阅读说明：本技术 一种gnp/ps-bt/pvdf选择性复合薄膜及其制备方法 (GNP/PS-BT/PVDF selective composite film and preparation method thereof ) 是由 王继华 张明婷 韩志东 王春锋 王永亮 于 2021-07-15 设计创作，主要内容包括：一种GNP/PS-BT/PVDF选择性复合薄膜及其制备方法。本发明属于介电材料及其制备领域。本发明的目的是解决现有聚合物基高介电常数复合材料损耗因子高、绝缘性能差的技术问题。本发明的一种GNP/PS-BT/PVDF选择性复合薄膜由BT/PVDF复合材料和GNP/PS复合材料经粉碎、混炼和热压而成,所述GNP/PS-BT/PVDF选择性复合薄膜为具有微电容器结构的四元复合薄膜；其中BT/PVDF复合材料由BT和PVDF混炼而成,GNP/PS复合材料由GNP和PS混炼而成。方法：分别先预混形成GNP/PS复合材料和BT/PVDF复合材料,然后再将两种复合材料粉碎后混炼,再进行热压,冷却后得到GNP/PS-BT/PVDF选择性复合薄膜。本发明的复合材料内部具有微电容器结构,在保证介电常数显著提高的同时仍保持较高的击穿场强和优异的综合性能。(A GNP/PS-BT/PVDF selective composite film and a preparation method thereof. The invention belongs to the field of dielectric materials and preparation thereof. The invention aims to solve the technical problems of high loss factor and poor insulating property of the existing polymer-based high-dielectric-constant composite material. The GNP/PS-BT/PVDF selective composite film is formed by crushing, mixing and hot-pressing a BT/PVDF composite material and a GNP/PS composite material, and is a quaternary composite film with a micro-capacitor structure; the BT/PVDF composite material is formed by mixing BT and PVDF, and the GNP/PS composite material is formed by mixing GNP and PS. The method comprises the following steps: and respectively premixing to form a GNP/PS composite material and a BT/PVDF composite material, then crushing and mixing the two composite materials, then carrying out hot pressing, and cooling to obtain the GNP/PS-BT/PVDF selective composite film. The composite material has a micro-capacitor structure inside, and the dielectric constant is remarkably improved, and meanwhile, higher breakdown field strength and excellent comprehensive performance are still maintained.)

1. The GNP/PS-BT/PVDF selective composite film is characterized in that the composite film is formed by crushing, mixing and hot-pressing a BT/PVDF composite material and a GNP/PS composite material, and the GNP/PS-BT/PVDF selective composite film is a quaternary composite film with a micro-capacitor structure; the BT/PVDF composite material is formed by mixing BT and PVDF, and the GNP/PS composite material is formed by mixing GNP and PS.

2. The GNP/PS-BT/PVDF selective composite film according to claim 1, wherein the mass fraction of BT in the GNP/PS-BT/PVDF selective composite film is 40% -60%, and the balance is the sum of the masses of GNP, PS and PVDF.

3. The GNP/PS-BT/PVDF selective composite film according to claim 2, wherein the sum of the masses of GNP, PS and PVDF is 0.05-1.2% by mass, and the balance is the sum of the masses of PS and PVDF.

4. A GNP/PS-BT/PVDF selective composite film according to claim 3, wherein the sum of the masses of PS and PVDF is (4-7): 4.

5. the method for preparing a GNP/PS-BT/PVDF selective composite film according to any of claims 1-4, which comprises the following steps:

step 1: mixing PS and GNP to obtain a GNP/PS composite material;

step 2: mixing PVDF and BT to obtain a BT/PVDF composite material;

and step 3: respectively crushing the GNP/PS composite material and the BT/PVDF composite material, mixing the crushed two composite materials, and then mixing to obtain a GNP/PS-BT/PVDF blended material;

and 4, step 4: preheating the GNP/PS-BT/PVDF blended material, then carrying out hot pressing, and cooling to obtain the GNP/PS-BT/PVDF selective composite film.

