Study On The General Carbon Fiber Preparation Of Liquefied Lignin

The lignin has some advantages such as high carbon content, rich rawmaterials, low-cost and so on.As a result, it is often used to prepare carbonfiber. In this study, the process parameters and the key factor to preparecarbon fiber from the base-catalyzed liquefied lignin spinning werediscussed. The main research results are as follows:(1) The spinning liquid for lignin-based carbon fiber was preparedform base-catalyzed phenol liquefied lignin, and the effects ofphenol/lignin ratio, liquefied time, binder content and polymerizationtemperatures on the carbon yield and tensile properties of the obtained fiberwere investigated. The results showed that the optimum process conditionsfor preparing the spinning solution were as follows: phenol/lignin was5:1,liquefied time was1.5h at140oC, binder content was11%, and thepolymerization temperature was140oC. Under this process conditions, Thefiber suitable for preparing of pre-oxidation carbon fiber was obtained withcarbon yield of54%at800oC.(2)In this study, the carbon fiber precursor was prepared by meltingspinning method, and we discussed the spinning speed and spinningtemperature. As a result, the best fiber spinning process parameters were asfollows: the spinning temperature is215oC, closing wire speed is450r/min.The lignin liquefaction has good spinning performance.(3) To prepare the pre-oxidized fiber, the fiber precursor, was placedin the formaldehyde/hydrochloric acid solution with the oxidizing atmosphere. Then, the pre-oxidized fiber can be obtained from thepretreatment by oxidation. The result shows that the concentration ofhydrochloric acid liquid and formaldehyde in the curing mixture was15%and18.5%, respectively; and heating rate of10oC/h and curing time of4h.The prepared fiber has good performance and is suitable for the carbonfiber preparation.(4)The best carbonization process parameters got from fiber propertyat different carbonization temperature were as follows: The carbonizationheating rate was5oC/min below300oC, and2.5oC/min after the300oC,The carbonization temperature is1000oC. The strength (the average of25single fibers) under the optimal condition was500.8MPa and the largestone can reach631MPa; the average modulus was50.5GPa and the largestone can reach87.3GPa. Finally, the study has reached a better levelcompared with the past (350-550MPa) in the field of carbon fiber.