Preparation method of patterned hydrogel / boron nitride / polydimethylsiloxane heat-conducting composite material

Abstract

The invention discloses a preparation method of a patterned hydrogel / boron nitride / polydimethylsiloxane heat-conducting composite material, and aims to solve the problem that in the prior art, a large amount of heat-conducting filler needs to be added when the high heat conductivity of the composite material is realized, so that the comprehensive performance of the composite material is reduced. According to the invention, the continuous and directional hydrogel network is combined with BN / PDMS to prepare a macroscopic-microcosmic bicontinuous heat-conducting channel, so that the problem that force-heat of a heat-conducting material is difficult to coordinate is solved. The preparation method comprises the following specific steps: carrying out vacuum-assisted impregnation on vertically-oriented boron nitride aerogel (BN) and a polydimethylsiloxane (PDMS) composite material with a low crosslinking degree to prepare the BN / PDMS composite material. And the patterned hydrogel / BN / PDMS composite material is prepared by organically combining the photocuring hydrogel network and the composite material by combining a laser engraving technology. The patterned hydrogel / boron nitride / polydimethylsiloxane heat-conducting composite material prepared by the method can quickly transfer heat, and has high flexibility and variability.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible thermal interface materials, and in particular relates to a method for preparing a patterned hydrogel / boron nitride / polydimethylsiloxane thermally conductive composite material. Background Art

[0002] With the advancement of science and technology, the demand for thermal conductive materials in the fields of automobiles, new energy, electrical electronics, aerospace, microelectronics packaging, etc. is increasing. Traditional thermal conductive materials, such as ceramics, copper, etc., can no longer meet the growing demand. According to the current development status of thermal conductive composite materials, adding thermal conductive fillers is still an important method for manufacturing polymer-based thermal conductive composite materials. Adding filled thermal conductive composite materials has a great relationship with the type, compounding method and addition amount of fillers. For example, when the content of thermal conductive fillers is low, the thermal conductive fillers cannot be evenly distributed in the polymer matrix, resulting in the inability of the thermal conductive filler particles to contact each other and form a thermal conductive network structure. Therefore, the thermal conductivity of the composite material is limited. When the content of the thermal conductive filler increases to a certain extent, the thermal conductive filler particles begin to contact each other, thereby forming a thermal conductive network structure, and the thermal conductivity of the composite material increases rapidly. However, increasing the content of thermal conductive fillers can improve the thermal conductivity of the composite material to a certain extent, but it will lead to a serious deterioration of the comprehensive properties of the thermal conductive composite material such as mechanical properties and processing properties.

[0003] The "ideal" thermal interface material must have both high thermal conductivity to minimize thermal resistance, as well as high flexibility and the ability to adapt to soft and curved surfaces, while also being able to accommodate thermal stresses caused by the mismatch in thermal expansion of the two connected materials. The significance of soft elastic thermally conductive composite materials is that they provide an efficient thermal management solution while having flexible adaptability, high thermal conductivity and good mechanical properties. This makes them have broad application prospects in various fields, especially in flexible electronics and microelectronics. Therefore, how to balance the comprehensive properties of the material while obtaining good thermal conductivity is a key issue that needs to be urgently solved in the field of thermally conductive composite materials. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that a large amount of thermal conductive fillers are added to achieve high thermal conductivity of composite materials in the prior art, resulting in a significant reduction in the comprehensive properties of the composite materials such as mechanical properties and processing properties. Since hydrogels have high flexibility and variability, as well as high thermal conductivity, the hydrogel network is combined with BN / PDMS to prepare a macro-micro dual continuous thermal conductive path, which is conducive to the rapid transfer of heat.

[0005] S1, preparation of vertically oriented boron nitride aerogel. First, boron nitride nanosheets (BN) were added to 100 mL of carboxymethyl cellulose (SCMC) aqueous solution. SCMC / BN slurry was obtained by stirring the mixture for 48 hours using a ball mill. The resulting slurry was then poured into a polymethyl methacrylate mold and placed on a copper rod, partially immersed in liquid nitrogen. The sample was frozen and then freeze-dried for about 72 hours to obtain a vertically oriented boron nitride aerogel.

[0006] Furthermore, the mass of BNNS is 0.5 g to 4 g.

[0007] Furthermore, the concentration of the carboxymethyl cellulose solution is 1-2 wt.%.

[0008] Furthermore, the rotation speed of the ball mill is 100-500 rpm.

[0009] S2, preparation of boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composites. 184 Silicone rubber is a two-component kit product composed of liquid components, including a basic component and a curing agent. The basic component and the curing agent are completely mixed in a certain proportion, and an organic solvent is added to mix them evenly. The 184 precursor solution was repeatedly vacuum-assisted impregnated and heated to finally obtain the preparation of the boron nitride aerogel / polydimethylsiloxane composite material.

