Effect of Folding in Large-Tow Polyacrylonitrile Fibers on Microstructure and Properties of Pre-oxidation Fibers

Abstract

The state consistency of polyacrylonitrile (PAN) precursor fibers significantly impacts the stability of carbon fiber performance. In this paper, the impacts of folding during boxed storage on the microstructure and mechanical properties of large-tow PAN fibers and pre-oxidation fibers (OXFs) were explored. It was found that folding can damage the surface of PAN fibers, giving rise to defects like cracks and extrusions. Moreover, it leads to the loosening of the internal microfibril arrangement, the enlargement of pore sizes, and the decrease of microcrystalline orientation within the fibers. These structural alterations are inherited by OXFs, which not only disadvantage the pre-oxidation process but also result in the deterioration of mechanical properties. This research offers valuable reference data for the selection and optimization of precursor fiber storage methods prior to entering the pre-oxidation oven in the industrial production of large-tow PAN-based carbon fibers.