Carbon nanofibers prepared by a novel co-extrusion and melt-spinning of phenol formaldehyde-based core/sheath polymer blends

A novel route based on the solvent-free core/sheath melt-spinning of polypropylene/(phenol formaldehyde–polyethylene) [PP/(PF–PE)] to prepare the carbon nanofiber (CNF) has been demonstrated in this study. The approach consists of three main steps: co-extrusion of PP (core) and a polymer blend of PF and PE (sheath), followed by melt-spinning, to form the core/sheath fiber, stabilization of core/sheath fiber to form the carbon fiber precursor, and carbonization of carbon fiber precursor to form the final CNF. Both scanning electron microscopy and transmission electron microscopy images reveal long and winding CNF with diameter 100–600 nm and length greater than 80 μm. With a yield of ~45% based on its raw material PF, the CNF exhibits regularly oriented bundles which curl up to become rolls of wavy long fibers with clean and smooth surface. Results from X-ray diffractometry, Raman spectroscopy, and selected area electron diffraction pattern further reveal that the CNF exhibits a mixed-phase carbon material with graphitic particles embedded homogeneously in an amorphous carbon matrix.