CN116478449B - Preparation method and application of one-dimensional core-shell structure heat-conducting filler - Google Patents

Abstract

A preparation method and application of a one-dimensional core-shell structure thermally conductive filler, which relates to the technical field of polymer-based thermally conductive composite materials. The purpose of the present invention is to solve the problem of how to obtain a polymer-based composite material that has both thermal conductivity and insulation properties, while achieving low filling amount and excellent stability. The invention provides a method for preparing a one-dimensional core-shell structure thermally conductive filler, which adopts an electrospinning method, uses silica sol as a base material, and adjusts the content of boron nitride nanosheets to obtain high thermal conductivity one-dimensional fillers with different boron nitride contents. Fillers, compared to commercial boron nitride nanosheets, are significantly improved in both the in-plane and out-of-plane directions. The invention can obtain a preparation method and application of a one-dimensional core-shell structure thermally conductive filler.

Description

Preparation method and application of one-dimensional core-shell structure thermally conductive filler

Technical field

The invention relates to the technical field of polymer-based thermally conductive composite materials, and in particular to a preparation method and application of a one-dimensional core-shell structure thermally conductive filler.

Background technique

With the miniaturization and integration of power electronic equipment and the continuous improvement of energy density, higher requirements have been placed on the comprehensive performance of insulating packaging materials. However, the extremely low thermal conductivity of polymers (∼0.2 W/m·K) limits the heat release inside the device, which will significantly reduce the stability, reliability, and lifespan of power electronic devices. Therefore, the preparation of polymer-based composite materials with both thermal conductivity and insulation properties has become a hot research topic today. Filling thermally conductive fillers into polymers to prepare composite materials is an effective strategy to improve the thermal conductivity of polymers. Numerous studies have shown that the introduction of ceramic fillers can impart high thermal conductivity to composite materials. Traditional commercial thermally conductive fillers require a higher filling amount to satisfactorily improve the thermal conductivity of the polymer material. However, this will reduce the insulation performance and mechanical properties of the composite material. At the same time, the high price of high thermal conductivity fillers limits their promotion and application. Therefore, how to achieve materials with high thermal conductivity and excellent insulation properties at low filling content still requires further research.

Contents of the invention

The purpose of the present invention is to solve the problem of how to obtain a polymer-based composite material with both thermal conductivity and insulation properties, while achieving low filling amount and excellent stability, and to provide a preparation of a one-dimensional core-shell structure thermal conductive filler Methods and their applications.

A one-dimensional core-shell structure thermally conductive filler, consisting of boron nitride nanosheets and a silicon dioxide layer wrapped around the boron nitride nanosheets. The mass fraction of boron nitride nanosheets in the one-dimensional core-shell structure thermally conductive filler is 10 ~80%.

A method for preparing a one-dimensional core-shell structure thermally conductive filler according to the following steps:

Step 1: Mix ethyl orthosilicate, ammonia, ethanol and deionized water, and stir evenly to obtain a silica precursor sol;

Step 2: Mix polyvinyl alcohol, boron nitride nanosheets and ethanol, and stir evenly to obtain boron nitride nanosheet suspension;

Step 3: Stir the silica precursor sol in step 1 and the boron nitride nanosheet suspension in step 2 evenly to obtain a spinning solution;

Step 4: Vacuum defoaming the spinning solution in Step 3, and perform electrospinning to obtain a fiber membrane;

Step 5: Calculate and grind the fiber membrane in Step 4 to obtain a one-dimensional core-shell structure thermally conductive filler. The mass fraction of boron nitride nanosheets in the one-dimensional core-shell structure thermally conductive filler is 10%, 20% or 30%. %.

Application of a one-dimensional core-shell structure thermally conductive filler. The one-dimensional core-shell structure thermally conductive filler is used to prepare thermoplastic or thermosetting polymer composite materials. The thermosetting polymer composite material is highly thermally conductive. Epoxy resin, preparation method is as follows:

S1. Mix the epoxy resin and the curing agent at 50-80°C to obtain a mixed liquid; the epoxy resin is E51 type epoxy resin, and the curing agent is methylhexahydrophthalic anhydride;

S2. Mix the one-dimensional core-shell structure thermally conductive filler with an organic solvent, and stir for 1 to 3 hours at a speed of 500 to 1500 rpm/min to obtain a one-dimensional filler suspension; the organic solvent is ethanol or tert-butanol;

S3. Mix the one-dimensional filler suspension and the mixed liquid, stir for 1 to 3 hours at a speed of 1000 to 1500 rpm/min, vacuum defoaming and hot pressing to obtain a thermosetting polymer composite material. The thermosetting polymer composite material is The mass fraction of the one-dimensional core-shell structure thermally conductive filler in the polymer composite material is 10%, 15%, 20%, 25% or 30%.

