better dissipate the heat generated by the chip in a timely manner, and play a certain thermal buffering role, so that the chip shows good heat dissipation performance under different working conditions.

The technical solution of the present invention adopts the following principles:

(1) Principle of isoelectric point on the surface of silica: Taking advantage of the unique isoelectric point properties of silica, there will be an isoelectric point around pH=2. When the pH is less than this isoelectric point, the silica will On the other hand, when the pH is greater than the isoelectric point, the silica will be negatively charged. Therefore, the larger size of the phase change nanocapsule silica shell surface can be controlled by adjusting the pH to be lower than the isoelectric point. Positive potential.

(2) Electrostatic self-assembly principle: The present invention uses electrostatic adsorption force to make two substances with positive and negative Zeta potentials (i.e., positively charged paraffin@silica phase change nanocapsules and negatively charged polystyrene sulfonic acid Sodium-deposited boron nitride) is tightly combined. In this process, the pH, salt ions, solvents, and Zeta potential can be changed to change the adsorption force of the filler. The greater the absolute value of the Zeta potential, the stronger the binding force and the more stable the system. .

Compared with the existing technology, the present invention has the following advantages and beneficial effects:

(1) The present invention directly uses the method of controlling the isoelectric point of silica to make the silica shell of the phase change nanocapsule positively charged, avoiding the repeated deposition of a positively charged coating on the surface of the silica shell to make it positively charged. The complex process of electricity enables effective electrostatic self-assembly with negatively charged deposited sodium polystyrene sulfonate-coated boron nitride.

(2) The present invention uses an electrostatic self-assembly method with mild reaction conditions to construct a phase change nanocapsule/boron nitride hybrid filler. The hybrid filler has a new lotus seed-lotus pod structure, with slices and balls connected. This structure is beneficial to The interface thermal resistance between nanocapsules and boron nitride is reduced, and the material prepared by this method is more uniform and does not cause the loss of the thermal conductivity of the filler itself, which is beneficial to improving the thermal conductivity.

(3) The silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler prepared by the present invention has good interface compatibility. On the one hand, electrostatic self-assembly reduces the interfacial thermal resistance between fillers; on the other hand, On the other hand, the surface of silica nanocapsules is rich in hydroxyl groups, which can form hydrogen bonds with the curing agent, and the thermal resistance at the interface with the matrix is low. On the contrary, the thermal resistance at the interface between boron nitride and the matrix is very large, which combines the self-assembly of the nanocapsules. On boron nitride, it will be beneficial to reduce the interfacial thermal resistance between the filler and the matrix. Due to the good filler-filler and filler-matrix interface states, the gasket can be completely demoulded at a higher filling amount, further improving the thermal conductivity of the composite material.

Description of drawings

Figure 1 is a flow chart for the preparation of silicone rubber composite materials containing phase change nanocapsules/boron nitride hybrid fillers of the present invention.

Figure 2 is a comparative view of the micromorphology of self-assembled phase change nanocapsules/boron nitride hybrid fillers and directly mixed phase change nanocapsules/boron nitride fillers in Example 1 of the present invention.

Figure 3 is a diagram showing an application example of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler as a thermal interface material according to Embodiment 1 of the present invention.

Figure 4 shows the silicone rubber composite material containing phase change nanocapsule/boron nitride hybrid filler as the thermal interface material and the directly mixed phase change nanocapsule/boron nitride/silicone rubber composite material as the thermal interface in Embodiment 1 of the present invention. Comparison chart of chip temperature change curves of materials.

Specific example method

The embodiments of the present invention will be described in further detail below with reference to the examples and drawings, but the embodiments of the present invention are not limited thereto.

