At present,with the development of the energy field,the requirements for capacitors continue to in-crease.Capacitors with high temperature performance and high energy storage have become a research hotspot.High energy storage density requires high dielectric constant and low dielectric loss.The special engineering mate-rial polyimide(PI)is favored by people because of its high temperature resistance,but its low energy storage density restricts its application.In order to make better use of the high temperature resistance of polyimide and find an ex-cellent synthesis route from the diversity of its synthetic raw materials,this paper aimed to prepare polyimide(PI)with high dielectric constant and low dielectric loss,and study the effect of isomer 2,3,3',4'-biphenyltetracarboxylic dianhydride(a-BPDA)and 3,3',4,4'-biphenyltetracarboxylic dianhydride(s-BPDA)on the dielectric properties of polyimide.Using a-BPDA,s-BPDA,3,3',4,4'-benzophenonetetracarboxylic dianhydride(BTDA),4'-bis(3-amino-phenoxy)diphenyl sulfone(m-BAPS)as raw material,PI film was prepared by ternary copolymerization,so as to verify the feasibility of the scheme.On this basis,the proportion of raw materials was allocated to explore the best performance of various raw material ratios.The films were characterized by FTIR analysis,XRD analysis,thermal per-formance analysis and dielectric performance analysis.The experimental results show that a-BPDA,s-BPDA,BTDA and m-BAPS can successfully synthesize polyimide films.The synthesized films still have high thermal properties.a-BPDA and s-BPDA increase the glass transition temperature of polyimide to 245.8℃and 239.1℃,respectively.s-BPDA and a-BPDA have different effects on the dielectric properties of polyimide.When the ratio of s-BPDA to BTDA is 3∶2,the dielectric constant of sPI was 4.25 and the dielectric loss is 0.002 9 at 1 000 Hz.When the ratio of a-BPDA to BTDA is 3∶2,the dielectric constant of aPI is 3.49 and the dielectric loss is 0.002 3.Under comprehensive comparison,s-BPDA is more effective in improving the thermal and dielectric properties of polyimide.
polyimidetri-component copolymerizationhigh dielectric constantlow dielectric lost
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