Study On The Preparation Of Carbon Fiber By Lignin Melt Spinning

Lignin is the highest aromatic polymer in plants and a by-product of the use of cellulose.The direct emissions not only cause environmental pollution,also a waste of resources.In recent years,industrial lignin was processed into dispersant,water reducer of cement,reducing viscosity of drilling fluid agent and other low-value products,but less high application.Industrial lignin is cheap,renewable biodegradable,and high carbon content.If it is used to prepare carbon materials,the advantages are both the cost of carbon materials and the use of lignin value.The structure and thermal stability of industrial lignin were characterized by infrared and thermogravimetry.The results showed that the extraction process of six industrial lignin did not destroy the original skeleton structure of lignin.The thermal stability of the kraft lignin(KL)and alkali lignin lignin(AL-2)was better than others.The solubility of industrial lignin was investigated.The results showed that there was no suitable solvent for purifying pine ligninsulfonates.The highest yield of Alkaline lignin(AL-1)was only 20%.KL and AL-2 were purified by acidic aqueous solution and the yield was over 95%.Therefore,KL and AL-2 with high purification efficiency were selected for further study on the preparation of carbon fiber.The lignin was characterized by Py-GC/MS and HAKEE rheometer.The results showed that the lignin was mainly composed of guaiac wood lignin derivatives,and the modified lignin was phenol derivatives.The viscosity of modified lignin was sensitive to temperature,and under the same test condition,the viscosity is mainly determined by the proportion of low molecular weight and the molecular weight of raw lignin.The melt spinning and melt blowing of lignin were simulated by rheometer.The spinnability temperature of modified lignin and the optimum melt-blown temperature of modified KL were obtained.The results showed that the diameter of lignin-based fibers prepared by melt-blown method was smaller than that of melt-spinning.The best technological parameters of fiber curing,preoxidation and carbonization were determined by thermal and elemental analysis.Finaly,carbon fiber felt with carbon content of 95.15%was prepared.