Preparation of functionalized partially unzipped carbon nanotube/polyimide composite fibers with increased mechanical and thermal properties

Partially unzipped carbon nanotubes (PUCNTs) were prepared via a facile longitudinal unzipping method and then covalently bonded with 4,4',4"-triaminotriphenylamine (TAPA) for the first time to obtain functionalized PUCNTs (f-PUCNTs). Polyamide acid (PAA)-based composites with f-PUCNTs were prepared by using in situ polymerization, and the f-PUCNTs/PAA composite solution was wet-spun to obtain composite fibers which were finally transferred into f-PUCNTs/PI composite fibers after heat treatment. f-PUCNTs not only combined the advantages of carbon nanotubes and graphene, but also possessed groups which could covalently bond with the PI matrix, leading to a relatively strong reinforcing effect on the matrix. The tensile strength and Young's modulus of the composite fiber containing 1.0 wt% f-PUCNTs increased to 165% and 208% relative to those of PI fiber, respectively, and to 137% and 153% relative to those of the composite fiber containing the same amount of PUCNTs, respectively. Meanwhile, the thermal properties also increased obviously, e.g. the 5% weight loss temperature and glass transition temperature of the composite fiber containing 1.0 wt% f-PUCNTs were 50 degrees C and 13 degrees C higher than those of PI fiber, respectively.