CN114891255B - Glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin and preparation method and application thereof - Google Patents

Abstract

The invention discloses a glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin, a preparation method and application thereof. The preparation method comprises the steps of blending and freeze-drying a stripped h-BN nanosheet sample and a glass fiber sample grafted by surface epoxy, obtaining a eGF & BNNS three-dimensional ordered frame, immersing the frame in an uncured epoxy resin mixed solution, utilizing vacuum auxiliary immersion and step curing, and cleaning to obtain the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin. The arc resistance and the mechanical strength of the epoxy resin composite insulating medium have more remarkable synergistic enhancement effect, and the dosage of BNNS and eGF and the comprehensive performance of the composite material show good positive correlation, so that the contradiction that the arc resistance and the mechanical strength of the medium cannot be considered is effectively solved.

Description

A glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin and Preparation method and application

technical field

The invention belongs to the technical field of insulating material preparation, and in particular relates to a novel insulating material, a preparation method and an application thereof.

Background technique

Limited by its own thermal conductivity, the epoxy resin insulating medium will suffer severe thermal damage under the local high temperature of the arc, which restricts its application in extreme conditions such as the fracture of high-voltage DC circuit breakers. Metal particles, carbon-based High thermal conductivity fillers such as materials and inorganic ceramic materials can improve the arc resistance of the medium by timely evacuating the local high temperature on the surface of the EP insulation medium under the action of arc thermal stress. Among the many types of high thermal conductivity particles, the two-dimensional structure of hexagonal boron nitride (h-BN for short) is currently known as one of the reinforcing fillers with the best combination of thermal conductivity and insulation performance. However, the accumulation of lamellar crystals in the height direction at a higher h-BN filling concentration will greatly reduce the side area of the filler, which not only affects the dispersion effect of h-BN nanosheets in the EP matrix and the performance of thermal conductivity, but also cannot To avoid the uneven distribution of the internal stress of the composite EP medium under the action of external force, thereby reducing the inherent mechanical strength of EP. This contradiction between thermal conductivity and mechanical strength is the main bottleneck restricting the application of h-BN filled composite EP in the fracture insulation of HVDC circuit breakers.

Contents of the invention

In order to solve the problems existing in the prior art, the method of the present invention adopts the directional regulation and control process of the ice crystal-induced filler, and prepares the epoxy resin composite insulation medium impregnated with the glass fiber reinforced h-BN three-dimensional ordered framework grafted by epoxy groups, And it effectively solves the contradiction between the thermal and mechanical properties of the medium, and realizes the substantial synergistic improvement of the arc resistance performance and mechanical strength of the medium.

A preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin, said method comprising the following steps:

s1. Stripping of hexagonal boron nitride: add hexagonal boron nitride (marked as h-BN) into an organic solvent for ultrasonic dispersion treatment for 35-50 hours. The clear liquid is suction-filtered, and the precipitate obtained by the suction filtration is dried to obtain the stripped h-BN nanosheet sample which is BNNS;

In some preferred technical solutions, the organic solvent described in s1 includes but is not limited to DMF.

In some more preferred technical solutions, the specific technical solutions of s1 are as follows:

s1-1. Take a certain amount of dried h-BN and add it to the DMF solution to make a suspension with a concentration of 10mg/mL, and continue ultrasonic treatment for 48h at a power of 300W.

s1-2. After the dispersion obtained in s1-1 was left to stand for 12 hours, the upper suspension was taken and centrifuged at 1000 rpm for 10 minutes. Afterwards, the supernatant was collected and further centrifuged at 4000 rpm for 30 min.

s1-3. Suction filter the supernatant obtained in s1-2, and dry the bottom sediment at 60° C. for 12 hours.

s2, surface chemical grafting of glass fibers: glass fibers (marked as GF) are added to the piranha etching solution, fully stirred, washed to neutral and dried to obtain treated glass fibers; the treated glass fibers Add it to the mixed solution of NaOH solution and epichlorohydrin EPI and stir well; then wash and dry in sequence to obtain the surface epoxy-grafted glass fiber sample eGF;

The piranha etching solution described in s2 is a mixture of 98% concentrated hydrochloric acid and 30% hydrogen peroxide with a volume ratio (6-9): 3;

