Crystallization, orientation, and mechanical properties of laser-heated photothermally drawn polypropylene/multi-walled carbon nanotube fibers

Polypropylene (PP)/multi-walled carbon nanotube (MWCNT) fibers at MWCNT contents of 0, 0.5 and 1 wt% were melt spun and photothermally drawn by irradiating them with a near-infrared laser during elongation. These fibers were then compared to hot-drawn PP/MWCNT fibers. The crystallinity of the photothermally drawn PP/MWCNT fibers was higher, whereas the degree of orientation of PP crystals was similar for both types of fibers. However, the degree of orientation of MWCNTs in the photothermally drawn PP/MWCNT fibers was higher, which was ascribed to the laser-induced local heating effect of MWCNTs dispersed in the polymer matrices. Higher breaking stress and modulus were obtained for the photothermally drawn PP/MWCNT fibers at the same MWCNT content. Therefore, laser-induced photothermal drawing has significant potential as a fiber-drawing method for enhancing the mechanical properties of the PP/MWCNT fibers.