阅读说明：本技术 一种交替多层结构的复合电介质材料及其制备方法 (Composite dielectric material with alternating multilayer structure and preparation method thereof ) 是由 廖煜 李瑞江 董晓聪 冯凌露 黄鑫 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种交替多层结构的复合电介质材料,属于电介质高分子材料技术领域,所述复合电介质材料由聚合物层与复合层交替层叠而成；将无机粒子与接枝活性基团的聚合物进行熔融共混形成核壳包覆结构的复合材料,并利用该复合材料与聚合物进行熔融挤出得到三元复合材料,最后通过三元复合材料与聚合物经过微纳共挤制备了具有交替多层结构的复合电介质材料,并利用该材料制备了复合材料薄膜,本发明的复合材料介电常数高,可以达到20以上；抗电强度高,可以达到500V/μm以上；储能密度高,50Hz频率下,储能密度最高可达为9.34J/cm<Sup>3</Sup>,在100Hz电场频率下,储能密度可达8.5J/cm<Sup>3</Sup>,其能量释放效率达到95％以上,同时所获得的材料可以通过双向拉伸得到厚度5-30μm的薄膜材料,具有市场应用前景。(The invention discloses a composite dielectric material with an alternative multilayer structure, belonging to the technical field of dielectric high polymer materials, wherein the composite dielectric material is formed by alternately laminating polymer layers and composite layers; the preparation method comprises the steps of carrying out melt blending on inorganic particles and a polymer grafted with an active group to form a composite material with a core-shell coating structure, carrying out melt extrusion on the composite material and the polymer to obtain a ternary composite material, finally carrying out micro-nano co-extrusion on the ternary composite material and the polymer to prepare a composite dielectric material with an alternating multilayer structure, and preparing a composite material film by using the composite material, wherein the composite material has a high dielectric constant which can reach more than 20; the electric strength is high and can reach more than 500V/mum; the energy storage density is high, and the highest energy storage density can reach 9.34J/cm under the frequency of 50Hz 3 Under the electric field frequency of 100Hz, the energy storage density can reach 8.5J/cm 3 The energy release efficiency of the material reaches more than 95 percent, and meanwhile, the obtained material can be stretched in two directions to obtain a thin film material with the thickness of 5-30 mu m, so that the material has market application prospect.)

1. A composite dielectric material of alternating multilayer structure, characterized by: the composite dielectric material is formed by alternately laminating polymer layers and composite layers;

the composite layer is composed of polymers, modified polymers and inorganic particles, wherein the modified polymers account for 1-50% of the composite layer by volume; the inorganic particles account for 0.1-25% of the composite layer by volume.

2. The composite dielectric material of the alternating multilayer structure of claim 1, wherein: the number of layers of the composite dielectric material is 2-512 layers, and preferably 32-128 layers.

3. The composite dielectric material of the alternating multilayer structure of claim 1, wherein the polymer is selected from one of vinylidene fluoride, polypropylene, polyvinyl chloride, polystyrene, or polyethylene terephthalate, preferably vinylidene fluoride or polypropylene.

4. The composite dielectric material of claim 1, wherein the modified polymer is a polymer material having active chemical groups grafted to the ends or branches of the polymer matrix molecules.

5. The composite dielectric material of the alternating multilayer structure of claim 4, wherein the reactive chemical group is at least one of maleic anhydride, methacrylic acid group, hydroxyl group, carboxylic acid, aldehyde group, amino group, isocyanate, preferably maleic anhydride or methacrylic acid group.

6. The composite dielectric material of claim 4, wherein the graft ratio of the graft active chemical group polymer is 1-10%, preferably 1-5%.

7. The composite dielectric material of the alternating multilayer structure of claim 1, wherein the inorganic particles are modified inorganic particles modified with a siloxane coupling agent; the siloxane coupling agent is selected from one of 3- (trimethoxysilyl) propyl methacrylate, gamma-methacryloxypropyltrimethoxysilane, 3- (2, 3-epoxypropoxy) propyltrimethoxysilane and 3-isocyanatopropyltrimethoxysilane.