In some specific technical solutions: in s2, the specific operations are as follows:

s2-1. Add a certain amount of glass fiber into the piranha etching solution made of 98% concentrated hydrochloric acid and 30% hydrogen peroxide in a volume ratio of 7:3, and stir magnetically at 95°C for 1 hour.

s2-2. Take the stirred solution in s2-1, wash it repeatedly with deionized water until neutral, and dry it in an oven at 40°C for 24 hours.

s2-3. Add the GF-OH in s2-2 to the mixed solution of 10mL NaOH (1.5mol/L) and 5mL EPI, stir magnetically at 25°C for 12h, and filter the obtained product with water and wash it in Dry at 40°C for 48 hours to obtain eGF. s3. The glass fiber samples of the stripped h-BN nanosheets and surface epoxy grafted: BNNS and sodium carboxymethyl cellulose SCMC were mixed with water to obtain a BNNS/SCMC suspension; the eGF was evenly dispersed in water to obtain eGF suspension;

Wherein: the BNNS concentration in the BNNS/SCMC suspension is 1-20wt%, and the SCMC concentration is 0.1-5wt%;

s4. Preparation of eGF&BNNS three-dimensional ordered framework: blend the BNNS/SCMC suspension in s3 with the eGF suspension, stir at 70-90°C for 4-6 hours, pour it into a mold, and place it in liquid nitrogen Directional freezing; finally, the frozen sample is transferred to a freeze dryer for freeze-drying to obtain a dried three-dimensional ordered framework of eGF&BNNS;

Among them: the freeze-drying condition is that the temperature is -100~-50°C, the pressure is ≤0.5Pa, and the freeze-drying time is 24~72h; the mass ratio of eGF to BNNS is 0.5~5:1;

s5. Preparation of eGF&BNNS three-dimensional ordered framework impregnated with epoxy resin: use matrix, curing agent and accelerator to prepare mixed solution, immerse the eGF&BNNS three-dimensional ordered framework prepared in s4 into the evenly stirred mixed solution; After fully impregnated under pressure and vacuum, the compound was solidified by gradient temperature rise to obtain the epoxy resin sample EP composed of eGF&BNNS three-dimensional ordered framework.

In s5, the specific operation is as follows:

s5-1. Preheat a certain amount of DGEBA resin at 60°C for 10 minutes, then add curing agent and accelerator in sequence; stir the formed mixture at 70°C for 30 minutes, and then fully degas it.

s5-2. Immerse the prepared eGF&BNNS three-dimensional ordered framework into the evenly stirred DGEBA/MTHPA/DMP-30 mixture; first pre-impregnate at 60°C for 2 hours under normal pressure, then transfer to a vacuum drying oven, and further Vacuum assisted impregnation at 60 °C for 4 h.

s5-3. The fully impregnated composite is cured by gradient temperature (90°C for 2 hours, 110°C for 2 hours). After the curing reaction is completed, the obtained sample is naturally cooled to room temperature, and then removed from the mold and treated with absolute ethanol. After cleaning, the EP sample composed of eGF&BNNS three-dimensional ordered framework is obtained.

In the technical solution of the present invention, in s2, the condition for sufficient stirring is to stir at a temperature of 90-100° C. for 0.5-1.5 h; preferably: in s2, the concentration of NaOH solution is 1-3 mol/L; the treated GF , The mass volume ratio between NaOH solution and epichlorohydrin EPI is 50-60g: 5-15mL: 3-8mL;

In the technical solution of the present invention: in s3, the BNNS concentration in the BNNS/SCMC suspension is 3-15 wt%, the SCMC concentration is 0.1-2 wt%, and the eGF concentration in the eGF suspension is 15-30 wt%.

In the technical solution of the present invention: in s4, the freeze-drying conditions are that the temperature is -90--70°C, the pressure is less than 0.1-0.5Pa, and the freeze-drying time is 40-50 hours; the mass ratio of eGF to BNNS is 0.5-2: 1.

In the technical scheme of the present invention: in s5, DGEBA epoxy resin is used as matrix, methyltetrahydrophthalic anhydride (MTHPA) is used as curing agent, and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) is used as accelerator agent.

