In-situ fabrication of polyimide microphase and its effects on the mechanical and dielectric properties of polytetrafluoroethylene composite films

Due to the ultralow surface energy of polytetrafluoroethylene (PTFE), PTFE composites usually exhibit poor interfacial interaction and mechanical performances. Herein, a water-soluble precursor of polyimide (PI) was added into the PTFE aqueous emulsion, and well-distributed PI microphase was in-situ constructed in PTFE matrix through the thermal imidization of the precursor during the sintering process of PTFE. The welldistributed PI microphase resulted in significant improvements in the tensile strength, stiffness, and creepresistance of PTFE. Compared with pure PTFE, the tensile strength and Young's modulus of PTFE/PI (5 wt%) film increased by 28.1% and 122.3%, and the creep strain decreased by 42.4%. Meanwhile, the film maintained high elongation at break (308.4%), low dielectric constant and loss (2.09 and 0.0014 @10 GHz), exhibiting great potential in the field of high-frequency communication.