8. The composite dielectric material of the alternating multilayer structure of claim 1, wherein the inorganic particles are selected from barium titanate, barium strontium titanate, zirconium oxide, silicon oxide, magnesium oxide, aluminum oxide, preferably zirconium oxide and barium titanate, having a particle size of 10-150nm, preferably 10-80 nm.

9. The method of making an alternating multilayer structured composite dielectric material of any of claims 1 to 8, comprising the steps of:

1) mixing inorganic particles with absolute ethyl alcohol or methanol according to a volume ratio of 1: 1-1: 5, mixing, performing ultrasonic dispersion, adding a siloxane coupling agent with the same mass as the inorganic particles for surface modification treatment, performing ultrasonic activation on the surfaces of the inorganic particles, repeatedly filtering, washing and filtering the obtained suspension, and drying to obtain modified inorganic particles;

2) mixing the modified inorganic particles obtained in the step 1) with the modified polymer macromolecules according to a volume ratio of 1: 200-1: 1, mixing, melting, blending and extruding at 35-45r/min and 185 ℃ of 175-;

3) mixing the master batch prepared in the step 2) with a polymer according to a volume ratio of 1: 100-1: 1, mechanically mixing, and melting, blending and extruding under the conditions of 35-45r/min and 185 ℃ of 175-;

4) respectively adding a polymer and the ternary composite material prepared in the step 3) into material inlet A and material inlet B of a micro-nano co-extrusion device, changing the arrangement of a layer number multiplier in the device, and preparing composite dielectric medium composite material semi-finished products with different layer thickness ratios and different layer numbers and an alternative multilayer structure by a micro-nano co-extrusion technology; the layer thickness ratio is 3: 1-1: 3, preferably 2:1 to 1: 2;

5) preparing the composite dielectric film material with an alternating multilayer structure from the obtained membrane by adopting a biaxial stretching method; the stretching temperature is 140-.

Technical Field

The invention relates to the technical field of composite dielectric materials, in particular to a composite dielectric material with an alternating multilayer structure and a preparation method thereof.

Background

Polymer dielectric materials are widely used due to their advantages of high dielectric strength, low loss, high energy storage density, etc. With the continuous development of power electronic technology, the demand for various high-power devices is increasing day by day, the power electronic film capacitor has the advantages of high voltage, high energy storage density, ultrahigh pulse power, rapid charge and discharge, stable performance and the like, and the power capacitor is widely applied as an energy storage unit, including high-power frequency converters, alternating current transmission systems of main line railway rolling stocks, vehicles outside urban rail transit rolling stocks and other military fields. However, the development of the electronic industry, especially the miniaturization development of the high energy storage power industry, puts higher requirements on the low loss and high energy storage density of the dielectric material, but because the dielectric constants of the current commercial PP and PET are less than 3, the energy storage density is low, and the requirement of the power electronic industry on the high energy storage density of the product is difficult to meet.

Meanwhile, the inorganic ceramic particles have the characteristics of high dielectric constant and low dielectric strength, so that the advantages of the inorganic particles and the advantages of the polymer matrix are combined to develop the composite material, and the advantages of the inorganic particles and the polymer matrix are complemented.

At present, the composite dielectric material is mainly prepared by dispersing inorganic particles with high dielectric constant in a polymer matrix by a method of melt blending and solution blending. For example, in the article of 'research on dielectric and piezoelectric properties of PZT/PVDF piezoelectric composite material', PVDF and barium titanate are melted and blended to prepare a composite material with a high dielectric constant, but because inorganic particles are difficult to be uniformly distributed in a PVDF matrix, the inorganic particles are easy to form agglomeration in the material matrix, so that the processing performance of the material is poor, the obtained material cannot be processed into a film material, and the practicability is poor. For another example, the 'a polymer-based dielectric material having a multilayer structure and a method for preparing the same' 200910083691.5 patent uses a solution blending method to obtain a composite material having a three-layer structure through a coating process, but since it is difficult to uniformly and stably disperse inorganic particles in a polymer matrix in order to solve the problem of agglomeration of the inorganic particles in the polymer matrix, a sample having a thickness of 90 to 150 μm can be obtained only by a hot pressing method, and a commercial dielectric thin film material having a thickness of 2 to 10 μm cannot be obtained by a stretching method, it is difficult to practically apply the material to products.

