Study On Preparation And Thermal Conductivity Of Liquid Crystalline Epoxy Fiber/BNNSs Composite Insulation Film

Liquid crystalline epoxy resin has the advantages of high cross-linking degree and high crystallinity.At the same time,it has good insulation and chemical corrosion resistance,which can make up for the shortcomings of traditional epoxy resin such as low toughness and poor heat resistance.However,the liquid crystalline epoxy resin still has the problem of urgently improving thermal conductivity.In this paper,the preparation method of liquid crystalline epoxy fiber film/BNNSs composite insulation film with good thermal conductivity and insulation properties is studied,and the mechanics,thermal conductivity and insulation properties of the composite fiber film are studied in depth.The main contents of the paper include:(1)The preparation method of liquid crystalline epoxy fiber/BNNSs composite insulation film was studied.An electrostatic spinning method and process for preparing a highly oriented liquid crystalline epoxy fiber film was developed,and the fiber oriented film was filled with BNNSs in combination with a vacuum suction filtration method.So a filled orientation type liquid crystalline epoxy fiber film/BNNSs composite insulation film was further prepared.The results showed that a lower concentration of liquid crystalline epoxy prepolymer solution could reduce the fiber diameter of the liquid crystalline epoxy fiber film and increased the degree of fiber orientation.BNNSs were well dispersed in the liquid crystalline epoxy fiber film,and adhered to the surface of the liquid crystalline epoxy fiber to fill the gap of the liquid crystalline epoxy fiber film.Filling the fiber film with BNNSs helped to improve the tensile strength of the composite fiber film.(2)The effects of liquid crystalline epoxy fiber diameter and BNNSs filling concentration on the mechanical and electrical properties of liquid crystalline epoxy fiber film/BNNSs composite insulation film were studied.The results showed that the thinner the fiber diameter of the liquid crystalline epoxy fiber film,the lower the dielectric loss factor and the higher the volume resistivity.Increasing the filling amount of nano boron nitride could increase the relative dielectric constant and dielectric loss factor of the composite fiber film,but had little effect on the volume resistivity of the film.The thinner the fiber diameter of the liquid crystalline epoxy fiber films,the higher the AC breakdown strength.Filling the liquid crystalline epoxy fiber film with BNNSs can further improve the AC breakdown strength of the film and suppress the film thermal breakdown behavior.(3)The effects of the diameter of liquid crystalline epoxy fiber and the filling concentration of BNNSs on the thermal conductivity,thermal stability and dynamic mechanical properties of liquid crystalline epoxy fiber film/BNNSs composite insulation film were studied.The results showed that the thinner the fiber diameter,the higher the orientation of the film,the greater the cross-linking density,and the higher the in-plane thermal conductivity,but there was no significant difference in the through-plane thermal conductivity.With the increase of BNNSs filler content,the in-plane thermal conductivity of liquid crystalline epoxy fiber film/BNNSs composite insulation film was significantly increased,the through-plane thermal conductivity was also slightly increased,the thermal stability of liquid crystalline epoxy fiber film/BNNSs composite insulation film was enhanced.And the glass transition temperature was significantly increased.The above research results show that liquid crystalline epoxy fiber film/BNNSs composite insulation film prepared in this paper has excellent thermal conductivity,while maintaining good mechanical and electrical insulation properties.