6. The method for preparing a GNP/PS-BT/PVDF selective composite film according to claim 5, wherein the mixing parameters in step 1, step 2 and step 3 are the same, the mixing temperature is 185-195 ℃, and the mixing time is 20-40 min.

7. The method for preparing a GNP/PS-BT/PVDF selective composite film according to claim 6, wherein the mixing parameters in step 1, step 2 and step 3 are the same, the mixing temperature is 190 ℃ and the mixing time is 30 min.

8. The preparation method of the GNP/PS-BT/PVDF selective composite film according to claim 5, wherein the preheating temperature in step 4 is 180-190 ℃ and the preheating time is 15-25 min.

9. The preparation method of the GNP/PS-BT/PVDF selective composite film according to claim 5, wherein the hot-pressing temperature in step 4 is 180-190 ℃, the hot-pressing pressure is 9-11 MPa, and the pressure holding time is 8-12 min.

10. The method for preparing a GNP/PS-BT/PVDF selective composite membrane according to claim 9, wherein the hot-pressing temperature in step 4 is 185 ℃, the hot-pressing pressure is 10MPa, and the dwell time is 10 min.

Technical Field

The invention belongs to the field of dielectric materials and preparation thereof, and particularly relates to a GNP/PS-BT/PVDF selective composite film and a preparation method thereof.

Background

In order to meet the requirements of the electronic information era on miniaturization and light weight of electronic equipment, which is rapidly developed, a dielectric material with higher dielectric constant and lower dielectric loss needs to be prepared.

The introduction of high dielectric constant ceramics and conductive materials is a common method for obtaining polymer-based high dielectric constant composite materials at present, but problems such as increase of loss factor and reduction of insulating property are brought with the introduction of high dielectric constant ceramics and conductive materials, and although research on compounding, modification, structural design and the like of fillers is advanced to a certain extent at present, methods for comprehensively improving the dielectric constant, loss factor, insulation resistance and dielectric strength of polymer-based dielectric composite materials still need to be researched.

Disclosure of Invention

The invention aims to solve the technical problems of high loss factor and poor insulating property of the existing polymer-based high-dielectric-constant composite material, and provides a GNP/PS-BT/PVDF selective composite film and a preparation method thereof.

The GNP/PS-BT/PVDF selective composite film is formed by crushing, mixing and hot-pressing a BT/PVDF composite material and a GNP/PS composite material, and is a quaternary composite film with a micro-capacitor structure; the BT/PVDF composite material is formed by mixing BT and PVDF, and the GNP/PS composite material is formed by mixing GNP and PS.

Further limiting, the mass fraction of BT in the GNP/PS-BT/PVDF selective composite film is 40-60%, and the balance is the sum of the mass of GNP, PS and PVDF.

Further limiting, the mass fraction of BT in the GNP/PS-BT/PVDF selective composite film is 50%, and the balance is the sum of the mass of GNP, PS and PVDF.

Further limited, the sum of the mass of the GNP, the mass of the PS and the mass of the PVDF is 0.05-1.2%, and the balance is the sum of the mass of the PS and the mass of the PVDF.

Further defined, the sum of the masses of the GNP, the PS and the PVDF is that the mass fraction of the GNP is 0.05 percent, and the balance is the sum of the masses of the PS and the PVDF.

Further limiting, the mass ratio of PS to PVDF in the sum of the masses of PS and PVDF is (4-7): 4.

further defined, the sum of the masses of PS and PVDF has a mass ratio of PS to PVDF of 6: 4.

the preparation method of the GNP/PS-BT/PVDF selective composite film is carried out according to the following steps:

step 1: mixing PS and GNP to obtain a GNP/PS composite material;

step 2: mixing PVDF and BT to obtain a BT/PVDF composite material;

and step 3: respectively crushing the GNP/PS composite material and the BT/PVDF composite material, mixing the crushed two composite materials, and then mixing to obtain a GNP/PS-BT/PVDF blended material;

and 4, step 4: preheating the GNP/PS-BT/PVDF blended material, then carrying out hot pressing, and cooling to obtain the GNP/PS-BT/PVDF selective composite film.