Beneficial effects of the present invention:

(1) The present invention provides a method for preparing a one-dimensional core-shell structure thermally conductive filler, which adopts an electrospinning method, uses silica sol as the base material, and adjusts the content of boron nitride nanosheets to obtain high-performance materials with different boron nitride contents. The thermally conductive one-dimensional filler is significantly improved in both in-plane and out-of-plane directions compared to commercial boron nitride nanosheets.

The one-dimensional core-shell structure thermal conductive filler of the present invention has a higher aspect ratio and is easier to form a thermal conductive path in the polymer matrix. At the same time, it can enhance the compatibility between the thermal conductive filler and the polymer matrix and solve the problem of commercial boron nitride filler. The problem of easy agglomeration in the matrix.

(2) The one-dimensional core-shell structure thermally conductive filler provided by the present invention is suitable for preparing various forms of composite materials. Whether they are thermosetting materials or thermoplastic materials, they can have better stability and thermal conductivity while ensuring their insulation properties.

The invention can obtain a preparation method and application of a one-dimensional core-shell structure thermally conductive filler.

Description of the drawings

Figure 1 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 10wt% in Example 1;

Figure 2 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 20wt% in Example 2;

Figure 3 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 30wt% in Example 3.

Detailed ways

Specific Embodiment 1: This embodiment is a one-dimensional core-shell structure thermally conductive filler, which is composed of boron nitride nanosheets and a silicon dioxide layer wrapped around the boron nitride nanosheets. The one-dimensional core-shell structure thermally conductive filler contains nitride The mass fraction of boron nanosheets is 10-80%.

Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the particle size of the boron nitride nanosheets is 50 nm to 10 um.

Other steps are the same as the first embodiment.

Specific Embodiment Three: In this embodiment, a method for preparing a one-dimensional core-shell structure thermally conductive filler is carried out according to the following steps:

Step 1: Mix ethyl orthosilicate, ammonia, ethanol and deionized water, and stir evenly to obtain a silica precursor sol;

Step 2: Mix polyvinyl alcohol, boron nitride nanosheets and ethanol, and stir evenly to obtain boron nitride nanosheet suspension;

Step 3: Stir the silica precursor sol in step 1 and the boron nitride nanosheet suspension in step 2 evenly to obtain a spinning solution;

Step 4: Vacuum defoaming the spinning solution in Step 3, and perform electrospinning to obtain a fiber membrane;

Step 5: Calculate and grind the fiber membrane in Step 4 to obtain a one-dimensional core-shell structure thermally conductive filler. The mass fraction of boron nitride nanosheets in the one-dimensional core-shell structure thermally conductive filler is 10%, 20% or 30%. %.

Beneficial effects of this implementation:

(1) This embodiment provides a method for preparing a one-dimensional core-shell structure thermally conductive filler, which adopts the electrospinning method, uses silica sol as the base material, and adjusts the content of boron nitride nanosheets to obtain different boron nitride contents. High thermal conductivity one-dimensional filler, compared with commercial boron nitride nanosheets, is significantly improved in both the in-plane and out-of-plane directions.

The one-dimensional core-shell structure thermally conductive filler in this embodiment has a higher aspect ratio, which makes it easier to form a thermally conductive path in the polymer matrix. At the same time, the compatibility between the thermally conductive filler and the polymer matrix can be enhanced, solving the problem of commercial boron nitride filler. The problem of easy agglomeration in the matrix.

(2) The one-dimensional core-shell structure thermally conductive filler provided by this embodiment is suitable for preparing various forms of composite materials. Whether they are thermosetting materials or thermoplastic materials, they can have better stability and thermal conductivity while ensuring their insulation properties. .

Specific embodiment four: The difference between this embodiment and the third embodiment is: in step one, the volume ratio of ethyl orthosilicate, ammonia water, ethanol and deionized water is (10~15): (15~30): (15 ~30): (5~10), the concentration of the ethyl orthosilicate is 0.1~4mol/L, the concentration of the ammonia solution is 0.5~2mol/L, and the concentration of the ethanol is 5~20mol/ L.

Other steps are the same as the third embodiment.

Specific Embodiment 5: The difference between this embodiment and Specific Embodiment 3 or 4 is that the mass ratio of polyvinyl alcohol, boron nitride nanosheets and ethanol in step two is 3:1: (5-10).

Other steps are the same as the third or fourth embodiment.

