Combined effects of stretching and nanofillers on the crystalline structure and mechanical properties of polypropylene and single-walled carbon nanotube composite fibers

The combined effects of stretching and single-walled carbon nanotubes (SWCNTs) on crystalline structure and mechanical properties were systematically investigated in melt-spun polypropylene (PP) fibers prepared at two different draw ratios. The dispersion, alignment of the SWCNT bundles and interfacial crystalline structure in the composite fibers are significantly influenced by the stretching force during the melt spinning. The nanohybrid shish kebab (NHSK) superstructure where extended PP chains and aligned SWCNT bundle as hybrid shish and PP lamellae as kebab has been successfully obtained in the composite fibers prepared at the high draw ratio and the related formation mechanism is discussed based on the results of morphological observations and 2d-SAXS patterns. Large improvement in tensile strength and modulus has been realized at the high draw ratio due to the enhanced orientation and dispersion of SWCNT bundles as well as the formation of NHSK.