In the technical solution of the present invention: in s5, the mass ratio of the matrix, the curing agent and the accelerator is 100:70-90:1-5.

In the technical solution of the present invention: in s5, the curing conditions are 1-3 hours at 85-95°C, and 1-3 hours at 100-120°C.

In the technical solution of the present invention: in s5, the mass ratio of the eGF&BNNS three-dimensional ordered framework to the mixed solution is 0.1-0.3:1.

A glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin, the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin is prepared by the above preparation method.

In the technical solution of the present invention, the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin prepared by the above method is used in the field of electrical insulation.

In the technology of the present invention, the application of the aforementioned preparation method in improving the arc resistance performance of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin is provided. The arc resistance performance is reflected in the _SF6 atmosphere. After the prepared EP composite dielectric sample was subjected to an arc damage test, the DC surface flashover voltage of the damaged sample was obtained.

In s3, in order to enhance the mechanical stability of the nanosheet framework, a certain concentration of adhesive SCMC needs to be added; preferably, when the SCMC mass concentration and its influence are:

Further, after the h-BN sheet described in s1 is subjected to DMF ultrasonic stripping treatment, the prepared BNNS is flat and single-sheet dispersed on the mica sheet substrate, and the thickness of a single sheet crystal is only 5nm, and the corresponding radial dimension decreases As small as 150-200nm. It can be seen from the morphology under the transmission electron microscope that the exfoliated BNNS has a uniform thickness and a clear edge structure.

Furthermore, the eGF described in s2 has a relatively obvious characteristic absorption peak of epoxy group at 910 cm ⁻¹ in its Fourier transform infrared spectrometer (FTIR) spectral line. The grafting of epoxy groups led to the appearance of two new absorption peaks in the FTIR spectrum of eGF, respectively representing the Si-O-Si structure (1050cm ^-1 ) and Si-C structure (840cm ^-1 ) in organosilicon; Furthermore, the X-ray photoelectron spectrometer (XPS-O1s) narrow-spectrum scanning results showed that the oxygen atoms on the surface of the prepared eGF samples produced two new types of CO-Si bonds at 532.4eV and COC bonds at 531.6eV. the bonding method

The fourth object of the present invention is to provide the application of the aforementioned preparation method in improving the mechanical strength of glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework composite epoxy resin.

The fifth object of the present invention is to provide the application of the aforementioned preparation method in synergistically improving the arc resistance and mechanical properties of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin medium.

The beneficial effects of the present invention are:

1) Studies have shown that the synthesized glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework (3D-eGF&BNNS) compared with the unglass fiber reinforced hexagonal boron nitride three-dimensional ordered framework (3D-BNNS), the internal average pore diameter and the total The pore volume decreased by 66.2% and 50.1%, the total pore area increased by 47%, the bulk density and apparent density increased by 93.6% and 35.1%, respectively, and the mechanical properties of the frame itself were significantly improved.

2) The composite epoxy resin of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework obtained by the present invention has a higher surface flashover voltage. Compared with pure EP, the BNNS with a mass concentration of 11wt.% The surface flashover voltage of the composite EP medium increased by 15.0% compared with the pure EP medium after the sequence frame was impregnated. However, after arc damage, the electrical resistance along the surface of the 3D-BNNS/EP composite dielectric increases significantly with the increase of BNNS concentration, and the introduction of epoxy-grafted glass fibers into the BNNS three-dimensional ordered framework does not damage the 3D-BNNS/EP composite dielectric. BNNS/EP composite medium has intrinsic electrical resistance along the surface and excellent arc resistance performance. Among them, when the mass fraction of BNNS is 11wt.%, eGF/BNNS=1:1, the arc resistance performance of the composite EP medium is increased compared with that of pure EP. 3.46 times larger.