Specific Embodiment Six: The difference between this embodiment and one of Specific Embodiments Three to Five is that the mass ratio of the silicon dioxide precursor sol and the boron nitride nanosheet suspension in step three is 1: (2-10) .

Other steps are the same as specific embodiments three to five.

Specific Embodiment Seven: The difference between this embodiment and one of Specific Embodiments Three to Six is: the stirring time in step one is 3 to 8 hours, the stirring time in step two is 1 to 3 hours, and the stirring time in step three is 3~8h.

Other steps are the same as specific embodiments three to six.

Specific Embodiment 8: The difference between this embodiment and one of Specific Embodiments 3 to 7 is that in step four, an electrospinning machine is used for electrospinning. The spinning parameters are as follows: the inner diameter of the stainless steel needle is 0.17~3.5mm; the positive plate voltage The voltage of the negative plate is 5~30kV; the needle translation speed is 50~100mm/min; the injection speed is 0.3~1mm/s, and the receiving distance is 15~25cm.

Other steps are the same as specific implementation modes three to seven.

Specific embodiment nine: The difference between this embodiment and one of specific embodiments three to eight is: after electrospinning in step four, it is dried in an oven at 60 to 100°C for 1 to 3 hours; the calcining step in step five is as follows: First, heat up to 400~600°C at a heating rate of 5~15°C/min, and keep it at 400~600°C for 0.5~2h; after the insulation, continue to heat up to 600~1300°C at a heating rate of 5~15°C/min. , and keep it at 600~1300℃ for 2~4h.

Other steps are the same as specific embodiments three to eight.

Specific Embodiment 10: This embodiment uses an application of a one-dimensional core-shell structure thermally conductive filler. The one-dimensional core-shell structure thermally conductive filler is used to prepare thermoplastic or thermosetting polymer composite materials. The thermosetting Type polymer composite material is high thermal conductivity epoxy resin, and the preparation method is as follows:

S1. Mix the epoxy resin and the curing agent at 50-80°C to obtain a mixed liquid; the epoxy resin is E51 type epoxy resin, and the curing agent is methylhexahydrophthalic anhydride;

S2. Mix the one-dimensional core-shell structure thermally conductive filler with an organic solvent, and stir for 1 to 3 hours at a speed of 500 to 1500 rpm/min to obtain a one-dimensional filler suspension; the organic solvent is ethanol or tert-butanol;

S3. Mix the one-dimensional filler suspension and the mixed liquid, stir for 1 to 3 hours at a speed of 1000 to 1500 rpm/min, vacuum defoaming and hot pressing to obtain a thermosetting polymer composite material. The thermosetting polymer composite material is The mass fraction of the one-dimensional core-shell structure thermally conductive filler in the polymer composite material is 10%, 15%, 20%, 25% or 30%.

The following examples are used to verify the beneficial effects of the present invention:

Example 1: A method for preparing a one-dimensional core-shell structure thermally conductive filler, proceed as follows:

Step 1: Place 15 mL of ethyl orthosilicate, 30 mL of ammonia, 30 mL of ethanol and 10 mL of deionized water in a beaker. After stirring for 8 hours, a silica precursor sol is obtained;

The concentration of ethyl orthosilicate is 0.2 mol/L, the concentration of ammonia water is 0.8 mol/L, and the concentration of ethanol is 10 mol/L.

Step 2: Add 18g polyvinyl alcohol, 6g boron nitride nanosheets and 36g ethanol into a new beaker, stir for 3 hours until uniform, and obtain boron nitride nanosheet suspension;

The particle size of the boron nitride nanosheets is 50nm-10um.

Step 3: Take equal masses of silica precursor sol and boron nitride nanosheet suspension, and stir for 8 hours to obtain a spinning solution.

Step 4: After vacuum defoaming the spinning solution, use a 10mL syringe to extract it and start spinning. Turn on the voltage, connect one end to the receiver aluminum foil (negative pole), and the other end to the syringe needle (positive pole) used for electrospinning, and conduct electrostatic Spinning to obtain fiber membrane;

Electrospinning uses an electrospinning machine, and the spinning parameters are as follows: the inner diameter of the stainless steel needle is 0.21mm; the voltage is 20kV (negative voltage -5kV, positive voltage 15kV); the needle translation speed is 60mm/min; the injection speed is 0.3mm/ s, the receiving distance is 25cm.

