CN114854177B

CN114854177B - Nonlinear conductive epoxy resin composite material and preparation method and application thereof

Info

Publication number: CN114854177B
Application number: CN202210446471.XA
Authority: CN
Inventors: 徐华松; 苟彬; 谢从珍; 周建港
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2022-04-26
Filing date: 2022-04-26
Publication date: 2022-12-16
Anticipated expiration: 2042-04-26
Also published as: CN114854177A

Abstract

The invention discloses a nonlinear conductive epoxy resin composite material and a preparation method and application thereof. An epoxy resin composite material comprises the following components: the material comprises cellulose aerogel, epoxy resin, a curing agent and an accelerator, wherein the cellulose aerogel is loaded with modified silicon carbide; the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide is coupling agent modified silicon carbide. The epoxy resin composite material realizes a lower switching field threshold value and a higher nonlinear index, and realizes the cooperative optimization of field conductance nonlinearity and thermal conductivity.

Description

Nonlinear conductive epoxy resin composite material and preparation method and application thereof

Technical Field

The invention relates to the technical field of materials, in particular to a nonlinear conductive epoxy resin composite material and a preparation method and application thereof.

Background

Epoxy resins have advantages in electrical and mechanical properties, making them one of the main materials used in insulating structures for a variety of electrical devices. With the continuous improvement of voltage grades, electric field distortion, partial discharge and the like are more prone to occur in the insulation of high-voltage electrical equipment such as insulators, cable accessories, transistors and the like, and the degradation and breakdown failure of insulating polymer materials are caused. In order to suppress local electric field distortion and optimize electric field distribution, two methods are generally adopted, one is structural field grading, for example, the shape of an electrode is changed, and a multilayer parallel capacitor or a grading ring is added in an insulating medium; the other is an electric field gradient material prepared by blending a polymer material and a wide bandgap semiconductor filler. Compared with the structural field grading, the preparation of the composite material with the electric field gradient is simpler and more applicable.

In recent years, researchers have been working on the preparation of electric field gradient composites. In order to realize excellent nonlinear electrical conductivity in the polymer/semiconductor composite material, a large amount of fillers are required to be doped in the polymer matrix, and the doping amount is up to 30%, so that although the switching field threshold can be reduced, the excessive fillers can generate larger interface thermal resistance, reduce the thermal conductivity of the composite material and obviously reduce the service life of electrical equipment. Therefore, it is important to synergistically improve the thermal conductivity while maintaining excellent nonlinear electrical conductivity characteristics.

Disclosure of Invention

In order to overcome the problem that the epoxy resin composite material cannot maintain excellent nonlinear electrical conductivity and simultaneously has high thermal conductivity in the prior art, the invention aims to provide an epoxy resin composite material, the invention aims to provide a preparation method of the epoxy resin composite material, and the invention aims to provide application of the epoxy resin composite material.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides an epoxy resin composite material in a first aspect, which comprises the following components: the modified silicon carbide-loaded cellulose aerogel, epoxy resin, a curing agent and an accelerator; the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide is coupling agent modified silicon carbide.

Preferably, in the epoxy resin composite material, the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide is silane coupling agent modified silicon carbide; amino groups are grafted onto the silicon carbide by means of a silane coupling agent.

Preferably, the epoxy resin composite material comprises the following components in parts by mass: 15-50 parts of modified silicon carbide-loaded cellulose aerogel, 80-120 parts of epoxy resin, 80-110 parts of curing agent and 0.5-2 parts of accelerator.

Preferably, in the epoxy resin composite material, the mass of the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide is 1-30% of the mass of the epoxy resin composite material; more preferably, the mass of the modified silicon carbide in the modified silicon carbide-loaded cellulose aerogel is 4-30% of the mass of the epoxy resin composite material.

Preferably, the volume content of the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide in the epoxy resin composite material is more than 4%, and the volume content can be calculated by the true density of the silicon carbide.

Preferably, in the epoxy resin composite material, the epoxy resin is at least one of bisphenol a type epoxy resin and alicyclic epoxy resin.

Preferably, in the epoxy resin composite material, the curing agent is at least one of methyl hexahydrophthalic anhydride and methyl tetrahydrophthalic anhydride; other suitable curing agents may be selected by those skilled in the art depending on the application.

Preferably, in the epoxy resin composite material, the accelerator is at least one of DMP30, triethylamine and 2-ethyl 4-methylimidazole; other suitable promoters may be selected by those skilled in the art depending on the actual circumstances.