At present, the reported composite dielectric material is mostly prepared by a solution method or a melt blending method, and the problem that inorganic nanoparticles are easy to agglomerate in a polymer matrix is difficult to solve, so that the dielectric composite material has low dielectric strength. 201711382194.6, the breakdown field strength of the composite dielectric material with the zirconia addition amount of 5 percent is only 400V/mum, thereby leading the energy storage density to be lower, and simultaneously, the patent can only obtain a film experimental sample by a hot pressing method.

Therefore, how to solve the problems of low dielectric constant, large film thickness and low energy storage density of the dielectric composite material in the prior art at the same time is a problem which is always attempted to be solved but not solved in the field.

Disclosure of Invention

It is an object of the present invention to provide a composite dielectric material with an alternating multi-layer structure to solve the above problems.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a composite dielectric material with an alternating multilayer structure is formed by alternately laminating polymer layers and composite layers;

the composite layer is composed of polymers, modified polymers and inorganic particles, wherein the modified polymers account for 1-50% of the composite layer by volume, and the inorganic particles account for 0.1-25% of the composite layer by volume.

As a preferred technical scheme: the number of layers of the composite dielectric material is 2-512, and the preferable number of layers is 32-128.

As a preferred technical solution, the polymer is selected from one of vinylidene fluoride PVDF, polypropylene PP, polyvinyl chloride PVC, polystyrene PS or polyethylene terephthalate PET, preferably vinylidene fluoride or polypropylene.

As a preferable technical scheme, the modified polymer is a high molecular material of which the polymer matrix molecule end or branch is grafted with an active chemical group.

As a further preferable technical scheme, the active chemical group is maleic anhydride MAH, methacrylic acid MMA, hydroxyl OH, carboxylic acid COOH, aldehyde group CHO, amino NH₂And/or isocyanate NC, preferably maleic anhydride or methacrylic acid group, and the graft ratio is 1 to 10%.

As a further preferable technical scheme, the grafting rate of the grafting active chemical group polymer is 1-5%.

As a preferred technical scheme, the inorganic particles are modified inorganic particles modified by adopting a siloxane coupling agent; the siloxane coupling agent is selected from one of 3- (trimethoxysilyl) propyl methacrylate (KH570), gamma-methacryloxypropyltrimethoxysilane (G570), 3- (2, 3-glycidoxy) propyltrimethoxysilane (KH560) and 3-Isocyanatopropyltrimethoxysilane (IPTS), and is preferably KH 570.

Preferably, the inorganic particles are selected from barium titanate BaTiO₃Barium strontium titanate Ba_xSr_1-xTiO₃Strontium titanate SrTiO₃Zirconium oxide ZrO₂Silicon oxide SiO₂MgO, magnesium oxide₂Aluminum oxide Al₂O₃Zirconium oxide and barium titanate are preferred, and the particle size of the inorganic particles is 10 to 150nm, preferably 10 to 80 nm.

The second objective of the present invention is to provide a method for preparing the composite dielectric material with the alternating multilayer structure, which adopts a technical scheme that the method comprises the following steps:

1) mixing inorganic particles with absolute ethyl alcohol or methanol according to a volume ratio of 1: 1-1: 5, mixing, performing ultrasonic dispersion, adding a siloxane coupling agent with the same mass as the inorganic particles for surface modification treatment, performing ultrasonic activation on the surfaces of the inorganic particles, repeatedly filtering, washing and filtering the obtained suspension, and drying to obtain modified inorganic particles;

2) mixing the modified inorganic particles obtained in the step 1) with the modified polymer macromolecules according to a volume ratio of 1: 200-1: 1, mixing, melting, blending and extruding at 35-45r/min and 185 ℃ of 175-;

3) mixing the master batch prepared in the step 2) with a polymer machine according to a volume ratio of 1: 100-1: 1, mixing, and melting, blending and extruding under the conditions of 35-45r/min and 185 ℃ of 175-;

4) respectively adding a polymer and the ternary composite material prepared in the step 3) into material inlet A and material inlet B of a micro-nano co-extrusion device, changing the arrangement of a layer number multiplier in the device, and preparing composite dielectric medium composite material semi-finished products with different layer thickness ratios and different layer numbers and an alternative multilayer structure by a micro-nano co-extrusion technology; the layer thickness ratio is 3: 1-1: 3, preferably 2:1 to 1: 2;

5) performing biaxial tension on the obtained membrane to obtain a composite dielectric film material with an alternating multilayer structure; the stretching temperature is 140-180 ℃, the stretching ratio is 200-600%, preferably 300-450%, and the composite dielectric film material with the thickness of 5-30 μm and the alternating multilayer structure is obtained.

