Bio-renewable fibers extracted from lignin/polylactide (PLA) blend

Abstract

Due to the high cost and environment issues in the production of carbon fiber from polyacrylonitrile (PAN) and pitch, the use of low cost bio-renewable materials are of great interest as an alternative precursor. Lignin is a highly aromatic biopolymer, extracted as a byproduct of wood pulping and has been investigated as a suitable precursor for carbon fibers. In the present work, we have demonstrated the feasibility of spinning modified lignin/polylactide (PLA) blend into robust, fine lignin fibers. Chemical modification of raw lignin via butyration was investigated to enhance the miscibility of lignin with PLA due to the formation of ester functional groups in place of highly polar hydroxyl (-OH) groups. The butyrated structure was confirmed by nuclear magnetic resonance (NMR) spectroscopy and fourier transform infrared spectroscopy (FTIR). Modified lignin /PLA blends at different compositions were prepared by melt mixing in a twin-screw micro compounder. The influence of the blend composition on the compatibility between lignin and PLA was examined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Thermogravimetric analysis (TGA) results of different blends revealed a systematic enhancement in the stability of the blends with the increase in PLA content from 0 to 50 wt .%. Lignin fibers were measured to possess modulus of about 500 to 2500 MPa, varied by B-lignin and PLA composition. Cylindrical morphology was observed in all lignin fibers. After carbonization, microvoids structure could be seen in ligninbased carbon fibers. Carbon fibers from B-lignin/PLA 75/25 maintained fibrous structure while carbon fibers from other ratios deformed during carbonization.