Preferably, the preparation method of the epoxy resin composite material, namely the cellulose aerogel loaded with the modified silicon carbide comprises the following steps:

(1) Dispersing the modified silicon carbide in water, adding cellulose, naOH and urea, mixing, and stirring the mixture;

(2) Degassing the mixture after stirring, and heating for crosslinking;

(3) And after the crosslinking is finished, obtaining the cellulose hydrogel loaded with the modified silicon carbide, and drying to obtain the cellulose aerogel loaded with the modified silicon carbide.

Preferably, in the preparation method of the modified silicon carbide-loaded cellulose aerogel, in the step (1), the mass ratio of the modified silicon carbide to the cellulose is 1: (2-5).

Preferably, in the preparation method of the cellulose aerogel loaded with the modified silicon carbide, in the step (1), the modified silicon carbide is ultrasonically dispersed in water; further preferably, the ultrasonic time is 0.5-1.5h; still more preferably, the time of sonication is 0.8-1.2h.

Preferably, the preparation method of the cellulose aerogel loaded with the modified silicon carbide comprises the steps of (1), stirring at-20 to-8 ℃; further preferably, in the step (1), the stirring is carried out at-15 ℃ to-10 ℃.

Preferably, in the preparation method of the cellulose aerogel loaded with the modified silicon carbide, in the step (2), centrifugal degassing is adopted; further preferably, the centrifugal rotating speed is 1000-1500r/min; still more preferably, the time of centrifugation is 10-15min.

Preferably, the preparation method of the cellulose aerogel loaded with the modified silicon carbide comprises the step (2) of heating and crosslinking at the temperature of 50-70 ℃; further preferably, in the step (2), the temperature for heating and crosslinking is 55-65 ℃; still more preferably, in the step (2), the temperature for the thermal crosslinking is 60 ℃.

Preferably, in the preparation method of the modified silicon carbide-loaded cellulose aerogel, in the step (2), the heating and crosslinking time is 5-7h; further preferably, the time for heating and crosslinking is 5.5-6.5h; still more preferably, the time for heat crosslinking is 6 hours.

Preferably, in the preparation method of the modified silicon carbide supported cellulose aerogel, in the step (3), the drying is freeze drying; further preferably, the temperature of freeze drying is-60 ℃ to-40 ℃; still more preferably, the temperature of freeze-drying is from-55 ℃ to-45 ℃.

Preferably, in the preparation method of the modified silicon carbide supported cellulose aerogel, in the step (3), the drying time is 48-72h.

Preferably, the preparation method of the modified silicon carbide-loaded cellulose aerogel comprises the following steps in step (1):

(1) Dispersing SiC in an alkali solution, carrying out ultrasonic treatment and stirring treatment, and filtering to obtain hydroxylated SiC;

(2) Dispersing hydroxylated SiC in an alcohol solution, adding a coupling agent, and carrying out condensation reflux reaction;

(3) And (3) filtering the mixture reacted in the step (2) to obtain the modified silicon carbide.

Preferably, in the preparation method of the modified silicon carbide, in the step (1), siC is micron silicon carbide; further preferably, the particle size of SiC is 1 to 100 μm; still more preferably, the particle size of SiC is 1 to 50 μm; more preferably, the SiC has a particle size of 1 to 20 μm.

Preferably, in the preparation method of the modified silicon carbide, in the step (1), the alkali solution is a sodium hydroxide solution; further preferably, the concentration of the sodium hydroxide solution is 0.5-1.5mol/L; still more preferably, the concentration of the sodium hydroxide solution is 0.8 to 1.2mol/L.

Preferably, in the preparation method of the modified silicon carbide, in the step (1), the ultrasonic time is 20-40min; further preferably, the time of ultrasonic treatment is 25-35min; still more preferably, the time of sonication is 30min.

Preferably, in the preparation method of the modified silicon carbide, in the step (1), the stirring temperature is 70-90 ℃; further preferably, the stirring temperature is 75-85 ℃; still more preferably, the temperature of stirring is 80 ℃.

Preferably, in the preparation method of the modified silicon carbide, in the step (1), the stirring time is 20-28h; further preferably, the stirring time is 22-26h; still more preferably, the stirring time is 24 hours.

Preferably, in the preparation method of the modified silicon carbide, in the step (2), the mass ratio of the hydroxylated SiC to the coupling agent is (2-5): 1.

preferably, in the preparation method of the modified silicon carbide, in the step (2), hydroxylated SiC is ultrasonically dispersed in an alcohol solution; further preferably, the time of ultrasonic treatment is 0.5-2h; still further preferably, the time of ultrasonic treatment is 0.8-1.5h; still more preferably, the time of sonication is 1h.

