Twisted of Polyacrylonitrile /Lignin Nanoyarns for Enhanced Alignment and Rapid Stabilization

Abstract

Polyacrylonitrile (PAN) and PAN/lignin precursor fibers were fabricated using both conventional and modified electrospinning setups. The modified setup was designed to produce uniaxially aligned nanoyarns, applied in-situ tension and twisting to improve fiber alignment and reduce diameter. Twisted PAN fibers exhibited the best alignment and smallest diameter (~50 µm), while PAN mats showed broader alignment distribution with ~75 µm diameter. PAN/lignin nanoyarns had a larger average diameter (~150 µm) but retained good orientation. All twisted fibers were subjected to stabilization by varying temperatures and heating rates to evaluate their structural and chemical changes. Characterization using Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were analyzed to study the effects of different stabilization parameters. FTIR analysis revealed that lignin enhanced cyclization and oxidation at higher temperatures, indicated by a reduction in C≡N and C–H, and increase in C=N groups. At high temperature of 260˚C and at 10 ˚C/min temperature rate has reduced the stabilization duration tremendously by 60% without jeopardizing structures formation during stabilization process. These results highlight the effectiveness of the modified electrospinning setup and the potential of PAN/lignin nanoyarns for the subsequent carbonization stages as a greener and sustainable carbon fiber precursors, by improving the orientation and reducing the stabilization duration.