Investigation of polyimide-mica hybrid films for cryogenic applications

A series of polyimide-mica hybrid films that consist of PMDA-ODA and mica were prepared by the solution ultrasonic dispersion technique, and characterized by XRD, UV-Vis transmission, cryogenic mechanical testing, dynamic mechanical analysis (DMA) and SEM. The effects of mica content and temperature on the cryogenic mechanical properties, dynamic mechanical properties, glass transition temperatures (Tg) and morphologies of fracture surface were discussed. It was observed that the strength and stiffness of the hybrid films could be simultaneously increased when the mica content was lower than 10 wt%, and the tensile strength and modulus of the hybrid films at cryogenic temperature (77 K) were obviously higher than those at room temperature. Compared with pristine PI film, the hybrid films with 1-5 wt% mica contents would be more possibly used as advanced cryogenic materials in superconductive cable and magnet systems.