The preparation flow chart of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler of the present invention is shown in Figure 1. First, the paraffin@silica phase change nanocapsules were prepared by interfacial hydrolysis-condensation polymerization method. Then use acid solution to adjust the pH under solvent dispersion, add polystyrene sulfonate (PSS) and boron nitride, stir, let stand and then filter, so that the negatively charged PSS is deposited on the surface of boron nitride. Add the obtained paraffin@silica phase change nanocapsules and negatively charged PSS-deposited boron nitride in different proportions in the container, add solvent to disperse, adjust pH with acid solution to make the silica shell positively charged, stir, and vacuum filter. After drying, the phase change nanocapsule/boron nitride hybrid filler is obtained. Put the phase change nanocapsule/boron nitride hybrid filler, silicone rubber prepolymer and curing agent into a planetary mixer and stir. The obtained rubber material is coated in the mold, placed in a vacuum degassing barrel, and degassed. Finally, it is taken out, left to solidify and molded, and the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler is obtained after demoulding.

Example 1

A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, made of the following raw materials in terms of mass fraction: phase change nanocapsules/boron nitride hybrid filler 60%, silicone rubber prepolymer 20% and hydrogenated silicone oil 20%.

The preparation method of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler includes the following steps:

(1) Use the interfacial hydrolysis-polycondensation method to prepare phase change nanocapsules with paraffin as the core material and silica as the shell material: paraffin (15.0g), ethyl orthosilicate TEOS (7.5g) in a 250mL three-neck flask. Stir and mix at 60°C to form a transparent solution. Then, cetyltrimethylammonium bromide CTAB (0.82g), deionized water (35.5mL) and absolute ethanol (71.25mL) were added to a 250mL beaker at the same time, and kept warm to 60°C. Add the aqueous phase composed of absolute ethanol, deionized water, and CTAB to the oil phase composed of paraffin and TEOS at 60°C, and mechanically stir at 350 rpm for 4 hours to form a stable O/W emulsion. Add 1.5 mL of 25 wt% ammonia water and keep stirring at 60°C for 16 h to catalyze the interfacial hydrolysis-condensation polymerization reaction of TEOS. Finally, after filtering, washing with deionized water, washing with petroleum ether, and drying, about 8 g of white powder, namely paraffin@silica phase change nanocapsules, was obtained.

(2) Use 1 mol·L ^-1 dilute hydrochloric acid to adjust the pH to 3 while dispersed in 1000 mL deionized water. Stir 3 g sodium polystyrene sulfonate (PSS) and 10 g boron nitride for 12 hours, let it stand for 24 hours and then filter to make it negatively charged. PSS is deposited on the boron nitride surface.

(3) Add 10g of the paraffin@silica phase change nanocapsules obtained in steps (1) and (2) (average particle size 800nm, phase change temperature 42°C, latent heat value 160J/ g), add 100 mL of deionized water to disperse the boron nitride deposited by negative PSS, adjust the pH to 2 with hydrochloric acid to make the silica shell positively charged, stir for 6 hours, vacuum filter, and dry to obtain the phase change nanocapsules/nitrogen Boron hybrid filler;

(4) Weigh 1.2g phase change nanocapsule/boron nitride hybrid filler, 0.4g silicone rubber prepolymer, and 0.4g hydrogen-containing silicone oil.

(5) Add the weighed phase change nanocapsule/boron nitride hybrid filler silicone rubber prepolymer and hydrogen-containing silicone oil into the container and stir with a planetary mixer. The stirring program is set to 2000 rpm and the time is 3 minutes.

(6) Coat the glue obtained in step (5) into a 20×20×1mm mold, place it in a vacuum degassing barrel, and degas at 30°C and 100kPa for 20 minutes; take it out and let it stand at 25°C for 48 hours. After curing and molding, a white smooth gasket is obtained after demoulding, with a phase change enthalpy value of 54J/g, a thermal conductivity of 1.28W/(m·K), and a hardness of 40HA at room temperature (25°C).

For comparison, directly mixed nanocapsules/boron nitride fillers were prepared at the same time. The operation process was as follows: weigh 0.6g phase change nanocapsules, 0.6g boron nitride, 0.4g silicone rubber prepolymer, and 0.4g hydrogen-containing silicone oil. Place it in a planetary mixer and stir. The stirring program is set to 2000rpm and the time is 3 minutes. Coat the glue obtained in step (5) into a 20×20×1mm mold and place it in a vacuum degassing barrel at 30°C and 100kPa. Degas for 20 minutes; take it out and let it stand for 48 hours at 25°C to solidify. After demoulding, a white smooth gasket is obtained. The phase change enthalpy value is 52.3J/g, the thermal conductivity is 0.98W/(m·K), and the temperature is 0.98W/(m·K) at room temperature (25 ℃) hardness is 40.8HA.