Further limiting, the mixing parameters in the step 1, the step 2 and the step 3 are the same, the mixing temperature is 185-195 ℃, and the mixing time is 20-40 min.

Further limiting, the mixing parameters in the step 1, the step 2 and the step 3 are the same, the mixing temperature is 190 ℃, and the mixing time is 30 min.

Further limiting, the preheating temperature in the step 4 is 180-190 ℃, and the preheating time is 15-25 min.

Further limiting, the hot pressing temperature in the step 4 is 180-190 ℃, the hot pressing pressure is 9-11 MPa, and the pressure maintaining time is 8-12 min.

Compared with the prior art, the invention has the advantages that:

the invention adopts incompatible Polystyrene (PS) and polyvinylidene fluoride (PVDF) as matrix resin, uses GNP (graphene) and BT (barium titanate) as fillers, utilizes a blending method to prepare a blending system of the composite fillers, designs and forms a microcosmic controllable phase structure, explores an interaction mechanism between the fillers and a matrix in different composite systems, establishes a structure-effect system between the structure and the dielectric property of a polymer-based dielectric material, explores whether the material can still maintain higher breakdown field strength while ensuring the dielectric constant to be obviously improved, provides a certain theoretical basis and design guidance for the research and development of the polymer-dielectric composite material, and has the following specific advantages:

1) the invention effectively overcomes the defect of a single component by forming a heterogeneous polymer blending system by two incompatible polymers, and improves various performances of the high polymer material by the synergistic effect of a dispersed phase structure and a co-continuous phase structure.

2) The system of the invention utilizes the characteristic that the filler is selectively distributed in one of the polymer phases or at the interface of the two phases, thereby obviously improving the dielectric property and the mechanical property of the polymer. The conductive filler is used in the incompatible polymer blend to form a selective distribution structure, so that the percolation threshold can be reduced, the conductivity of the composite material can be improved at a lower filler content, and the blend system with the co-continuous phase structure can obtain good conductivity at a lower conductive filler content.

3) The hot-pressing process can realize the parallel and uniform distribution of the two-dimensional lamellar GNP in the matrix, thereby forming a certain number of micro-capacitor structures, and being beneficial to greatly improving the dielectric property of the material.

4) The quaternary composite system of the invention has coexistence of various polarization effects, the synergistic effect of BT and GNP can inhibit the increase of dielectric loss to a certain extent, and simultaneously the microscopic capacitor structure in the matrix is the same as the macroscopic multilayer structure in design, thus further improving the dielectric constant.

5) The method of the invention mixes the two groups of completely pre-dispersed composite systems again after crushing, which can reflect the selective distribution characteristics of the filler more fully, and the selection of mixing parameters is beneficial to the uniform distribution of the filler.

6) The selective blending method of the invention has the frequency of more than 10⁵In Hz, the dielectric loss of the composite system with the selectively distributed filler is only 0.09 at most, the breakdown strength of the composite system with the selectively distributed filler is higher than that of a direct and inverse blending system, the distribution range of the breakdown field intensity is narrow, and the reliability of the material is improved.

Drawings

FIG. 1 is a SEM topographic structure diagram of the GNP/PS-BT/PVDF selective composite film of example 1;

FIG. 2 is a SEM topographic map of magnification of the GNP/PS-BT/PVDF selective composite membrane of example 1;

FIG. 3 is a schematic structural diagram of a micro-capacitor of the GNP/PS-BT/PVDF selective composite film of example 1;

FIG. 4 is a SEM topography structure diagram of the GNP/PS/BT/PVDF composite film of comparative example 1;

FIG. 5 is a SEM topography structure diagram of the BT/PS-GNP/PVDF composite film of comparative example 2;

FIG. 6 is a graph showing the variation of dielectric constant with frequency for the composite materials of example 1 and comparative examples 1 to 5;

FIG. 7 is a graph of the conductivity versus frequency for the composites of example 1 and comparative examples 1-5;

FIG. 8 is a graph of the dielectric dissipation factor as a function of frequency for the composite materials of example 1 and comparative examples 1-5;

FIG. 9 is a graph comparing the breakdown field strength of the composites of example 1 and comparative examples 1, 6-7; where a is the breakdown field strength fit plot and b is the characteristic breakdown field strength.

