Comparing Two Electrospinning Methods in Producing Polyacrylonitrile Nanofibrous Tubular Structures with Enhanced Properties

Abstract

Polyacrylonitrile nanofibrous tubular structures were produced through typical and opposite charge electrospinning methods and the effect of the method as well as the two key electrospinning parameters, namely concentration of the electrospinning polymer solution and rotational speed of mandrel collector on properties of such tubular structures were studied. The smples were characterized by X-ray diffraction, scanning electron microscopy, Fast Fourier Transform method and tensile tests. Increasing polymer solution concentration considerably increased the diameter of the nanofibers and decreased the bead formation, where the increasing ranges of the average diameters were larger and sizes of beads were smaller for the nanofibers produced by the opposite charge set-up. Nanofibers' diameter, on the other hand, decreased as the speed of the rotational mandrel increased and the observed decline was greater in the opposite charge method, especially at higher concentrations of polymer solution. An inversion point for the anisotropy of mechanical properties was found to be around 2164 rpm. The aspect ratio of the nanofibers also increased with increasing the take-up speed. Increasing the take-up speed increased the mechanical force of pulling the jet, resulting nanofibers with smaller diameter, which in turn improved the crystallinity and molecular orientation of the fibers that explained the enhanced tensile properties for smaller diameter fibers. Different breaking mechanisms for the randomly oriented fibers and directionally aligned nanofibers were observed.