3) The composite epoxy resin of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework constructed by the present invention can improve the degree of arc damage. Compared with pure EP, the arc damage degree of 3D-eGF&BNNS/EP composite medium has been significantly improved. The severe carbonization on the surface of the medium transformed into relatively uniform local slight damage, and the carbonization area decreased by 86.5% compared with that of pure EP, and the surface of the composite medium showed a clear long-range ordered structure after arcing, which was consistent with the BNNS three-dimensional ordered frame shape. The appearance is similar, indicating that the prepared three-dimensional framework can still be relatively intact in the EP matrix even under the local high temperature of the arc, thereby effectively inhibiting the melting and decomposition of the matrix.

4) The composite epoxy resin of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework constructed by the present invention significantly improves the mechanical strength and ductility of the medium. Compared with pure EP, epoxy resin is introduced into the three-dimensional ordered framework of BNNS The mechanical properties of the 3D-eGF&BNNS/EP composite medium were significantly improved after the group-grafted eGF, and the mechanical strength and ductility of the 3D-eGF&BNNS/EP composite medium were superior to those of the pure EP medium when the mass ratio of eGF/BNNS was only 0.5:1. When the mass ratio of eGF/BNNS was increased to 1:1, the tensile strength of 3D-eGF&BNNS/EP composite media reached 97.04 MPa, which was 85.5% higher than that of pure EP media.

Description of drawings

Fig.1 SEM images of three-dimensional ordered frameworks with different BNNS concentrations. (a) 3DBNNS#2; (b) 3DBNNS#3; (c) 3DBNNS#4; (d) 3DBNNS#1

Figure 2 Macroscopic and microscopic morphologies of 3D BNNS#1 and eGF&3DBNNS#1 three-dimensional ordered framework. (a), (g) 3D BNNS physical image; (b), (h) eGF&3DBNNS#1 physical image; (c), ( d) The internal three-dimensional structure of 3DBNNS#1 and eGF&3DBNNS#1; (e), (f) SEM morphology of the cross-section of 3DBNNS#1 and eGF&3DBNNS#1S

Fig.3 SEM morphology of eGF&BNNS three-dimensional ordered framework with different mass ratios (a) eGF&3DBNNS#2; (b) eGF&3DBNNS#1; (c) eGF&3DBNNS#3

Figure 4 Internal pore size distribution and physical parameters of 3DBNNS#1 and eGF&3DBNNS#1 three-dimensional ordered framework

Fig.5 Surface morphology of different EP composite media with the same BNNS concentration after arc damage (a) EP#0; (b) EP#4; (c) EP#1

Fig.6 DC surface flashover voltages of different EP composite insulating media after arc damage (a) EP with different BNNS mass concentrations; (b) EP with different eGF/BNNS mass ratios

Figure 7. Thermal infrared images and surface temperature change trends of different EP insulation media (a) physical map; (b) heating process; (c) heating curve; (d) cooling curve after arc action; (e) cooling after arc action process

Fig. 8 Stress-strain curves and tensile strength of different EP composite media.

Detailed ways

The present invention will be further described below in conjunction with embodiment, but protection scope of the present invention is not limited to this:

The source and the purity of the used chemical reagents in the method sample preparation of the present invention are shown in Table 1:

Table 1 List of main experimental raw materials

The model and the source of the main experimental instrument of the method sample preparation of the present invention are shown in Table 2:

Table 2 List of main experimental instruments for sample preparation

The present invention will be further described through specific examples below, so that those skilled in the art can better understand the present invention and implement it, but the given examples are not intended to limit the present invention.

Example 1

s1. Stripping of hexagonal boron nitride: Take 10g of dried hexagonal boron nitride (h-BN) and add it to 1LDMF solution to make a suspension with a concentration of 10mg/mL, and continue ultrasonic treatment for 48h at a power of 300W; After the obtained dispersion was allowed to stand for 12 h, the upper suspension was taken and centrifuged at 1000 rpm for 10 min. Afterwards, the supernatant was collected and further centrifuged at 4000 rpm for 30 min; and subjected to suction filtration, and the bottom precipitate was dried at 60° C. for 12 h. That is, the exfoliated h-BN nanosheet sample (marked as BNNS) was obtained.