Detailed Description

Example 1: the GNP/PS-BT/PVDF selective composite film is formed by crushing, mixing and hot-pressing a BT/PVDF composite material and a GNP/PS composite material, and is a quaternary composite film with a micro-capacitor structure; the BT/PVDF composite material is formed by mixing BT and PVDF, and the GNP/PS composite material is formed by mixing GNP and PS; the mass fraction of BT in the GNP/PS-BT/PVDF selective composite film is 50%, the balance is the sum of the masses of GNP, PS and PVDF, the mass fraction of GNP in the sum of the masses of GNP, PS and PVDF is 0.5%, the balance is the sum of the masses of PS and PVDF, and the mass ratio of PS to PVDF in the sum of the masses of PS and PVDF is 6: 4.

the method for preparing the GNP/PS-BT/PVDF selective composite film described in example 1 was performed as follows:

step 1: mixing PS and GNP for 20min at 190 ℃ to obtain a GNP/PS composite material;

step 2: mixing PVDF and BT for 20min at 190 ℃ to obtain a BT/PVDF composite material;

and step 3: respectively crushing the GNP/PS composite material and the BT/PVDF composite material, mixing the two crushed composite materials, and then mixing for 20min at 190 ℃ to obtain a GNP/PS-BT/PVDF blended material;

and 4, step 4: preheating the GNP/PS-BT/PVDF blended material at 185 ℃ for 20min, then hot-pressing at 185 ℃ and 10MPa for 10min, and cooling to obtain the GNP/PS-BT/PVDF selective composite film.

Comparative example 1: the composition of the composite film in this embodiment is completely the same as that of embodiment 1, except that the preparation method of the composite film is different, specifically:

step 1, mixing BT, GNP, PVDF and PS for 20min at 190 ℃ to obtain a GNP/PS/BT/PVDF composite material;

step 2: the GNP/PS/BT/PVDF composite material is crushed, then placed in a flat vulcanizing machine, preheated for 20min at 185 ℃, then hot-pressed for 10min at 185 ℃ and 10MPa, and cooled to obtain the GNP/PS/BT/PVDF composite film.

Comparative example 2: the composition of the composite film in this embodiment is completely the same as that of embodiment 1, except that the preparation method of the composite film is different, specifically:

step 1: mixing PS and BT for 20min at 190 ℃ to obtain a BT/PS composite material;

step 2: mixing PVDF and GNP for 20min at 190 ℃ to obtain a GNP/PVDF composite material;

and step 3: respectively crushing the BT/PS composite material and the GNP/PVDF composite material, mixing the crushed two composite materials, and then mixing for 20min at 190 ℃ to obtain a BT/PS-GNP/PVDF blended material;

and 4, step 4: the BT/PS-GNP/PVDF blended material is preheated at 185 ℃ for 20min, then hot-pressed at 185 ℃ and 10MPa for 10min, and cooled to obtain the BT/PS-GNP/PVDF composite film.

Comparative example 3: the GNP/PS/PVDF ternary composite material and the preparation method thereof of the embodiment are as follows:

the product is as follows: the weight fraction of GNP in the GNP/PS/PVDF ternary composite material is 0.5%, the balance is the sum of the weight of PS and PVDF, and the weight ratio of PS to PVDF in the sum of the weight of PS and PVDF is 6: 4;

the method comprises the following steps:

step 1, mixing GNP, PVDF and PS at 190 ℃ for 20min to obtain a GNP/PS/PVDF composite material;

step 2: and (2) crushing the GNP/PS/PVDF composite material, then placing the crushed GNP/PS/PVDF composite material in a flat vulcanizing machine, preheating the crushed GNP/PS/PVDF composite material for 20min at 185 ℃, then hot-pressing the crushed GNP/PS/PVDF composite material for 10min at 185 ℃ and 10MPa, and cooling the obtained product to obtain the GNP/PS/PVDF ternary composite material.

