Microstructural evolution and mechanics of hot-drawn CNT-reinforced polymeric nanofibers

To unravel reinforcing effect of CNTs in polymeric nanofibers, polyacrylonitrile (PAN)/SWNTs nanofibers with various CNTs content (0.1-0.5 wt%) were electrospun. Nanofibers were hot-drawn to enhance PAN chains and SWNT alignment. The microstructure of composite nanofibers was studied via polarized Raman and IR spectroscopy, x-ray diffraction, and TEM imaging. The study pointed to a marked contribution of SWNTs at low SWNT contents (0.1 wt%) to chain mobility and alignment during electrospinning. Evidence of volume changes was reported during hot-drawing, depending on CNT content, alluding to arrangement of CNTs in nanofibers. Indirect evidence of SWNT agglomeration, adversely affecting reinforcement efficiency at higher SWNT contents, was presented. Hot-drawing above T-g of PAN led to massive chain and SWNT alignment and orientation-induced crystallization. The most promising mechanical performance was achieved in hot-drawn ribbons with low SWNT content, where formation of an interphase-evidenced in TEM images - led to significant enhancement of effective reinforcement modulus of similar to 2.15 +/- 1.97 TPa, with the average value considerably higher than modulus of CNTs. This study demonstrates a clear path to prepare PAN nanofibers with high chain alignment as precursor for the next generation of carbon nanofibers with unprecedented strength and modulus. (C) 2016 Elsevier Ltd. All rights reserved.