Preferably, in the preparation method of the modified silicon carbide, in the step (2), the condensation reflux reaction temperature is 70-90 ℃; further preferably, the condensation reflux reaction temperature is 75-85 ℃; still more preferably, the reaction temperature is 80 ℃ under reflux.

Preferably, the preparation method of the modified silicon carbide further comprises a drying step after washing the solid obtained after filtering in the step (3).

The invention provides a preparation method of the epoxy resin composite material, which comprises the following steps:

(1) Mixing the curing agent, the accelerator and the epoxy resin, stirring and degassing; adding cellulose aerogel loaded with modified silicon carbide, and drying the mixture to obtain an impregnated epoxy composite material;

(2) And carrying out stepped heating curing molding on the impregnated epoxy composite material to obtain the epoxy resin composite material.

Preferably, in the preparation method of the epoxy resin composite material, in the step (1), the degassing time is 6-12h.

Preferably, in the preparation method of the epoxy resin composite material, in the step (2), the gradient temperature rise curing specifically comprises the following steps: curing at 90-100 deg.C for 1-2 hr, curing at 110-120 deg.C for 2-4 hr, and curing at 130-135 deg.C for 1-2 hr.

The third aspect of the invention provides the application of the epoxy resin composite material in an electric field gradient material.

The invention has the beneficial effects that:

the epoxy resin composite material realizes a lower switching field threshold value and a higher nonlinear index, and realizes the cooperative optimization of field conductance nonlinearity and thermal conductivity.

The epoxy resin composite material comprises the components of the cellulose aerogel loaded with the modified silicon carbide, epoxy resin, a curing agent and an accelerator, and on one hand, the cellulose aerogel loaded with the modified silicon carbide is used as a cellulose framework to provide a 3D interconnection network, so that the permeation threshold of the composite material is remarkably reduced, the content of the modified silicon carbide is reduced, and the obvious field conductance nonlinear characteristic can be presented when the content of the modified silicon carbide is low. On the other hand, the cellulose aerogel loaded with the modified silicon carbide is used as a cellulose framework, the cellulose framework provides a 3D interconnection network, and the modified silicon carbide loaded on the 3D framework forms a high-efficiency heat conduction path, so that the heat loss caused by interface thermal resistance is reduced, the heat conduction path is shortened, and the heat conductivity coefficient of the epoxy resin composite material is remarkably improved.

According to the epoxy resin composite material, the cellulose aerogel loaded with the modified silicon carbide in the components is grafted with the coupling agent on the surface of the silicon carbide, so that the interface bonding force can be enhanced, covalent connection is formed between the cellulose aerogel and an epoxy group, the interface compatibility of the silicon carbide and an epoxy resin matrix is improved, the interface phonon scattering effect and the interface thermal resistance are obviously reduced, and the thermal conductivity coefficient is improved.

Drawings

FIG. 1 is a schematic view of a process for preparing an epoxy resin composite according to an embodiment.

FIG. 2 is an infrared spectrum of SiC particles and SiC-OH, modified silicon carbide (SiC-APTES) of example 1.

FIG. 3 shows the X-ray photoelectron spectroscopy spectra of SiC particles and SiC-OH, modified silicon carbide (SiC-APTES) of example 1.

FIG. 4 shows X-ray photoelectron spectroscopy (N1 s) spectra of SiC-OH and modified silicon carbide (SiC-APTES) of the SiC particles and example 1.

FIG. 5 shows a modified silicon carbide-supporting cellulose aerogel (3D) obtained in example 1 _c -SiC ₁₅ APTES).

Fig. 6 is a scanning electron microscope image of the pure cellulose aerogel of example 2.

FIG. 7 shows an epoxy resin composite material (EP/3D) of example 1 _c -SiC ₁₅ APTES).

FIG. 8 shows an epoxy resin composite material (EP/3D) of example 2 _c ) Scanning electron micrograph (c).

FIG. 9 is the switching field threshold E for the epoxy resin composites and neat epoxy prepared in examples 11-13 _c And a non-linear exponential beta plot.

FIG. 10 is the switch field threshold E of the epoxy resin composites prepared in examples 1-6 _c And a non-linear exponential beta plot.