According to the invention, firstly, the ternary composite material with a core-shell structure is prepared from modified inorganic particles and polymers grafted with active groups by a traditional melt blending method, and then the ternary composite material and the polymers are subjected to micro-nano co-extrusion, namely, melt blending and micro-nano co-extrusion are organically combined innovatively, a polymer layer and an organic-inorganic composite layer alternately exist in the material, wherein an inorganic filler with a high dielectric constant is added into the composite layer to improve the dielectric constant of the material, the inorganic nano filler is changed into two-dimensional distribution from original three-dimensional free distribution due to the limiting effect of the polymer layer, and the space agglomeration of inorganic nano particles is reduced, so that the problem of the reduction of the electric strength of the material caused by electric field distortion due to the agglomeration of the inorganic particles is solved. Meanwhile, when the polymer layer and the filler layer are alternately arranged in an electric field, the polymer layer can effectively block internal current carriers so as to improve the space volume resistivity of the dielectric material, and the organic-inorganic composite dielectric material with high dielectric constant and high dielectric strength and an alternate multilayer structure is obtained.

Compared with the prior art, the invention has the advantages that: the composite material provided by the invention has high dielectric constant which can reach more than 20; high electric strength up to 500V/mum is more than m; the energy storage density is high, and the highest energy storage density can reach 9.34J/cm under the frequency of 50Hz³Under the electric field frequency of 100Hz, the energy storage density can reach 8.5J/cm³The energy release efficiency of the material reaches more than 95 percent, and meanwhile, the obtained material can be stretched in two directions to obtain a film material with the thickness of 15-30 mu m, so that the material has market application prospect.

Drawings

FIG. 1 is an SEM image of a composite dielectric material prepared in example 1;

FIG. 2 is an optical micrograph of a cross section of a composite dielectric material obtained in example 1;

FIGS. 3-6 are graphs showing the dielectric properties of the composite dielectric material prepared in example 1, with frequency on the abscissa, dielectric constant on the left ordinate, and dielectric loss on the right ordinate; wherein FIGS. 3-1 and 3-2 show the effect of MAH content on dielectric constant, FIG. 4 shows the effect on dielectric constant before and after modification of inorganic particles, FIGS. 5-1 and 5-2 show the dielectric properties of different number of layers and inorganic particle content, and FIG. 6 shows the dielectric properties of different layer-to-thickness ratios;

FIG. 7 is a hysteresis loop plot at high electric field for the composite dielectric material prepared in example 1;

FIG. 8 shows the dielectric strength resistance results of the composite dielectric material obtained in example 1;

FIG. 9 is a graph showing the energy storage density of the composite dielectric material prepared in example 1;

FIG. 10 is an optical micrograph of a cross section of a composite dielectric material obtained in example 2;

FIG. 11 shows the dielectric constant of the composite dielectric material obtained in example 2;

FIG. 12 is a hysteresis loop at high electric field for the composite dielectric material prepared in example 2;

in the figure, a is 32L-1: 1-15%; b, 32L-2: 1-15%; c, 32L-1: 1-5%; d, 64L-1: 1-5%; e, 64L-1: 1-15%;

FIG. 13 shows dielectric strength of the composite dielectric material obtained in example 2,

in the figure, a is 32L-1: 1-15%; b, 32L-2: 1-15%; c, 32L-1: 1-5%; d, 64L-1: 1-5%; e, 64L-1: 1-15%; ) (ii) a

FIG. 14 is a graph of the energy storage density of the composite dielectric material prepared in example 2;

Detailed Description

The invention will be further explained with reference to the drawings.