Figure 2 is a microscopic morphology diagram of the phase change nanocapsule/boron nitride hybrid filler in Example 1. By comparison, it can be seen that the directly mixed sample pieces and balls are easy to separate, while the electrostatic self-assembled hybrid filler makes the nitride The boron sheets are tightly combined with the phase change nanocapsule balls to form a new filler structure with a lotus seed-lotus pod shape. After adding the silicone rubber matrix, as shown in Table 1, compared with the directly mixed phase change nanocapsule/boron nitride/silicone rubber composite material at this mass fraction, the silicone rubber containing phase change nanocapsule/boron nitride hybrid filler The thermal conductivity of the composite material increased by 30.61%.

The application of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler obtained in this example as a thermal interface material:

The silicone rubber composite thermal pad containing phase change nanocapsules/boron nitride hybrid filler obtained above is placed between the alumina ceramic heating plate and the five-heat pipe fin CPU radiator, as shown in Figure 3. A dual-fan forced air cooling system can also be connected to extract the heat generated during testing. The test sample is placed between the heating plate and the copper heat sink of the radiator, and is locked with screws to make them in close contact. A calibrated T-type thermocouple (temperature measurement range is -200°C ~ 350°C, tolerance value is 0.5°C) is fixed at the center point of the lower surface of the alumina ceramic heating plate, which is used to accurately monitor the temperature changes of the heating plate. Use the voltage of the DC stabilized power supply to control the heating power of the heating plate. Set the power to 18W (commercial chip heating power). Use an Agilent acquisition instrument to collect data on the thermocouple temperature at the center point of the lower surface of the alumina ceramic heating plate. Collect the temperature change curve of the thermal conductive chip after heating for 300 seconds to examine the heat dissipation effect of the thermal conductive pad. The results are shown in Figure 4. Using the silicone rubber composite thermal pad containing phase change nanocapsules/boron nitride hybrid filler as a thermal interface material is much better than using the directly mixed phase change nanocapsules/boron nitride/silicone rubber composite. The chip temperature of the material thermal pad is 24.5℃ lower. It can be seen that using the silicone rubber composite material of the phase change nanocapsule/boron nitride hybrid filler of the present invention as a thermal interface material can significantly increase the thermal conductivity, reduce the chip temperature, and improve the heat dissipation performance.

Example 2

A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, made of the following raw materials in terms of mass fraction: phase change nanocapsules/boron nitride hybrid filler 50%, polydimethyl silicon Oxane prepolymer 25% and hydrogenated siloxane 25%.

The preparation method of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler includes the following steps:

(1) Use the interfacial hydrolysis-polycondensation method to prepare phase change nanocapsules with paraffin as the core material and silica as the shell material: paraffin (15.0g), ethyl orthosilicate TEOS (7.5g) in a 250mL three-neck flask. Stir and mix at 60°C to form a transparent solution. Then, cetyltrimethylammonium bromide CTAB (0.82g), deionized water (35.5mL) and absolute ethanol (71.25mL) were added to a 250mL beaker at the same time, and kept warm to 60°C. Add the aqueous phase composed of absolute ethanol, deionized water, and CTAB to the oil phase composed of paraffin and TEOS at 60°C, and mechanically stir at 350 rpm for 4 hours to form a stable O/W emulsion. Add 1.5 mL of 25 wt% ammonia water and keep stirring at 60°C for 16 h to catalyze the interfacial hydrolysis-condensation polymerization reaction of TEOS. Finally, after filtering, washing with deionized water, washing with petroleum ether, and drying, about 8 g of white powder, namely paraffin@silica phase change nanocapsules, was obtained.

