Research On Preparation And Properties Of High Temperature Resistant Polyarylene Ether Nitrile Hybrids With High Dielectric Constant

With the rapid development of science and technology,high-quality film capacitors have been widely used in many fields such as new energy vehicles and communications by virtue of their advantages in frequency response and service life.Dielectric film is a significant part of film capacitors,its properties have an important influence on the performance and operating conditions of film capacitors.At present,the preparation of high dielectric constant films with high temperature resistance based on polymers is one of the key points in the research of dielectric films.The common method is to add fillers which can improve the dielectric constant to the polymer matrix with decent high temperature resistance.Improving the high temperature resistance of the film can ensure that the film capacitor can be used normally at high temperature environment and broaden the application range of the film capacitor,while the high dielectric constant can ensure that the film capacitor has a higher energy storage density under the same other conditions.Polyarylene ether nitrile(PEN)has benzene ring structure on the main chain,so it is a kind of polymer material with outstanding high temperature resistance.The side groups of the main chain contain polar cyano groups,and the dielectric constant is about 4.0.Adding fillers of specific properties to the PEN matrix can increase its dielectric constant,thereby achieving the purpose of preparing high temperature resistant and high dielectric constant films.In this paper,phthalonitrile end-capped crosslinkable PEN is used as the matrix,and cyanated one-dimensional bismuth sulfide(Bi₂S₃)nanorods,two-dimensional graphene oxide(GO)nanosheets and bismuth sulfide/reduced graphene oxide(Bi₂S₃/r GO)composite material of one-dimensional nanorods grown on the surface of two-dimensional nanosheets are added to the matrix.After forming the films by casting method,treat them at 340?for 4 hours to prepare hybrid films through the mutual reaction of cyano groups between the matrix and the filler.For comparative study,composite films without high temperature treatment were prepared according to the same proportion of filler content,and the properties of all the prepared films were tested.(1)One-dimensional Bi₂S₃ nanorods prepared by hydrothermal method were cyanated.After characterizing the products to confirm the effectiveness of the cyanation process,the nanorods were added as fillers to the PEN matrix to prepare film samples.The prepared polyarylene ether nitrile-bismuth sulfide(PEN-Bi₂S₃)hybrid films maintain the excellent high temperature resistance of PEN itself.The initial decomposition temperature is about 400?,and the highest glass transition temperature(T_g)reaches246.31?.At the same time,the addition of fillers did not affect the excellent mechanical properties of the PEN matrix.The tensile strengths of hybrid films are all above 80 MPa,and the tensile modulus are all above 2200 MPa.When the cyanated Bi₂S₃ nanorod filler content is 20 wt%,the dielectric constant of the hybrid film at 1 k Hz is increased by 59.0%compared with that of the pure film after high temperature treatment.The dielectric loss is maintained at a low level(less than 0.03)and the dielectric properties are relatively stable before 250?.(2)The polyarylene ether nitrile-graphene oxide(PEN-GO)hybrid films were prepared by adding the cyanated 2D conductive filler GO into the PEN matrix.The dielectric constant of PEN-GO hybrid films is significantly increased by adding only a small amount of cyanated GO.When the filler content is 0.7 wt%,the dielectric constant of the composite film without high temperature treatment is 13.20 at 1 k Hz,and that of the hybrid film after high temperature treatment is 6.32.Compared with the pure PEN film after high temperature treatment,the dielectric constant of the hybrid film is increased by up to 96.2%at 1 k Hz,and the dielectric property is relatively stable before240?,which can meet the use under high temperature conditions.In addition,the PEN-GO hybrid films still maintain the advantages of the PEN matrix in mechanical and thermal properties,and can meet the needs of practical applications.(3)The Bi₂S₃/rGO composites with one-dimensional nanorods grown on the surface of two-dimensional nanosheets were prepared by hydrothermal method.After cyanation treatment of the composites,they were added as fillers into the PEN matrix to prepare film materials.The prepared polyarylene ether nitrile-bismuth sulfide/reduced graphene oxide(PEN-Bi₂S₃/r GO)hybrid film materials have advantages in thermal properties.There is no obvious decomposition before 400?,the highest T_g of them reaches252.37?.Moreover,all of them have good mechanical properties.The dielectric properties of the PEN-Bi₂S₃/r GO hybrid films are significantly improved compared to the PEN-Bi₂S₃.The highest dielectric constant is 6.80 at 1 k Hz,which is 111.1%higher than that of the pure film after high temperature treatment.Compared with PEN-GO hybrid films,the dielectric constant of PEN-Bi₂S₃/r GO hybrid films is reduced less by high temperature treatment,and the dielectric property-frequency stability is better.The dielectric loss also decreased significantly.Similarly,the PEN-Bi₂S₃/r GO hybrid films have good dielectric properties-temperature stability which remain relatively stable before 250?.