Fabrication and mechanical, electrical properties study of polyimide films curing at low-temperature condition assisted by microwave

Polyimide (PI) films with excellent mechanical and electrical properties were produced at a low temperature assisted by microwave. Depending on the reciprocating movement of dipole molecules excited by microwave, even though under a low temperature, the rotation and conformational changes of functional groups could also be promoted. Thus, reaction between N-H bond and -OH in carboxyl which could realize dehydration and cyclization of polyamic acid proceeded normally. Results revealed that the combination between ambient temperature only at 70 degrees C and microwave power at 2000 W or higher could also produce PI films with imidization degree of 100%. For PI-2000W, compared with traditional PI film (PI-300 degrees C) that generated only at temperature of 300 degrees C, even though on the basis of no any change in molecular structure and addition of filler, the tensile strength, elastic modulus, crystallinity, and apparent density increased by about 21%, 51%, 37%, and 5%, respectively. For electrical properties, conductivity enhanced by one to two orders of magnitude comparing with PI-300 degrees C. Results indicated that while keeping the original molecular structure of PI films unchanged, this work provided a new and effective method to assist the enhancement in mechanical and electrical properties of PI films.