Fabrication Of Carbon Fiber From PBT/lignin Blends

Lignin is the second rich aromatic material only inferior to cellulose in amount. Usually lignin is a by-product of pulping process and without recycled. This thus causes big problem in environment protection and materials utilization. Therefore, to apply lignin has been long time taken as a target for scientists, especially at moment relating to the energy source problem in the world.Lignin has complicate structure and available applied as both micro-or macromolecules directly in some cases. As known, it has groups e.g. the phenyl, phenolic hydroxyl, aliphatic hydroxyl, carbonyl, carboxyl, methoxyl, conjugated double bond et al. to provide the possibility of further chemical reaction and application.Taking natural lignin and poly (butylene terephathalate), PBT, as raw materials and melt spinning method, we prepared several lignin/PBT blend fibers initially. Then these blend fibers were further oxygen treated and carbonized under different temperature conditions. The structure and properties of these carbonized fibers were characterized by FTIR spectroscopy, DSC and SEM.Before fiber fabrication, the lignin has been initially studied on its particle size, structure, morphology, thermal behavior, surface properties and dissolution behavior in acid and base solutions, respectively.To blend lignin with PBT with different weight ratios by using a DACA microcompounder and characterized by FT-IR spectroscopy, different scanning calorimetry (DSC) and scanning electronic microscopy (SEM). DSC curves indicated that these blends have good miscibility and the reason described by FTIR spectra seems to be due to lignin rich in hydroxyl groups and caused strong intermolecular hydrogen-bonding with PBT structure. Additionally, this was also observed by SEM photographs.The better blend fibers were chosen to convert to carbon fiber by oxygen treatment and final carbonization under two different temperatures and related increasing rates, respectively.Based on FTIR spectra of those obtained carbon fibers, the structure is obviously contributed by lignin relating to the C=C and OH groups located at 1660 and 3420 cm"1, respectively, suggesting the PBTcomponents might be removed in carbonization.The SEM photographs of carbon fiber showed that this case we prepared carbon fiber is of interest and unlike the traditional fiber we observed generally since no visible morphology. However, the fiber observed is exactly and seeming to be the same as electrospinning method yielded fiber because the fibers we observed in SEM figures have a diameter of about 1.25-0.25μm, and length about 180μm. Moreover, both these sizes are found to be varied in relation to the carbonization condition. However, the further investigation on understanding the mechanism for these fine fiber formation is still required.