s2. Surface chemical grafting of glass fibers: Add 55g of glass fibers into the piranha etching solution made of 140mL 98% concentrated hydrochloric acid and 60mL30% hydrogen peroxide, fully stir (stir at 95°C for 1h), and then use deionized Wash with water repeatedly until neutral, and dry in an oven at 40°C for 24 hours. The treated GF was added to a mixed solution of 10mL NaOH solution (1.5mol/L) and 5mL EPI, magnetically stirred at 25°C for 12h, and the resulting product was suction filtered and washed with water, then dried at 40°C for 48h, A surface epoxy grafted glass fiber sample (marked as eGF) was obtained.

s3. Pretreatment of BNNS: Take 500ml of deionized water, add 6gSCMC and 63gBNNS in sequence, that is, the concentration of BNNS in the prepared aqueous solution is 11wt.%, and the concentration of SCMC is 1wt.%. Ball milling at 300rpm for 2h; take 180mL of deionized Water, add 63g of eGF prepared in s2, that is, the concentration of eGF in the prepared aqueous solution is 26wt.%, and ultrasonically disperse in deionized water with a power of 360W for 30min.

All the above-treated BNNS/SCMC suspensions were blended with eGF suspensions, that is, the mass ratio of eGF to BNNS was 1:1, and magnetically stirred at 80°C for 5 hours to obtain a uniform water-based eGF&BNNS slurry.

s4. Preparation of BNNS three-dimensional ordered framework: the suspension treated in s3 was magnetically stirred at 80°C for 5 hours, then poured into a mold, and placed in liquid nitrogen for directional freezing; finally, the frozen sample Transfer to a freeze dryer and freeze-dry at -80°C/0.5Pa for 48 hours to obtain the dried eGF&BNNS three-dimensional ordered framework; labeled as eGF&3DBNNS (#1).

Example 2

In the embodiment, except for s3, 31.5g eGF was taken, that is, the mass ratio of eGF and BNNS was 0.5:1, and the rest were the same as in Example 1, and the three-dimensional ordered framework of eGF&BNNS was made and marked as eGF&3DBNNS (#2).

Example 3

In the embodiment, except for s3, 126g eGF was taken, that is, the mass ratio of eGF and BNNS was 2:1, and the rest were the same as in Example 1, and the three-dimensional ordered framework of eGF&BNNS was made and marked as eGF&3DBNNS (#3).

Example 4

In this embodiment, the s2 operation is not performed, and the eGF suspension is not mixed into the BNNS/SCMC suspension in s3, and the rest are the same as in Example 1, and the three-dimensional ordered frame of BNNS is marked as 3DBNNS (#1 ).

Example 5

In this embodiment, except for s3, 15.5gBNNS and 5.2gSCMC are taken, and the mass concentration of BNNS in the aqueous solution is 3wt.%. ).

Example 6

In this example, except for s3, 38gBNNS and 5.4gSCMC are taken, that is, the mass concentration of BNNS in the aqueous solution is 7wt.%. .

Example 7

In this example, except for s3, 50gBNNS and 5.6gSCMC are taken, that is, the mass concentration of BNNS in the aqueous solution is 9wt.%. .

Example 8

This example examines the influence of the mass concentration of BNNS in the BNNS pretreatment step on the fabricated three-dimensional ordered framework.

Table 4 reactant concentration screening variable table

group Concentration of BNNS sample name Example 4 11wt.% 3DBNNS (#1) Example 5 3wt.% 3DBNNS (#2) Example 6 7wt.% 3DBNNS (#3) Example 7 9wt.% 3DBNNS (#4)

The cross-sectional SEM morphology of each frame sample is shown in Fig. 1.

The three-dimensional ordered frameworks with different BNNS concentrations have similar long-range ordered structures microscopically, and the differences between samples are mainly reflected in the tightness of BNNS arrangement in each layer of the framework and the spacing between adjacent layers. With the increase of BNNS concentration, the spacing decreases to some extent, but the overall distribution is on the order of tens of μm.

The above experimental results show that the screened BNNS concentration is 1-15wt.%, wherein, when the BNNS concentration is 11wt.%, the three-dimensional ordered framework of the prepared BNNS is arranged most closely.

Example 9

This example examines the influence of the mass ratio of eGF/BNNS on the fabricated three-dimensional ordered framework.