Step 5: After spinning, remove the precursor fiber membrane from the aluminum foil and dry it in an oven at 100°C for 1 hour to evaporate the remaining solvent; then place it in a muffle furnace, first at 15°C/min. The heating rate is increased to 500°C, and the temperature is maintained at 500°C for 2 hours; after the insulation is completed, the temperature is continued to be heated to 1200°C at a heating rate of 15°C/min, and maintained at 1200°C for 4 hours, and finally ground to obtain a one-dimensional core-shell structure for thermal conductivity. The filler, the mass fraction of boron nitride nanosheets is 10%, named SiO ₂ @BNNS10wt%.

Example 2: This example provides the preparation of a one-dimensional core-shell structure thermally conductive filler. The method steps are the same as Example 1. The difference is that the mass of boron nitride added in step two is 9g; the injection speed in step four is is 0.4mm/min, the receiving distance is 25cm, and the voltage is 24kV (negative voltage -12kV, positive voltage +12kV). The content of boron nitride in the finally obtained one-dimensional core-shell structure thermal conductive filler is 20wt%, named SiO ₂ @BNNS 20wt%.

Example 3: This example provides the preparation of a one-dimensional core-shell structure thermally conductive filler. The method steps are the same as Example 1. The difference is that the mass of boron nitride added in step two is 13g; the injection speed in step four is 0.5mm/min, the receiving distance is 25cm, the voltage is 26kV (negative voltage -13kV, positive voltage 13kV), the content of boron nitride in the finally obtained one-dimensional core-shell structure thermal conductive filler is 30wt%, named SiO ₂ @BNNS 30wt%.

Embodiment 4: This embodiment provides the preparation of a highly thermally conductive epoxy resin, including the following steps:

S1. Mix E51 epoxy resin and methylhexahydrophthalic anhydride curing agent at 60°C to obtain a mixed solution;

S2. Weigh the SiO ₂ @BNNS 10wt% prepared in Example 1 to be 2.47g, 3.924g, 5.559g, 7.412g and 8.52g (i.e. the mass proportion of SiO ₂ @BNNS 10wt% in the high thermal conductive epoxy resin (10wt%, 15wt%, 20wt%, 25wt% and 30wt% respectively) were stirred with absolute ethanol at a speed of 1500rpm/min for 3h to obtain a one-dimensional filler suspension;

S3. Mix the one-dimensional filler suspension and the mixed liquid, stir for 1 to 3 hours at a speed of 1000 to 1500 rpm/min, transfer to a vacuum oven for vacuum defoaming, and then perform hot pressing to obtain a thermosetting polymer composite material. .

Comparative example 1:

This comparative example provides a preparation of pure epoxy resin. The method steps are the same as in Example 4. The only difference is that the amount of SiO2@BNNS 10wt% is 0g. Pure epoxy resin is obtained, and its performance parameters are shown in Table 1. .

Comparative example 2:

This comparative example provides a preparation of a flexible thermally conductive film. The method steps are the same as in Example 4. The only difference is that the amounts of two-dimensional boron nitride nanoparticles used are 2.47g, 3.924g, 5.559g, 7.412g and 8.52g respectively. The sheets were used to replace 10wt% of SiO2@BNNS prepared in Example 1 to obtain a high thermal conductive epoxy resin, whose performance parameters are shown in Table 1.

Table 1 shows the performance parameters of the high thermal conductivity epoxy resin obtained in this example;

Table 1

Table 1 is a comparison table of performance data between high thermal conductivity epoxy resin made with SiO ₂ @BNNS 10wt% as filler and high thermal conductivity epoxy resin made with two-dimensional boron nitride nanosheets as filler. As shown in Table 1, all filling amounts of the next-dimensional filler SiO ₂ @BNNS 10wt% are used as high thermal conductivity epoxy resins as thermal conductive fillers. Compared with boron nitride nanosheets, their in-plane and out-of-plane thermal conductivity have different thermal conductivity coefficients. It can be improved and still maintain good insulation properties, so it is more suitable as a thermal conductive filler for various materials, which can further improve the thermal conductivity of polymer materials.

Figure 1 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 10wt% in Example 1. Figure 2 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 20wt% in Example 2. Figure 3 is a scanning electron microscope image of the one-dimensional core-shell structure thermally conductive filler SiO ₂ @BNNS 30wt% in Example 3.

As shown in Figure 1-3, it can be noticed that the SiO ₂ @BNNS fibers are uniform and have a high aspect ratio. As the h-BN content in SiO ₂ @BNNS fibers increases, the fiber diameter of SiO ₂ @BNNS gradually increases. At the same time, as the BNNS content of the calcined SiO ₂ @BNNS fiber increases, the shape of the fiber becomes less regular, and more and more BNNS appear on the surface of the fiber, increasing the roughness of the fiber. Moreover, the high aspect ratio SiO ₂ @BNNS thermally conductive filler is easier to form a thermal conductive path in the polymer matrix, and at the same time can enhance the compatibility between the thermally conductive filler and the polymer matrix, solving the problem that commercial boron nitride filler is easy to agglomerate in the matrix. question.

