Melt-Processing and Properties of Coaxial Fibers Incorporating Carbon Nanotubes

Polypropylene-multiwalled carbon nanotube (PP-CNT) composites were spun into fibers using melt-spinning methods. The CNT content was varied by diluting the commercial masterbatch with a low viscosity PP homopolymer grade. The conductivity, as well as the mechanical properties, of the fibers were systematically tested in order to find the optimal formulation. Post-stretching was used to improve the mechanical properties of the fibers as well as to decrease the fiber diameters. Fibers having a conductivity of 0.4 S/cm, a Young's modulus of 5.4 GPa and a tensile strength of 250 MPa were obtained after a three-fold stretching. Trilayer coaxial fibers similar to data transfer coaxial cables (two conductive layers separated by an insulating layer) were then produced in a one-step melt-spinning method using a specially designed die, followed by solid state post-stretching.