Table 5 Reactant ratio screening variable table

group eGF:BNNS product name Example 1 1:1 eGF&3DBNNS(#1) Example 2 0.5:1 eGF&3DBNNS (#2) Example 3 2:1 eGF&3DBNNS (#3) Example 4 0:1 3DBNNS (#1)

(1) SEM morphology of 3DBNNS and eGF&3DBNNS

Figure 2 shows the macroscopic and microscopic morphologies of 3DBNNS (#1) and eGF&3DBNNS (#1).

From the macroscopic physical map and the internal 3D topography map, it can be seen that the introduction of eGF has no significant effect on the long-range ordered wall-like hierarchical structure in the BNNS 3D ordered framework. The rod-shaped eGF is evenly attached to the three-dimensional ordered framework under the bonding effect of fibrous SCMC molecules, interspersed between adjacent BNNS layers, resulting in a slight increase in the spacing between adjacent layers in the frame from ~25 μm to ~ 50 μm.

After the introduction of eGF grafted with epoxy groups, the mechanical strength of the BNNS three-dimensional ordered framework has been greatly improved. The sample eGF&3DBNNS (#1) can still maintain a fairly stable structure under the load of 500g weight, which is higher than that of 3DBNNS ( #1) has nearly 5 times higher load strength.

Figure 3 shows the SEM morphology of eGF&3DBNNS(#1), eGF&3DBNNS(#2) and eGF&3DBNNS(#3).

It can be seen that as the mass ratio of eGF/BNNS increases, that is, the amount of eGF increases, the space between BNNS levels in the three-dimensional ordered frame will be gradually filled by eGF and connected to each other, resulting in the gap between adjacent levels further increase.

(2) Analysis of internal pore size distribution and physical parameters of eGF&3DBNNS

The internal pore size distribution and physical parameters of BNNS (#1) and eGF&3DBNNS (#1) were tested and analyzed by mercury porosimetry, and the results are shown in Figure 4.

The analysis showed that compared with 3DBNNS (#1), the internal average pore diameter and total pore volume of eGF & 3DBNNS (#1) decreased by 66.2% and 50.1%, respectively. Combining the physical parameters of the sample in Fig. 4(a) with the curve of "mercury injection differential-pore diameter" in Fig. 4(b), it can be seen that after enhanced by eGF, the length of the large-aperture pores in the three-dimensional ordered frame decreases, while The length of the small-aperture pores increased, resulting in a 47% increase in the total pore area of the eGF&BNNS three-dimensional ordered framework, and a 93.6% and 35.1% increase in the bulk density and apparent density, respectively.

Example 10

s1: DGEBA resin was preheated at 60°C for 10 minutes, and then the preheated DGEBA epoxy resin, methyltetrahydrophthalic anhydride (MTHPA), 2,4,6-tri(di Methylaminomethyl)phenol (DMP-30) was mixed and stirred at 70°C for 30min, and then fully degassed to obtain a mixed solution.

s2: Immerse the mass ratio of 0.2:1eGF&3DBNNS (#1) (prepared in Example 1) into the mixture; first pre-impregnate at 60°C under normal pressure for 2h, then transfer to a vacuum drying oven, and further dry at 60°C Vacuum assisted impregnation for 4h.

s3: The fully impregnated composite is cured by gradient temperature (90°C for 2 hours, 110°C for 2 hours). After the curing reaction is completed, the obtained sample is naturally cooled to room temperature, and then removed from the mold and cleaned with absolute ethanol. That is, the EP sample composited with eGF&BNNS three-dimensional ordered framework is obtained, which is denoted as EP#1.

Example 11

In this example, except for s2, the three-dimensional ordered framework is not impregnated in the mixed liquid, and the rest are the same as in Example 10 to make a pure epoxy resin, which is marked as EP#0.

Example 12

In this example, except for s2, the three-dimensional ordered frameworks produced in Examples 2-7 are sequentially immersed in the mixed solution, and the others are the same as Example 10, which are respectively marked as EP#2-EP#7.