(2) Use 1mol·L ^-1 dilute sulfuric acid to adjust the pH to 3 while dispersed in 1000mL deionized water. Stir 3g sodium polystyrene sulfonate (PSS) and 10g boron nitride for 6 hours, let it stand for 12 hours and then filter to make it negatively charged. PSS is deposited on the boron nitride surface;

(3) Add 10g of the paraffin@silica phase change nanocapsules obtained in steps (1) and (2) (average particle size 900nm, phase change temperature 48°C, latent heat value 180J/ g), add 100 mL of deionized water to disperse the boron nitride deposited by negatively charged PSS, adjust the pH to 1 with hydrochloric acid to make the silica shell positively charged, stir for 8 hours, vacuum filter, and dry to obtain the phase change nanocapsules/nitrogen Boron hybrid filler;

(4) Weigh 1.0g phase change nanocapsule/boron nitride hybrid filler, 0.5g silicone rubber prepolymer, and 0.5g hydrogen-containing siloxane.

(5) Add the weighed phase change nanocapsule/boron nitride hybrid filler silicone rubber prepolymer and hydrogen-containing siloxane to the container and stir with a planetary mixer. The stirring program is set to 700 rpm and the time is 6 minutes.

(6) Coat the rubber obtained in step (5) into a 20×20×1mm mold, place it in a vacuum degassing barrel, and degas at 25°C and 80kPa for 30 minutes; take it out and let it stand at 25°C for 48 hours. After curing and molding, a white smooth gasket is obtained after demoulding. The phase change enthalpy value is 29J/g, the thermal conductivity is 1.02W/(m·K), and the hardness at normal temperature (25℃) is 50HA.

For comparison, directly mixed nanocapsules/boron nitride fillers were prepared at the same time. The operation process was as follows: weigh 0.33g phase change nanocapsules, 0.67g boron nitride, 0.5g silicone rubber prepolymer, and 0.5g hydrogen-containing silicone. Alkane, stir in a planetary mixer, set the stirring program to 700rpm, time 6min, apply the glue obtained in step (5) to a 20×20×1mm mold, place it in a vacuum degassing barrel, and heat it at 25°C , defoaming at 80kPa for 30 minutes; take it out and let it stand at 25°C for 48 hours to solidify and form. After demoulding, a white smooth gasket is obtained, with a phase change enthalpy value of 28.4J/g, a thermal conductivity of 0.92W/(m·K), and room temperature. (25℃) hardness is 50.3HA. Compared with the phase change nanocapsule/boron nitride/silicone rubber composite directly mixed at this mass fraction, the thermal conductivity of the silicone rubber composite containing phase change nanocapsule/boron nitride hybrid filler increased by 10.87%.

Application of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler obtained in this example:

The operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 10W. Test results: Using the silicone rubber composite thermal pad containing phase change nanocapsule/boron nitride hybrid filler as a thermal interface material is better than using the directly mixed phase change nanocapsule/boron nitride/silicone rubber composite thermal pad. The chip temperature is 18.7℃ lower.

Example 3

A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, made of the following raw materials in terms of mass fraction: phase change nanocapsules/boron nitride hybrid filler 10%, polydimethyl silicon Oxane prepolymer 45% and hydrogenated siloxane 45%.

The preparation method of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler includes the following steps:

(1) Use the interfacial hydrolysis-polycondensation method to prepare phase change nanocapsules with paraffin as the core material and silica as the shell material: paraffin (15.0g), ethyl orthosilicate TEOS (7.5g) in a 250mL three-neck flask. Stir and mix at 60°C to form a transparent solution. Then, cetyltrimethylammonium bromide CTAB (0.82g), deionized water (35.5mL) and absolute ethanol (71.25mL) were added to a 250mL beaker at the same time, and kept warm to 60°C. Add the aqueous phase composed of absolute ethanol, deionized water, and CTAB to the oil phase composed of paraffin and TEOS at 60°C, and mechanically stir at 350 rpm for 4 hours to form a stable O/W emulsion. Add 1.5 mL of 25 wt% ammonia water and keep stirring at 60°C for 16 h to catalyze the interfacial hydrolysis-condensation polymerization reaction of TEOS. Finally, after filtering, washing with deionized water, washing with petroleum ether, and drying, about 8 g of white powder, namely paraffin@silica phase change nanocapsules, was obtained.