[0010] Further, The ratio between the basic components and the curing agent in 184 silicone rubber is (100-10):1.

[0011] Furthermore, the organic solvent is ethyl acetate, dichloromethane, etc.

[0012] Furthermore, the heating temperature is 80-120° C. and the reaction time is 6-8 h.

[0013] Furthermore, the content of boron nitride aerogel in BN / PDMS is 2.6wt.%-21.7wt%.

[0014] S3, preparation of patterned hydrogel / boron nitride / polydimethylsiloxane, using boron nitride aerogels of different densities and the above-mentioned PDMS precursors to prepare BN / PDMS composites by repeated vacuum-assisted impregnation. The resulting composite was reacted at 80°C for 24 hours. In addition, a digital laser etcher was used to etch microgrooves of different shapes on the BN / PDMS sample. After treatment with benzophenone solution, a micro-syringe was used to inject the photocurable polyacrylamide hydrogel precursor into the substrate groove, and then the hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite was patterned after irradiation with ultraviolet light.

[0015] Further microgrooves are shaped as dot array (D), line array (L) and network (N); the diameter of the dot array is 1 mm, and the width of the line array is 0.5 mm.

[0016] Further, the model of the digital laser etching machine is CMA-4030, Han's Yueming, the moving speed is 100 mm / s, and the laser power is 30W.

[0017] Furthermore, the mass fraction of the hydrogel is 15-30wt.%.

[0018] Furthermore, the concentration of benzophenone is 1-5wt.%, and the organic solvent is ethanol or ethyl acetate.

[0019] Furthermore, the photocurable hydrogel is a polyacrylic acid hydrogel.

[0020] Furthermore, preferably, the photocurable hydrogel precursor solution (23wt.% acrylamide, 0.051-0.2wt.% methacrylamide and 0.2wt.% 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetone)

[0021] Furthermore, the UV curing time is 10-20 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Scanning electron microscope image of BN

[0023] Figure 2 Scanning electron microscope image of vertically oriented boron nitride aerogel DETAILED DESCRIPTION

[0024] Embodiment 1

[0025] S1, 0.5g of boron nitride nanosheets (BN) were added to 100mL of 1wt.% carboxymethyl cellulose (SCMC) aqueous solution. The SCMC / BN slurry was obtained by stirring the mixture for 48 hours using a ball mill. The resulting slurry was then poured into a polymethyl methacrylate (PMMA) mold and placed on a copper rod, partially immersed in liquid nitrogen. The sample was frozen and then freeze-dried for about 72 hours to obtain a vertically oriented boron nitride aerogel.

[0026] S2, preparation of boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composites. 184 silicone rubber is a two-component kit product composed of liquid components, including a basic component and a curing agent. The basic component and the curing agent are mixed in a ratio of 50:1 and added to a dichloromethane solution. The precursor solution 184 was repeatedly vacuum-assisted impregnated, and the resulting composite material was reacted at 80° C. for 24 hours to prepare a boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composite material.

[0027] S3, use a digital laser etcher to etch a network-type (N) microgroove on the VGA / BPDMS sample. The model of the digital laser etcher is CMA-4030, Han's Yueming, the moving speed is 100mm / s, and the laser power is 30W. The diameter of the center point is 1mm and the width is 0.5mm. After being treated with benzophenone solution, a micro-syringe is used to inject the photocurable hydrogel precursor into the substrate groove. The hydrogel components are 23wt.% acrylamide, 0.051-0.1wt.% methacrylamide and 0.2wt.% 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetone. Then, after irradiation with ultraviolet light for 10 minutes, the patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is obtained. The thermal conductivity of the obtained patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is 0.56Wm -1 K -1 ; The maximum compression rate is 80%, and the maximum compression strain is 1.6MPa.

[0028] Embodiment 2

[0029] S1, 1g of boron nitride nanosheets (BN) were added to 100mL of 1wt.% carboxymethyl cellulose (SCMC) aqueous solution. SCMC / BN slurry was obtained by stirring the mixture for 12 hours using a ball mill. The resulting slurry was then poured into a polymethyl methacrylate (PMMA) mold and placed on a copper rod, partially immersed in liquid nitrogen. The sample was frozen and then freeze-dried for about 72 hours to obtain a vertically oriented boron nitride aerogel.

[0030] S2, preparation of boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composites. 184 silicone rubber is a two-component kit product composed of liquid components, including a basic component and a curing agent. The basic component and the curing agent are mixed in a ratio of 10:1 and added to a dichloromethane solution. The precursor solution 184 was repeatedly vacuum-assisted impregnated, and the resulting composite material was reacted at 80° C. for 24 hours to prepare a boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composite material.