FIG. 11 is a graph of the thermal conductivity of epoxy resin composites prepared in examples 1-11.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The examples are described only for the purpose of facilitating understanding of the present invention and are not intended to limit the scope of the present invention. The materials, reagents and the like used in the examples are those commercially available, unless otherwise specified.

Example 1

The preparation of the epoxy resin composite material, which comprises the preparation of modified silicon carbide, the preparation of cellulose aerogel loaded with modified silicon carbide and the preparation of the epoxy resin composite material, is carried out by adopting the preparation process of the epoxy resin composite material shown in the attached figure 1, and the preparation method comprises the following steps.

The preparation method of the modified silicon carbide of the embodiment is as follows:

(1) Dispersing SiC particles in a sodium hydroxide (NaOH) aqueous solution, carrying out ultrasonic treatment, and then uniformly stirring in a constant-temperature magnetic stirrer;

(2) Carrying out suction filtration on the solution through a Buchner funnel to obtain hydroxylated SiC (named SiC-OH), alternately washing the solution for 3 times by using absolute ethyl alcohol and deionized water, and then placing the washed solution in an oven for heating and drying to obtain SiC-OH particles;

(3) Ultrasonically dispersing SiC-OH particles in an ethanol water solution, then adding a silane coupling agent KH550 (APTES), and placing in an oil bath pan for condensation reflux reaction;

(4) And (3) carrying out suction filtration on the solution through a Buchner funnel, washing the solution for multiple times by using deionized water, and carrying out vacuum freeze drying to obtain APTES modified SiC particles, namely modified silicon carbide (named as SiC-APTES).

In the step (1), the mass of SiC particles is 2g, the particle size is 5 microns, the volume of NaOH solution is 200mL, the concentration is 1mol/L, the ultrasonic treatment time is 30 minutes, the constant-temperature magnetic stirring temperature is 80 ℃, and the stirring reaction time is 24 hours;

in the step (2), the drying temperature is 100 ℃ and the drying time is 12 hours.

In the step (3), the volume-to-mass ratio of APTES, absolute ethyl alcohol and SiC-OH is 1mL:180mL:3g, the ultrasonic treatment time is 1 hour, the condensation reflux reaction temperature is 80 ℃, and the ethanol water solution is obtained by mixing 180mL of absolute ethanol and 20mL of deionized water.

In the step (4), the freeze drying temperature is-50 ℃, the pressure is 0.0001Pa, the drying time is 24 hours, and the mass ratio of the obtained SiC-APTES to the SiC particles is 1.01.

The infrared spectrogram of the SiC particles and the prepared SiC-OH and modified silicon carbide (SiC-APTES) is shown in the attached figure 2. As can be seen from FIG. 2, siC was at 822cm ^-1 A strong infrared characteristic peak is positioned, and corresponds to a Si-C stretching vibration peak. Since untreated SiC does not have hydroxyl groups for functionalization, siC first needs to be hydroxylated, as SiC-OH at 3200-3700cm ^-1 Shown as the infrared peak at (a). The infrared spectroscopy of SiC-APTES proves the successful grafting of silane molecules on the SiC-OH surface. SiC-APTES in 1291, 1612 and 2920m, in contrast to SiC-OH ^-1 Three new absorption peaks appeared, which are respectively attributed to the C-N stretching vibration peak, the N-H bending vibration peak and the C-H stretching vibration peak of the alkyl group, and the results all prove that APTES is successfully grafted on the SiC surface.

To further demonstrate the successful grafting of the silane coupling agent, the composition of the surface elements of SiC-APTES was analyzed using XPS. The results are shown in FIGS. 3 to 4, and it can be seen from FIGS. 3 to 4 that SiC-APTES can clearly detect the occurrence of a new N1s peak as compared with SiC and SiC-OH, which also indicates that the silane coupling agent has been successfully grafted to the surface of the SiC particles.

The preparation method of the modified silicon carbide-loaded cellulose aerogel of the embodiment is as follows:

1) Ultrasonically dispersing the prepared SiC-APTES particles in deionized water, adding cellulose powder, naOH solid particles and urea, mixing, and mechanically stirring at low temperature until the cellulose powder is completely dissolved;

2) Placing the mixture in a high-speed centrifuge for centrifugal degassing, transferring the mixture into a sealed mould, and placing the sealed mould in a constant temperature box for heating and crosslinking;

3) After crosslinking is finished, repeatedly washing the cellulose hydrogel with deionized water for a plurality of times to obtain the cellulose hydrogel loaded with the modified silicon carbide; finally, the hydrogel was freeze-dried to obtain a modified silicon carbide-loaded cellulose aerogel (designated 3D) _c -SiC ₁₅ APTES, where 15 denotes the mass of the SiC-APTES particles, g).