Embodiment 13 The arc resistance performance of 3D-eGF&BNNS/EP

(1) Arc damage test

In the SF ₆ atmosphere, different energy arcs were used to controlly damage the samples prepared in Examples 10-12, and the average gray value of the damaged area on the surface of the EP#0 sample was used as the threshold value, and the gray value in each picture was extracted. The pixel points with a value of , are regarded as the carbonized area, and the corresponding carbonized area S _c can be obtained by calculating the proportion of the carbonized area pixel points in each picture, as shown in Figure 5.

After EP#0 was subjected to local high-temperature arcing, most of the area between the surface electrodes was severely carbonized due to its own arc resistance, and the carbonization area reached 17.48mm ² (Fig. 5(a)). At this time, the dielectric matrix will be fully melted after the arc action, producing a large number of irregular nodular carbides, resulting in a significant drop in the flashover voltage (V _f ) of the dielectric (up to 75.0%, as shown in Figure 6).

The degree of arc damage of EP#1 and EP#4 has been significantly improved. As shown in Figure 5(b) and (c), the severe carbonization on the surface of the sample transformed into relatively uniform local slight damage, and the carbonization area decreased by 86.5% compared with EP#0; and the surface of the composite medium showed a The clear long-range ordered structure shows that the prepared three-dimensional framework can still be relatively intact in the EP matrix even under the local high temperature of the arc, thereby effectively inhibiting the melting and decomposition of the matrix.

The creeping flashover voltage of EP#4 is 15.0% higher than that of EP#0. However, after arc damage, the electrical resistance along the surface of 3DBNNS/EP composite medium increases significantly with the increase of BNNS concentration, and compared with EP#4 and EP#1~3, the introduction of glass fiber will not damage the 3D-BNNS/EP composite medium Intrinsic electrical resistance along the surface and excellent arc resistance, as shown in the bar graph in Figure 6.

(2) Thermal infrared image and surface temperature change trend test

The damage of the arc to the solid insulating medium is mainly caused by the thermal effect during the arcing process. The degree of damage of the medium under the action of the arc heat flow, that is, the arc resistance performance, is closely related to its own thermal conductivity. In order to more intuitively reflect the thermal response characteristics of different EP composite media at high temperatures, a thermal infrared imager (FLIR One Pro) was used to record and analyze the heating process of the samples prepared in Examples 10-12 and the cooling process after arc action .

The thermal infrared images and surface temperature change trends of EP#0, EP#1 and EP#4 are shown in Figure 7.

The results show that the two composite media of 3D-BNNS/EP and 3D-eGF&BNNS/EP can significantly improve the thermal management ability of EP insulating media due to the three-dimensional ordered framework of BNNS with high thermal conductivity impregnated in the matrix, which can quickly absorb or dissipate Heat, so that the temperature of the medium quickly reaches the ambient temperature.

Example 13 Mechanical Strength Improvement Test of 3D-eGF&BNNS/EP

Considering the actual application conditions of EP insulation medium in the fracture insulation of high-voltage DC circuit breakers, this example uses the samples prepared in Examples 1 to 3, and refers to the test method recommended in the GB/T 1040.2-2006 standard, using a universal tensile testing machine (Tinius Olsen Testing Machine Company, model H25KL) was used to test the tensile strength of the sample, and in the process, the deformation state of the sample was photographed in real time with a high-resolution electron microscope, and then with the help of the Ncorr numerical image analysis program (Digital Image Correlation ) to investigate the strain distribution of the sample under tensile loading.

The stress-strain curves and tensile strengths of the media of EP#1 to EP#4 are shown in Figure 8.

The results show that the mechanical properties of 3D-BNNS/EP composite media are significantly improved after introducing epoxy group-grafted eGF into the three-dimensional ordered framework of BNNS, and can be obtained when the mass ratio of eGF/BNNS is only 0.5:1. Mechanical strength and ductility superior to pure EP media. When the mass ratio of eGF/BNNS was increased to 1:1, the tensile strength of 3D-eGF&BNNS/EP composite media reached 97.04 MPa, which was 85.5% higher than that of pure EP media.