[0031] S3, use a digital laser etcher to etch a network-type (L) microgroove on the VGA / BPDMS sample. The model of the digital laser etcher is CMA-4030, Han's Yueming, the moving speed is 100mm / s, and the laser power is 30W. The diameter of the center point is 1mm and the width is 0.5mm. After being treated with benzophenone solution, a micro-syringe is used to inject the photocurable hydrogel precursor into the substrate groove. The hydrogel components are 23wt.% acrylamide, 0.051wt.% methacrylamide and 0.2wt.% 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetone. Then, after irradiation with ultraviolet light for 10 minutes, the patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is obtained. The thermal conductivity of the obtained patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is 0.76Wm -1 K -1 ; The maximum compression rate is 50% and the compression stress is 1MPa.

[0032] Embodiment 3

[0033] S1, 2g of boron nitride nanosheets (BN) were added to 100mL of 2wt.% carboxymethyl cellulose (SCMC) aqueous solution. SCMC / BN slurry was obtained by stirring the mixture for 12 hours using a ball mill. The resulting slurry was then poured into a polymethyl methacrylate (PMMA) mold and placed on a copper rod, partially immersed in liquid nitrogen. The sample was frozen and then freeze-dried for about 72 hours to obtain a vertically oriented boron nitride aerogel. Preparation of boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composites.

[0034] S2, 184 silicone rubber is a two-component kit product composed of liquid components, including a basic component and a curing agent. The basic component and the curing agent are mixed in a ratio of 50:1 and added to a dichloromethane solution. The precursor solution 184 was repeatedly vacuum-assisted impregnated, and the resulting composite material was reacted at 80° C. for 24 hours to prepare a boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composite material.

[0035] S3, use a digital laser etcher to etch a network-type (N) microgroove on the VGA / BPDMS sample. The model of the digital laser etcher is CMA-4030, Han's Yueming, the moving speed is 100mm / s, and the laser power is 30W. The diameter of the center point is 1mm and the width is 0.5mm. After being treated with benzophenone solution, a micro-syringe is used to inject the photocurable hydrogel precursor into the substrate groove. The hydrogel components are 23wt.% acrylamide, 0.051wt.% methacrylamide and 0.2wt.% 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetone. Then, after irradiation with ultraviolet light for 10 minutes, the patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is obtained. The thermal conductivity of the obtained patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is 2.78Wm -1 K -1 ; The maximum compression rate is 40% and the maximum stress is 2.89MPa.

Claims

1. A method for preparing a patterned hydrogel / boron nitride / polydimethylsiloxane thermally conductive composite material, characterized in that Specific boron nitride nanosheets (BN) were added to 100 mL of a certain concentration of carboxymethyl cellulose (SCMC) aqueous solution. The SCMC / BN slurry was obtained by stirring the mixture for 12 hours using a ball mill. The resulting slurry was then poured into a polymethyl methacrylate (PMMA) mold and placed on a copper rod, partially immersed in liquid nitrogen. The sample was frozen and then freeze-dried for about 72 hours to obtain a vertically oriented boron nitride aerogel. Preparation of boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composites. 184 Silicone rubber is a two-component kit product composed of liquid components, including a basic component and a curing agent. The basic component and the curing agent are added to a dichloromethane solution in a certain proportion and mixed evenly. 184 precursor solution was repeatedly vacuum-assisted impregnated, and the resulting composite material was heated and cured to prepare a boron nitride aerogel / polydimethylsiloxane (BN / PDMS) composite material. In addition, a digital laser etching machine was used to etch a series of microgrooves of different shapes on the VGA / BPDMS sample. After the laser-engraved BN / PDMS composite material was treated with a benzophenone solution, a micro-injection was used to inject a photocurable hydrogel precursor solution into the substrate groove. The hydrogel composition was 23wt.% acrylamide, 0.051-0.1wt.% methacrylamide and 0.2wt.% 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetone. Then, after irradiation with a UV lamp for 10 minutes, the patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material was formed.

2. According to claim 1, the mass of BN is 0.5-4g, and the concentration of SCMC aqueous solution is 1-2wt.%.

3. According to claim 1, it is characterized in that: The laser engraved BN / PDMS composite material is surface treated by using a benzophenone solution, the concentration of the benzophenone solution is 1-5wt.%, and the organic solvent is ethanol or ethyl acetate.

4. According to claim 1, it is characterized in that: The photocurable hydrogel is a polyacrylic acid hydrogel.

5. According to claim 1, it is characterized in that: The mass fraction of the hydrogel in the prepared patterned hydrogel / boron nitride / polydimethylsiloxane thermal conductive composite material is 15-30wt.%.

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