In the step 1), the ultrasonic treatment time is 1 hour, the mechanical stirring temperature is-12 ℃, and the dosages of the SiC-APTES particles, the cellulose powder, the NaOH solid particles, the urea and the deionized water are 15g, 6g, 7g, 12g and 71g.

In the step 2), the centrifugation speed is 1000-1500r/min, the centrifugation time is 10-15 minutes, the temperature of the thermostat is 60 ℃, and the heating crosslinking time is 6 hours.

In step 3), the freeze drying temperature is-50 deg.C, the pressure is 0.0001Pa, the drying time is 48-72 hr, and the obtained 3D is obtained _c The mass of the-SiC-APTES is 21g.

The scanning electron microscope image of the cellulose aerogel loaded with modified silicon carbide prepared above is shown in fig. 5. As shown in FIG. 5, 3D due to the doping of SiC-APTES particles, compared to pure cellulose aerogel (shown in FIG. 6) _c -SiC ₁₅ The pore size of APTES aerogel skeleton is significantly increased due to the relatively large grain size (5 μm) of SiC-APTES, resulting in expansion of the cellulose aerogel pores. As the loading increases, more SiC-APTES particles occupy the pores and come closer to each other, which determines the formation of conductive paths, and this uniformly dispersed and interconnected SiC-APTES can lower the switching field threshold and increase the nonlinear coefficient of the polymer composite.

The preparation method of the epoxy resin composite material of the embodiment is as follows:

s1, adding a curing agent and an accelerator into epoxy resin, continuously stirring at room temperature, transferring the mixture into a vacuum stirrer, stirring and vacuum degassing;

s2, preparing the 3D _c -SiC ₁₅ The APTES skeleton is immersed in the epoxy resin until complete penetration. Then transferring the mixture into a vacuum drying oven, and continuously vacuumizing at room temperature;

s3, placing the impregnated epoxy composite material in a stainless steel mold for stepped heating curing molding to obtain the epoxy resin composite material (named as EP/3D) _c -SiC ₁₅ -APTES)；。

In the step S1, bisphenol A type epoxy resin is adopted as the epoxy resin, methyl hexahydrophthalic anhydride is adopted as the curing agent, and 2-ethyl-4-methylimidazole is adopted as the accelerator; the epoxy resin, the curing agent, the accelerator and the 3D _c -SiC ₁₅ The dosage of APTES is 100g, 90g, 0.6g, 21g, respectively; the stirring time is 30-60 minutes.

In step S1, the continuous degassing time is 6-12 hours.

In step S1, the step heating curing temperature and time are respectively: at 90-100 deg.C for 1-2 hr, at 110-120 deg.C for 2-4 hr, and at 130-135 deg.C for 1-2 hr.

The epoxy resin prepared by the methodComposite material (EP/3D) _c -SiC ₁₅ APTES) as shown in FIG. 7. Due to the successful grafting of the silane coupling agent APTES, the aerogel framework loaded with the SiC-APTES has good interface compatibility with an epoxy resin matrix. In addition, full 3D _c -SiC ₁₅ The APTES skeleton is not damaged, which ensures EP/3D _c -SiC ₁₅ -effective conductive paths in APTES composites.

EP/3D prepared in this example _c -SiC ₁₅ The volume fraction of modified silicon carbide (SiC-APTES) in APTES is 7.1%, and the volume fraction is calculated by the true density.

Example 2

The preparation method of the pure cellulose aerogel in the embodiment comprises the following specific steps:

6g of cellulose powder, 7g of NaOH solid particles, 12g of urea and 71g of deionized water are mixed, and the mixture is mechanically stirred for 1 hour at the low temperature of-12 ℃; placing the mixture in a high-speed centrifuge with the speed of 1000-1500r/min for centrifugal degassing for 10-15 minutes, then transferring the mixture into a sealed mould and placing the sealed mould in a thermostat for heating and crosslinking for 6 hours at the temperature of 60 ℃; repeatedly washing with deionized water for several times after crosslinking is finished to obtain pure cellulose hydrogel; finally, the hydrogel is frozen and dried for 48 to 72 hours at the temperature of-50 ℃ and the pressure of 0.0001Pa to obtain the pure cellulose aerogel.

