Fluorinated Al2O3/siloxane modified PI films towards vastly enhanced corona resistance performance

Polyimide (PI) films with excellent corona-resistant performance are vital in multitudinous electrical equipment. Here we employ a largely unexplored strategy to effectively restrain phase separation behavior of siloxane modified PI through chain extension copolymerization (PI-e-Si), thereby generating dense SiO2-like storage space under corona that shows powerful ability of encircling and restraining electron/ion, which restricts their direct and persistent attack for PI segment. Therefore, PI-e-Si film owns obviously longer corona-resistant lifetime (30.8 min) than that of pristine PI film (6.4 min) based on accelerated corona-aged test. Furthermore, fluorinated Al2O3 (F-Al2O3) with strong corona-resistant ability is applied to construct a solid barrier for dense SiO2-like storage space, which synergistically strengthens restraint effect for electron/ion, and it also optimizes heat-conducting and dielectric properties of PI film. Finally, fabricated composite film (PI-e-Si/F-Al2O3) further improves corona-resistant lifetime up to 66.8 min, superior to that of Kapton 100 CR film (a famous corona-resistant PI film).