(2) Use 1mol·L ^-1 dilute hydrochloric acid to adjust the pH to 3 while dispersed in 1000mL deionized water. Stir 3g sodium polystyrene sulfonate (PSS) and 10g boron nitride for 10h, let it stand for 10h and then filter to make it negatively charged. PSS is deposited on the boron nitride surface;

(3) Add 10g of the paraffin@silica shell phase change nanocapsules obtained in steps (1) and (2) in the container at a mass ratio of 2:1 (average particle size 900nm, phase change temperature 48°C, latent heat value 180J /g), negatively charged PSS deposited boron nitride, add 100 mL deionized water to disperse, adjust the pH to 5 with hydrochloric acid, make the silica shell positively charged, stir for 7 hours, vacuum filter, and dry to obtain the phase change nanocapsules/ Boron nitride hybrid filler;

(4) Weigh 0.2g phase change nanocapsule/boron nitride hybrid filler, 0.9g silicone rubber prepolymer, and 0.9g hydrogen-containing siloxane.

(5) Add the weighed phase change nanocapsule/boron nitride hybrid filler silicone rubber prepolymer and hydrogen-containing siloxane into the container and stir with a planetary mixer. The stirring program is set to 1400 rpm and the time is 5 minutes.

(6) Coat the rubber obtained in step (5) into a 20×20×1mm mold, place it in a vacuum degassing barrel, and degas at 40°C and 90kPa for 25 minutes; take it out and let it stand at 25°C for 48 hours. After curing and molding, a white smooth gasket is obtained after demoulding. The phase change enthalpy value is 12J/g, the thermal conductivity is 0.44W/(m·K), and the hardness at normal temperature (25℃) is 25HA.

For comparison, directly mixed nanocapsules/boron nitride fillers were prepared at the same time. The operation process was as follows: weigh 0.33g phase change nanocapsules, 0.67g boron nitride, 0.9g silicone rubber prepolymer, and 0.9g hydrogen-containing silicone. alkane, put it into a planetary mixer and stir, the stirring program is set to 1400rpm, time 5min, apply the rubber obtained in step (5) to a 20×20×1mm mold, place it in a vacuum degassing barrel, and heat it at 40°C , defoaming at 90kPa for 25 minutes; take it out and let it stand at 25°C for 48 hours to solidify. After demoulding, a white smooth gasket is obtained. The phase change enthalpy value is 11J/g, the thermal conductivity is 0.41W/(m·K), and the temperature is 0.41W/(m·K) at room temperature ( 25℃) hardness is 26HA. Compared with the phase change nanocapsule/boron nitride/silicone rubber composite directly mixed at this mass fraction, the thermal conductivity of the silicone rubber composite containing phase change nanocapsule/boron nitride hybrid filler increased by 7.32%.

Application of a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler obtained in this example:

The operation process is basically the same as that of Embodiment 1, except that the voltage of the DC regulated power supply is used to control the heating power of the heating plate, and the power is set to 5W. Test results: Using the silicone rubber composite thermal pad containing phase change nanocapsule/boron nitride hybrid filler as a thermal interface material is better than using the directly mixed phase change nanocapsule/boron nitride/silicone rubber composite thermal pad. The chip temperature is 9.47℃ lower.

Table 1

Table 1 is the thermal conductivity comparison data of the silicone rubber composite material containing phase change nanocapsule/boron nitride hybrid filler and the directly mixed phase change nanocapsule/boron nitride/silicone rubber composite material of Examples 1-3 of the present invention. . It can be seen that the silicone rubber composite material containing phase change capsule/boron nitride hybrid filler has a higher thermal conductivity than the directly mixed phase change capsule/boron nitride/silicone rubber composite material. In Examples 1 and 2 , 3 conditions, the thermal conductivity was increased by 30.61%, 10.87%, and 7.32% respectively, indicating that the new lotus seed-lotus pod structure formed by the hybrid filler with connected tablets and balls is beneficial to reducing the nanocapsule-boron nitride The interface thermal resistance between the composite materials significantly improves the thermal conductivity of the composite material.