The scanning electron microscope image of the prepared pure cellulose aerogel is shown in fig. 6, and as shown in fig. 6, the cellulose aerogel framework presents a uniform 3D porous structure, so the SiC-APTES filler can be regularly embedded in the aerogel framework.

The preparation method of the epoxy resin composite material in the embodiment is as follows:

and S2, soaking the prepared pure cellulose aerogel into epoxy resin until the pure cellulose aerogel is completely permeated. Then transferring the mixture into a vacuum drying oven, and continuously vacuumizing at room temperature;

s3, placing the impregnated epoxy composite material in a stainless steel mold for carrying outHeating up and curing in a step way to form the epoxy resin composite material (named as EP/3D) _c )。

In the step S1, bisphenol A type epoxy resin is adopted as the epoxy resin, methyl hexahydrophthalic anhydride is adopted as the curing agent, and 2-ethyl-4-methylimidazole is adopted as the accelerator; the dosage of the epoxy resin, the curing agent and the accelerator is 100g, 90g and 0.6g respectively; the stirring time is 30-60 minutes.

In step S1, the continuous degassing time is 6-12 hours.

The epoxy resin composite (EP/3D) prepared as described above _c ) FIG. 8 shows a scanning electron micrograph of (A). In EP/3D _c In the method, the pores of the cellulose aerogel are completely filled by the epoxy resin matrix, the cross section of the cellulose aerogel is flat and smooth, and no obvious interface defect exists between the aerogel framework and the resin matrix.

Example 3

The difference between this example and example 1 is that, in the preparation method of the modified silicon carbide supported cellulose aerogel in this example, in step 1), the amounts of the SiC-APTES particles, the cellulose powder, the NaOH solid particles, and the urea are 3g, 6g, 7g, and 12g. The epoxy resin composite material prepared in this example is named EP/3D _c -SiC ₃ APTES, EP/3D prepared in this example _c -SiC ₃ The volume fraction of modified silicon carbide (SiC-APTES) in APTES was 1.54%.

Example 4

The present embodiment is different from the comparative document 1 in that, in the method for preparing the modified silicon carbide supported cellulose aerogel in the present embodiment, in the step 1), the amounts of the SiC-APTES particles, the cellulose powder, the NaOH solid particles, and the urea are 6g, 7g, and 12g. The epoxy resin composite material prepared in this example is named EP/3D _c -SiC ₆ APTES, EP/3D prepared in this example _c -SiC ₆ The volume fraction of modified silicon carbide (SiC-APTES) in APTES was 3.23%.

Example 5

The difference between this example and example 1 is that, in the preparation method of the modified silicon carbide supported cellulose aerogel in this example, in step 1), the amounts of the SiC-APTES particles, the cellulose powder, the NaOH solid particles, and the urea were 9g, 6g, 7g, and 12g. The epoxy resin composite material prepared in this example is named EP/3D _c -SiC ₉ APTES, EP/3D prepared in this example _c -SiC ₉ The volume fraction of modified silicon carbide (SiC-APTES) in APTES was 4.47%.

Example 6

The difference between this example and example 1 is that, in the preparation method of the modified silicon carbide supported cellulose aerogel in this example, in step 1), the amounts of the SiC-APTES particles, the cellulose powder, the NaOH solid particles, and the urea are 21g, 6g, 7g, and 12g. The epoxy resin composite material prepared in this example is named EP/3D _c -SiC ₂₁ APTES, EP/3D prepared in this example _c -SiC ₂₁ The volume fraction of modified silicon carbide (SiC-APTES) in APTES was 10.58%.

Example 7

(2) Then, carrying out suction filtration on the solution through a Buchner funnel to obtain hydroxylated SiC (named SiC-OH), alternately washing the solution for 3 times by using absolute ethyl alcohol and deionized water, and then placing the washed solution in an oven for heating and drying to obtain SiC-OH particles;

(4) And finally, carrying out suction filtration on the solution through a Buchner funnel, washing the solution for multiple times by using deionized water, and carrying out vacuum freeze drying to obtain APTES modified SiC particles, namely the modified silicon carbide (named as SiC-APTES).

In the step (1), the mass of SiC particles is 2g, the particle size is 5 microns, the volume of NaOH solution is 200mL, the concentration is 1mol/L, the ultrasonic treatment time is 30 minutes, the constant-temperature magnetic stirring temperature is 80 ℃, and the stirring reaction time is 24 hours.

