Synthesis And Characterization Of Thermo-crosslinking And End-capped Polyimide

Aromatic polyimides(PI)possess the good thermal stability,electrical,radiation resistance and mechanical property,due to the rigidity of their backbone.With the rapid development of smart grids and high-speed trains,the higher requirement was put forward for the ability of anti-voltage insulation.The polyimide coating thickness needs to be improved in order to meet the requirement.However,the polyimide is not soluble in common solvent.What’s worse,the polyamic acid concentration is less than 20%,which is not suitable for the thick film.Besides,it is important to improve the concentration of polyamic acid while reduce the viscosity of the solution.The right viscosity is matched with semiconductor process.To ensure the low viscosity and high solid content,synthesis of the low molecular weight of polyamide acid was focused by utilizing end-capping agent.After the thermal imidization and crosslinking reaction,the high molecular weight polyimide coating film was formed.The high molecular weight is essential for the high insulating properties and thermal stability.The details are listed as:(1)The high solid content of PAA(by terminated with MA)was synthesized by two-steps.Then analyzed the factors such as the solid content,the structure of main chain and the content of MA that may affect the the PAAs viscosity,the film-forming properties and the properties of PI films.The crosslinking PI films have excellent overall performance.(2)The high solid content of PAA(based on ODAP,BPDA and BTDA)was prepared by terminated with NA.After the thermal imidization and crosslinking reaction,the high molecular weight polyimide coating film was formed.Study the kinds of dianhydride and the content of NA influence on the PAAs viscosity,the film-forming properties and the properties of PI films.The crosslinking PI films possess the excellent thermal stability,electrical insulating performance and good mechanical properties.(3)At last,we studied the PAAs(based on ODA-6FDA)end-capped by MA or NA and the crosslinking PI films properties;the kinds of dianhydride and the content of 4-PEPA influence on the PAAs viscosity,the film-forming properties and the properties of PI films were investigated.The result showed that the crosslinking PI films still have the excellent thermal stability,electrical insulating performance and good mechanical properties.