Claims (7)

1. A method for preparing a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler, which is characterized by comprising the following steps: (1) Preparation of paraffin@silica phase change nanocapsules using interfacial hydrolysis-condensation polymerization method; (2) Use acid solution to adjust the pH to acidic under solvent dispersion. Stir sodium polystyrene sulfonate and boron nitride for 6 to 12 hours, let it stand for 12 to 24 hours and then filter, so that the negatively charged sodium polystyrene sulfonate is deposited in the nitrogen. boron surface; (3) Add the paraffin@silica phase change nanocapsules obtained in steps (1) and (2) and the boron nitride deposited by negatively charged sodium polystyrene sulfonate in different mass proportions in the container, add solvent to disperse, and acid solution Adjust the pH to make the silica shell positively charged, stir for 6 to 8 hours to perform the electrostatic self-assembly process, vacuum filtrate, and dry to obtain the phase change nanocapsule/boron nitride hybrid filler; (4) Add the hybrid filler, silicone rubber matrix prepolymer and curing agent obtained in step (3) to the mixer for stirring. The stirring program is set to 500~1000rpm and the time is 3~6 minutes; (5) Coat the rubber obtained in step (4) into the mold, place it in a vacuum degassing barrel, and degas it at 25°C~40°C and 80kPa~100kPa for 20~30 minutes; take it out and let it stand for solidification. After demoulding, the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler is obtained; The interfacial hydrolysis-condensation polymerization method described in step (1) is specifically: anhydrous ethanol, deionized water, and cetyldimethylammonium bromide constitute the water phase, the core material material and the shell material precursor constitute the oil phase, and the water phase and the oil phase are first fully dissolved at 60°C, and then mixed together to form a stable O/W emulsion through the emulsification process; adding ammonia initiator, the shell material precursor forms shell oligomerization through ammonia-catalyzed hydrolysis-polycondensation reaction at the interface body, and is negatively charged, which is immediately adsorbed on the surface of the positively charged micelles through electrostatic interaction. As the interface polycondensation reaction proceeds, the shell oligomers continue to migrate from the inside of the oil droplet to the interface, and finally in the core liquid The droplet surface gradually condenses to form an inorganic shell; The particle size of the paraffin@silica phase change nanocapsules described in step (1) is 800~1000nm, the phase change temperature is 42°C~48°C, and the latent heat of phase change is 120~180J/g; The solvent in step (3) is one or more of deionized water and ethanol, the acid solution in step (3) is one or more of dilute hydrochloric acid, dilute acetic acid, and dilute sulfuric acid, and the pH in step (3) is is 1 to 5, and the mass ratio used in step (3) is paraffin@silica phase change nanocapsules: boron nitride deposited by negatively charged sodium polystyrene sulfonate = 1:1 or 1:2. 2. A method for preparing a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler according to claim 1, characterized in that the solvent in step (2) is deionized water or ethanol. One or more, the acid solution in step (2) is one or more of dilute hydrochloric acid and dilute sulfuric acid. 3. A method for preparing a silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler according to claim 1, characterized in that the curing agent in step (4) is hydrogen-containing polysiloxane. alkyl. 4. The silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler prepared by the preparation method of any one of claims 1 to 3, characterized in that it includes a silicone rubber matrix and a silicone rubber composite formed based on electrostatic self-assembly. Phase change nanocapsules/boron nitride hybrid fillers. 5. A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler according to claim 4, characterized in that, in terms of mass fraction, the phase change nanocapsules/boron nitride hybrid filler is Filled silicone rubber composite materials include phase change nanocapsule/boron nitride hybrid filler 10%~60%, silicone rubber matrix prepolymer 20%~45% and curing agent 20%~45%. The sum of the above raw materials is 100%. 6. A silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler according to claim 4, characterized in that the silicone rubber containing phase change nanocapsules/boron nitride hybrid filler The phase change enthalpy value of the composite material is 29~54J/g, the thermal conductivity is 1.02~1.28W/(m∙K), and the hardness at room temperature is 40~50HA. 7. Application of the silicone rubber composite material containing phase change nanocapsules/boron nitride hybrid filler as claimed in claim 6 as a thermal interface material.