In the step (4), the freeze-drying temperature is-50 ℃, the pressure is 0.0001Pa, and the drying time is 24 hours.

and S2, immersing the prepared SiC-APTES framework into epoxy resin until the SiC-APTES framework is completely permeated. Then transferring the mixture into a vacuum drying oven, and continuously vacuumizing at room temperature;

and S3, placing the impregnated epoxy composite material in a stainless steel mold, and carrying out stepped heating, curing and molding to obtain the epoxy resin composite material (named as EP/SiC-APTES).

In the step S1, bisphenol A epoxy resin is adopted as the epoxy resin, methyl hexahydrophthalic anhydride is adopted as the curing agent, and 2-ethyl-4-methylimidazole is adopted as the accelerator; the dosage of the epoxy resin, the curing agent, the accelerator and the SiC-APTES are respectively 100g, 90g, 0.6g and 8.3g; the stirring time is 30-60 minutes.

In step S1, the continuous degassing time is 6-12 hours.

The volume fraction of modified silicon carbide (SiC-APTES) in the EP/SiC-APTES prepared in this example was 1.54%.

Example 8

The difference between this example and example 7 is that the amount of SiC-APTES used in this example is 17.7g, and the volume fraction of modified silicon carbide (SiC-APTES) in EP/SiC-APTES prepared in this example is 3.23%.

Example 9

This example differs from example 7 in that the amount of SiC-APTES used in this example was 24.8g, and the volume fraction of modified silicon carbide (SiC-APTES) in the EP/SiC-APTES prepared in this example was 4.47%.

Example 10

The difference between this example and example 7 is that the amount of SiC-APTES used in this example was 40.4g, and the volume fraction of modified silicon carbide (SiC-APTES) in EP/SiC-APTES prepared in this example was 7.1%.

Example 11

The difference between this example and example 7 is that the amount of SiC-APTES used in this example was 62.6g, and the volume fraction of modified silicon carbide (SiC-APTES) in EP/SiC-APTES prepared in this example was 10.58%.

Example 12

This example differs from example 7 in that the amount of SiC-APTES used in this example was 132.3g, and the volume fraction of modified silicon carbide (SiC-APTES) in the EP/SiC-APTES prepared in this example was 20%.

Example 13

This example differs from example 7 in that the amount of SiC-APTES used in this example was 226.7g, and the volume fraction of modified silicon carbide (SiC-APTES) in the EP/SiC-APTES prepared in this example was 30%.

Switch field threshold E for epoxy composites and neat epoxy prepared in examples 11-13 _c And non-linearity index beta As shown in FIG. 9, switching field threshold E of epoxy resin composites prepared in examples 1-6 _c And the non-linearity index β is shown in fig. 10.

As can be seen from FIGS. 9-10, there is a percolation threshold in the epoxy composite, which is determined by the amount of SiC-APTES present. As the filling amount of the SiC-APTES is increased, when the filling amount reaches a percolation threshold value, the epoxy resin composite material presents obvious nonlinear conductive characteristics. FIG. 9 shows that when SiC-APTES is used as the materialWhen the integral fraction reaches 20%, the EP/SiC-APTES composite material begins to have nonlinear conductivity, the pressure-sensitive field intensity is 3.35kV/mm, and the nonlinear index is 5.65. However, as can be seen from FIG. 10, 3D compares to EP/SiC-APTES composites _c the-SiC-APTES interconnection structure enables EP/3D _c The percolation threshold of the SiC-APTES composite is significantly reduced (about 78%). EP/3D with very low SiC-APTES content (4.47 vol%) _c -SiC ₉ The APTES composite material has obvious field conductance nonlinear characteristic, the pressure-sensitive field strength is 5.09kV/mm, and the nonlinear coefficient is 2.17. Furthermore, starting from 4.47vol%, EP/3D as the loading increases _c The nonlinear coefficient of the SiC-APTES composite material is increased, and the pressure-sensitive field intensity is gradually reduced. EP/3D when the volume fraction reaches 10.58vol% _c -SiC ₂₁ The APTES composite material shows excellent nonlinear electrical conductivity, the pressure-sensitive field strength of the APTES composite material is 2.49kV/mm, and the nonlinear coefficient of the APTES composite material is 4.54. In contrast, EP/SiC of the same volume fraction ₂₁ APTES composites remain a linear material without nonlinear electrical conductivity characteristics.