Comparative example 4; the BT/PS/PVDF ternary composite material and the preparation method thereof are as follows:

the product is as follows: the mass fraction of BT in the BT/PS/PVDF ternary composite material is 50%, the balance is the sum of the masses of PS and PVDF, and the mass ratio of PS to PVDF in the sum of the masses of PS and PVDF is 6: 4;

the method comprises the following steps:

step 1, mixing BT, PVDF and PS for 20min at 190 ℃ to obtain a BT/PS/PVDF composite material;

step 2: crushing the BT/PS/PVDF composite material, then placing the crushed BT/PS/PVDF composite material in a flat vulcanizing machine, preheating the crushed BT/PS/PVDF composite material for 20min at 185 ℃, then hot-pressing the crushed BT/PS/PVDF composite material for 10min at 185 ℃ and 10MPa, and cooling the obtained product to obtain the BT/PS/PVDF ternary composite material.

Comparative example 5: the PS/PVDF pure matrix composite material and the preparation method thereof are as follows:

the product is as follows: the mass ratio of PS to PVDF in the PS/PVDF pure matrix composite material is 6: 4;

the method comprises the following steps:

step 1, mixing PVDF and PS for 20min at 190 ℃ to obtain a PS/PVDF composite material;

step 2: the PS/PVDF composite material is crushed, then placed in a flat vulcanizing machine, preheated at 185 ℃ for 20min, then hot-pressed at 185 ℃ and 10MPa for 10min, and cooled to obtain the PS/PVDF pure matrix composite material.

Comparative example 6: this example differs from example 1 in that: the sum of the masses of PS and PVDF is such that the mass ratio of PS to PVDF is 4: 6. the other steps and parameters were the same as in example 1.

Comparative example 7: this example differs from comparative example 6 in that: the composite material was prepared in the same manner as in comparative example 1, except that the other steps and parameters were the same as in comparative example 6.

Test one: the cross-sectional morphology of the quaternary composite materials obtained in example 1 and comparative examples 1-2 was observed to obtain the cross-sectional morphology structures of the three quaternary composite materials shown in fig. 1-5. The distribution conditions of the dispersed phase and the continuous phase of the three composite systems are different under high magnification observation. As can be seen from fig. 1, the distribution of the dispersed phases GNP and BT can still be observed in the continuous phase. However, due to the obvious selective distribution behavior of the GNPs and the BT, the originally PVDF-coated BT and the PS-coated GNPs have the tendency of reselecting without being bound, so that the two-phase matrix is affected by the reselecting of the two fillers, and the incompatible interface and the continuous structure of the two phases become blurred, thereby causing the irregular layered interface to appear on the whole matrix interface. The introduction of the GNP and BT affects the viscosity and phase structure of the system, so that a plurality of BT/PVDF phases cannot be aggregated to form a larger dispersed phase structure, a large amount of BT/PVDF phases are dispersed in the GNP/PS phases with smaller phase sizes to form a part of a continuous phase, and the GNP/PS forms a main component of the continuous phase structure. As can be seen from fig. 2, the GNPs are distributed in the matrix in a state close to the micro-capacitance structure; as can be seen from fig. 4, BT in the dispersed phase in the direct composite system is distributed in the matrix in a spherical shape, while a distinct GNP lamella is also observed to be distributed in the matrix; the continuous phase PS and PVDF are compounded more uniformly and have no obvious interface. From fig. 5, it can be observed that GNPs are uniformly distributed in the PS phase, and no BT particles appear, and it can also be observed that a large number of BT particles are aggregated and distributed in the PVDF phase, in which no GNP sheets appear. GNP and BT are stable and uniform in respective selective matrixes, so that the method has the advantages that the two-phase distribution structure is obvious, the two-phase fillers are spatially staggered and interpenetrated, and the two fillers can be continuously distributed in respective matrix resins and have good dispersibility. The phase structure of the composite is influenced on the one hand by the GNP and BT selectivity distribution and on the other hand by the viscosity of the two phases in the composite. As can be seen from the comparison results, the two preparation methods of comparative example 1 and comparative example 2 form a more complex phase structure. The method of example 1 is more beneficial to the control of the phase structure, and both GNP and BT can well exist in the resin with respective selection tendencies and keep stable and uniform distribution states. It was also further confirmed that the selective distribution of the filler enables the two composite phases to coexist independently and continuously from each other. The filler has good compatibility with the selectively distributed matrix and can form a uniformly dispersed composite system.