Claims (9)

1. A one-dimensional core-shell structure thermally conductive filler, characterized in that the one-dimensional core-shell structure thermally conductive filler is composed of boron nitride nanosheets and a silicon dioxide layer wrapped outside the boron nitride nanosheets. The one-dimensional core The mass fraction of boron nitride nanosheets in the shell structure thermally conductive filler is 10 to 80%, and the particle size of the boron nitride nanosheets is 50 nm to 10um. 2. The preparation method of a one-dimensional core-shell structure thermally conductive filler as claimed in claim 1, characterized in that the preparation method is carried out according to the following steps: Step 1: Mix ethyl orthosilicate, ammonia, ethanol and deionized water, and stir evenly to obtain a silica precursor sol; Step 2: Mix polyvinyl alcohol, boron nitride nanosheets and ethanol, and stir evenly to obtain boron nitride nanosheet suspension; Step 3: Stir the silica precursor sol in step 1 and the boron nitride nanosheet suspension in step 2 evenly to obtain a spinning solution; Step 4: Vacuum defoaming the spinning solution in Step 3, and perform electrospinning to obtain a fiber membrane; Step 5: Calculate and grind the fiber membrane in Step 4 to obtain a one-dimensional core-shell structure thermally conductive filler. The mass fraction of boron nitride nanosheets in the one-dimensional core-shell structure thermally conductive filler is 10%, 20% or 30%. %. 3. A method for preparing a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that the volume ratio of ethyl orthosilicate, ammonia water, ethanol and deionized water in step one is (10~15): (15~30): (15~30): (5~10), the concentration of the ethyl orthosilicate is 0.1~4mol/L, the concentration of the ammonia water is 0.5~2mol/L, the The concentration of ethanol is 5~20mol/L. 4. The preparation method of a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that the mass ratio of polyvinyl alcohol, boron nitride nanosheets and ethanol in step two is 3:1: (5~ 10). 5. The preparation method of a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that the mass ratio of the silicon dioxide precursor sol and the boron nitride nanosheet suspension in step three is 1: ( 2~10). 6. A method for preparing a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that the stirring time in step one is 3~8h, the stirring time in step two is 1~3h, and in step three The stirring time is 3~8h. 7. A method for preparing a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that the electrospinning in step four adopts an electrostatic spinning machine, and the spinning parameters are as follows: the inner diameter of the stainless steel needle is 0.17~3.5mm. ; The positive plate voltage is 5~30kV, the negative plate voltage is 5~30kV; the needle translation speed is 50~100mm/min; the bolus speed is 0.3~1mm/s, and the receiving distance is 15~25cm. 8. A method for preparing a one-dimensional core-shell structure thermally conductive filler according to claim 2, characterized in that after electrospinning in step four, it is placed in an oven at 60 to 100°C for drying for 1 to 3 hours; in step five, The calcination steps are as follows: first heat up to 400~600°C at a heating rate of 5~15°C/min, and keep it at 400~600°C for 0.5~2 h; after the insulation, continue to heat up at a heating rate of 5~15°C/min. to 600~1300℃, and keep at 600~1300℃ for 2~4 hours. 9. The application of a one-dimensional core-shell structure thermally conductive filler as claimed in claim 1, characterized in that the one-dimensional core-shell structure thermally conductive filler is used to prepare thermoplastic or thermosetting polymer composite materials, so The preparation method of the thermosetting polymer composite material is as follows: S1. Mix the epoxy resin and the curing agent at 50~80°C to obtain a mixed liquid; the epoxy resin is E51 type epoxy resin, and the curing agent is methylhexahydrophthalic anhydride; S2. Mix the one-dimensional core-shell structure thermally conductive filler with an organic solvent, and stir for 1 to 3 hours at a speed of 500 to 1500 rpm/min to obtain a one-dimensional filler suspension; the organic solvent is ethanol or tert-butanol; S3. Mix the one-dimensional filler suspension and the mixed liquid, stir for 1 to 3 hours at a speed of 1000 to 1500 rpm/min, vacuum defoaming and hot pressing to obtain a thermosetting polymer composite material. The thermosetting polymer composite material The mass fraction of the one-dimensional core-shell structure thermally conductive filler in the polymer composite is 10%, 15%, 20%, 25% or 30%.