Pure epoxy resin (EP) and examples 7-11 EP/SiC-APTES with different volume fractions of SiC-APTE As shown in FIG. 11, examples 1-6 EP/3D with different volume fractions of SiC-APTE _c The thermal conductivity of the-SiC-APTES composite is shown in FIG. 11, in which the thermal conductivity of the EP/SiC-SPTES composite having randomly distributed SiC is 0.19W/mK, 0.22W/mK, 0.26W/mK, 0.3W/mK and 0.35W/mK at 1.54vol%, 3.23vol%, 4.47vol%, 7.1vol% and 10.58vol%, respectively, and EP/3D after self-assembling SiC on a cellulose aerogel skeleton _c The thermal conductivity of the-SiC-SPTES composite material at 1.54vol%, 3.23vol%, 4.47vol%, 7.1vol% and 10.58vol% is 0.21W/mK, 0.24W/mK, 0.3W/mK, 0.45W/mK and 0.69W/mK respectively. The thermal conductivity of both types of epoxy composites increases with the volume fraction of filler, which can be attributed to the higher intrinsic thermal conductivity of SiC. Meanwhile, the silane coupling agent grafted on the surface of the silicon carbide can enhance the interface bonding force, form covalent connection with an epoxy group, improve the interface compatibility of the silicon carbide and an epoxy resin matrix, remarkably reduce the interface phonon scattering effect and the interface thermal resistance, and improve the heat conduction systemAnd (4) counting. Furthermore, pure epoxy resins and EP/3D _c Thermal conductivity of the composite material is only 0.18-0.19W/mK, and 10.58vol% EP/3D _c -SiC ₂₁ The thermal conductivity of APTES is as high as 0.69W/mK, which is improved by about 300% compared with pure epoxy resin and is higher than that of EP/SiC of SiC-APTES with random distribution ₂₁ The thermal conductivity (0.35W/mK) of the APTES composite material is higher than 100%, and at the same volume fraction, EP/3D _c The thermal conductivity of the-SiC-APTES is higher than that of the EP/SiC-APTES, and the EP/3D _c The larger the volume fraction of SiC-APTES in the-SiC-APTES composite material is, the more remarkable the increase of the thermal conductivity coefficient is. When the volume fraction is less than 4.47vol%, the thermal conductivity increases linearly to a small extent, indicating that there is no thermal conduction path. Starting from 4.47vol%, the slope increases significantly as the SiC-APTES loading increases. The method shows that the cellulose framework provides a 3D interconnection network, and the SiC-APTES loaded on the 3D framework aims at constructing a high-efficiency heat conduction path, reducing heat loss generated by interface thermal resistance and shortening a heat conduction path, so that the method has the advantage of remarkably improving the heat conductivity coefficient.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.

Claims

1. The epoxy resin composite material is characterized by comprising the following components in parts by mass: 15-50 parts of modified silicon carbide-loaded cellulose aerogel, 80-120 parts of epoxy resin, 80-110 parts of curing agent and 0.5-2 parts of accelerator; the modified silicon carbide in the cellulose aerogel loaded with the modified silicon carbide is coupling agent modified silicon carbide.

2. The epoxy resin composite according to claim 1, wherein the modified silicon carbide in the modified silicon carbide-loaded cellulose aerogel is 1 to 30% by mass of the epoxy resin composite.

3. The epoxy resin composite material according to claim 1 or 2, wherein the preparation method of the modified silicon carbide-loaded cellulose aerogel comprises the following steps:

(1) Dispersing modified silicon carbide in water, adding cellulose, naOH and urea, mixing, and stirring the mixture;

(2) Degassing the mixture after stirring, and heating for crosslinking;

(3) And after crosslinking is finished, obtaining the cellulose hydrogel loaded with the modified silicon carbide, and drying to obtain the cellulose aerogel loaded with the modified silicon carbide.

4. The epoxy resin composite material according to claim 3, wherein in the step (1), the mass ratio of the modified silicon carbide to the cellulose is 1: (2-5).

5. The epoxy resin composite material according to claim 3, wherein in the step (1), the preparation method of the modified silicon carbide comprises the following steps:

6. The epoxy resin composite material according to claim 5, wherein in the step (2), the mass ratio of the hydroxylated SiC to the coupling agent is (2-5): 1.

7. a method for preparing the epoxy resin composite material according to any one of claims 1 to 6, comprising the steps of:

8. The preparation method of the epoxy resin composite material according to claim 7, wherein in the step (2), the gradient temperature rise curing specifically comprises the following steps: curing at 90-100 deg.C for 1-2 hr, curing at 110-120 deg.C for 2-4 hr, and curing at 130-135 deg.C for 1-2 hr.

9. Use of the epoxy resin composite material according to any one of claims 1 to 6 in an electric field gradient material.