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (11)

1. a kind of preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin, is characterized in that, described method comprises the following steps: s1. Stripping of hexagonal boron nitride: add hexagonal boron nitride into an organic solvent for ultrasonic dispersion treatment for 35~50h, after standing still, take the upper suspension and undergo multiple centrifugation, and the obtained supernatant is suction filtered, and the The precipitate obtained by suction filtration is dried, and the exfoliated h-BN nanosheet sample is obtained as BNNS; s2, surface chemical grafting of glass fibers: adding glass fibers to piranha etching solution, washing to neutrality after stirring and drying to obtain treated glass fibers; adding the treated glass fibers to NaOH solution and Fully stir in the mixed solution of epichlorohydrin EPI; then wash and dry sequentially to obtain the glass fiber sample eGF grafted with epoxy on the surface; s3. The stripped h-BN nanosheet and the glass fiber sample grafted with epoxy on the surface: BNNS and sodium carboxymethylcellulose SCMC were mixed with water to obtain a BNNS/SCMC suspension; the eGF was uniformly dispersed in water to obtain eGF suspension; Wherein: BNNS concentration in BNNS/SCMC suspension is 1~20wt%, SCMC concentration is 0.1~5wt%; s4. Preparation of eGF&BNNS three-dimensional ordered framework: blend the BNNS/SCMC suspension and eGF suspension in s3, stir at 70-90°C for 4-6 h, pour into a mold, and place in liquid nitrogen Carry out directional freezing; finally, transfer the frozen sample into a freeze dryer for freeze-drying to obtain the dried eGF&BNNS three-dimensional ordered framework; Among them: the freeze-drying condition is that the temperature is -100~-50°C, the pressure is ≤0.5 Pa, and the freeze-drying time is 24~72h; the mass ratio of eGF to BNNS is 0.5~5:1; s5. Preparation of eGF&BNNS three-dimensional ordered framework impregnated with epoxy resin: use matrix, curing agent and accelerator to prepare mixed solution, immerse the eGF&BNNS three-dimensional ordered framework prepared in s4 into the evenly stirred mixed solution; After fully impregnated under pressure and vacuum, the compound is solidified by gradient temperature rise to obtain the epoxy resin sample EP of eGF&BNNS three-dimensional ordered framework, and the matrix is epoxy resin. 2. the glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework composite epoxy resin preparation method according to claim 1, is characterized in that, in s2, the condition of sufficient stirring is to stir under the condition that temperature is 90～100 ℃ 0.5~1.5h. 3. glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework composite epoxy resin preparation method according to claim 2, is characterized in that, in s2, the concentration of NaOH solution is 1～3 mol/L; Treated GF , The mass volume ratio between NaOH solution and epichlorohydrin EPI is 50~60g: 5~15 mL: 3~8 mL. 4. the preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin according to claim 1, is characterized in that: in s3, BNNS concentration is 3～15wt% in BNNS/SCMC suspension, The concentration of SCMC is 0.1-2wt%, and the concentration of eGF in the eGF suspension is 15-30wt%. 5. The preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin according to claim 1, characterized in that: in s4, the freeze-drying condition is that the temperature is -90~-70°C, the pressure Less than 0.1~0.5 Pa, the freeze-drying time is 40~50h; the mass ratio of eGF to BNNS is 0.5~2:1. 6. the preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin according to claim 1, is characterized in that: take DGEBA epoxy resin as matrix, methyltetrahydrophthalic anhydride (MTHPA) in s5 It is the curing agent, and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) is the accelerator. 7. according to the preparation method of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered framework composite epoxy resin described in claim 1 or 5, it is characterized in that: in s5, the three mass ratios of matrix, curing agent and accelerator are 100:70~90:1~5, the base is epoxy resin. 8. The preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin according to claim 1, characterized in that: in s5, the curing condition is 85~95°C for 1~3 hours, 100 Curing at ~120℃ for 1~3 hours. 9. The preparation method of glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin according to claim 1, characterized in that: in s5, the mass ratio of eGF & BNNS three-dimensional ordered frame to the mixed solution is 0.1 ~ 0.3 :1. 10. A glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin, characterized in that the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin adopts any one of claims 1 to 8 Prepared by the preparation method described in the claim. 11. The application of the glass fiber reinforced hexagonal boron nitride three-dimensional ordered frame composite epoxy resin prepared by the method according to any one of claims 1-8 in the field of electrical insulation.