Second test, the change of the dielectric properties with frequency and the breakdown field strength of the composite materials of example 1 and comparative examples 1 to 5 were studied, and as shown in fig. 6 to 8, it can be found from fig. 6 to 7 that, compared with the pure matrix system, the matrix dielectric constant and the conductivity of the doped particles are both increased, and the dielectric constant of the composite system with the selective distribution of the filler is improved most significantly compared with other composite systems and is improved by nearly 3 times compared with the pure matrix, because the filler is mixed with the matrix with the selective distribution thereof on the premise that the matrix is co-continuous, and can be uniformly and continuously distributed in the matrix, and at this time, the conductive filler can form a conductive phase, and the dielectric filler can form a conductive phaseAnd forming a dielectric phase, wherein the conductive phase and the dielectric phase form a spatial hybrid structure. As can be seen from fig. 7, the trend of the conductivity of each system along with the frequency change is substantially consistent, and the conductivity of the system with the added particles is only slightly increased at the same frequency, which indicates that the increase of the conductivity of the system is less influenced by the single filler or the composite filler and the mixing mode. The conductivity of each system at 10Hz was 10^-12About S/cm, 10⁷Conductivity at Hz of 10^-6S/cm, increased by about 6 orders of magnitude. As shown in fig. 8, the frequency is 10-10⁵The dielectric loss difference of each system is not obvious at Hz, and when the frequency is more than 10⁵The composite system of example 1 has a dielectric loss of only 0.09 at Hz, which is comparable to other systems, because good dispersion and continuity of both the filler and matrix are maintained when the matrix is continuous and the filler is selectively distributed, and the PVDF has α relaxation that generates relaxation loss at high frequencies, resulting in increased loss of the overall system.

And thirdly, testing the breakdown field strengths of the composite materials of the embodiment 1, the comparative example 1 and the comparative examples 6 to 7, wherein the result is shown in fig. 9, and as can be seen from fig. 9a), the breakdown field strength of the system of the embodiment 1 is obviously higher than that of the other three systems, which shows that the breakdown field strength is more closely distributed and the reliability is higher. The breakdown field strengths of the two systems of comparative examples 6 to 7 have no obvious advantages, and the distribution of the breakdown field strengths is relatively dispersed, which shows that the matrix phase is continuous, and the filler is pre-distributed in the selective matrix, so that the dispersibility of the filler in the matrix can be well improved, the defect points are reduced, and the breakdown field strengths are improved. The filler is pre-distributed in the selective matrix, so that the filler is continuously distributed in the matrix, the distribution range of breakdown points is narrowed, and the reliability of the material is improved. Comparison of the characteristic breakdown field strengths E0 of the systems of different composite forms is shown in FIG. 9b), the E0 of the system with selective distribution and a matrix resin ratio PS6/PVDF4 is significantly higher than the other three systems. This is because, after the matrix is selectively distributed, when the ratio of the matrix resin PS to the PVDF is 6/4, the system just forms phase continuity, because GNP and BT can be uniformly dispersed in PS and PVDF respectively and are in a continuous distribution state, so the structural defects of the whole system are reduced, and the breakdown field strength is increased.