Preparation and characterization of wet spun fibers based on TPU/PVDF/CNT

Wet spinning is a process in which the polymer–solvent solution is extruded through spinneret orifices into a coagulation bath. Upon contact with the bath medium, phase inversion occurs due to solvent–nonsolvent exchange, the solvent diffuses out of the polymer structure, and the solidification of the filament begins. Thermoplastic polyurethane (TPU) is a flexible and biocompatible polymer with high resistance to abrasion, tensile stress, and chemicals. Poly (vinylidene fluoride) (PVDF), due to its favorable mechanical strength, high thermal/chemical stability, and non-toxicity, is widely used, while multi-walled carbon nanotubes (MWCNTs) are employed to enhance the strength of composite fibers. In this study, the wet spinning process parameters for fabricating TPU, TPU/PVDF, and TPU/PVDF/MWCNT monofilaments were investigated. In general, increasing the polymer content in the spinning dope increased the fiber diameter, tensile strength, and elongation at break. The addition of PVDF, due to the increase in viscosity, led to larger fiber diameters; however, because of the inherently inelastic nature of PVDF, the tensile strength and initial modulus increased, while the elongation of fibers decreased. The incorporation of MWCNTs resulted in increased fiber modulus owing to the reinforcing effect of MWCNTs.