Preparation, Configuration And Properties Characterization Of Carbon Fiber From Liquefied Bamboo

Carbon fiber can be made by PAN fiber or pitch fiber via oxidation, low-temperature carbonization, high-temperature carbonization process. The process used by PAN fiber is simpler and mechanical properties of carbon fibers are better. However, the shortage of fossil resource caused precursors of PAN fiber to become fewer and fewer in recent years, which caused the cost rise of carbon fibers, so the material development for carbon fibers has been one of important study fields. The research on bamboo liquefication in recent years, base on which it can be used as replaced material for materials of carbon fiber.In this Paper, the reproducible bamboo was used to be material, the optimized preparation process and carbonization process of precursors were studied detailedly by orthogonal tests; The configuration, change of chemical groups during precursor preparation and weight loss process were studied and analyzed by SEM, XRD, FTIR and TGA etc.; The change rule of interior configuration, micro-crystal structure, specific surface area, porous structure, electricity properties during carbonization was studied by SEM, XRD, Laser Raman Spectrometry, mercury indicator, Electronic Tensile Tester for Single Fiber, FTIR, TG-MS and SEM-EDAX etc., based on which the following conclusions were obtained.1) The optimized preparation process of precursors:Spinning velocity is 800r/min, synthetic temperature is 120℃, synthetic agent content is 5%, temperature-rising time is 30min:Phosphoric acid chroma is 18.5%, temperature-rising speed is 5℃/h, stabilizing temperature is 85℃and stabilizing time is 2h. Based on which the precursors could be prepared, its average diameter is 28μm, average tensile strength is 148.26MPa, average tensile modulus is34.68GPa, average breaking elongation is 1.62%.2) After bamboo was liquefied to liquefied bamboo, its crystal became lower. When the liquefied bamboo became spinning solution, its crystal became higher. The crystal became higher after the spinning solution was changed into precursors.The precursor surface was smooth, it had smooth cross-sections, and its border is more compact than the center, many fine pores were mainly observed around the center of the cross-section of carbon fibers. Some precursor s had skin-core structure, and there were distortions and nodes in Partial precursor s.3) The cellulose, hemi-cellulose and lignin in bamboo combined with phenol during bamboo liquefication, which could produce more aryl-ramifications.During the course of precursor preparation, firstly, synthetic agent combined with phenol to make new hydroxymethyl, simultaneously, Partial hydroxymethyl reacted with each other or Partial hydroxymethyl reacted with alive hydrogen on aromatic ring to form (-CH2O-) and methylene bridges respectively. Then With the rising of temperature, Partial hydroxyketone reacted with each other to form original fibers. Finally, the aromatic ring of original fibers reacted with +CH2OH simultaneously, Partial (-CH2O-) and hydroxymethyl transformed to methylene, more hydroxyketone reacted with each other or more hydroxyketone reacted with+CH2OH to form (-CH2O-), thus netty structure precursors formed primarily.4) The optimization process of precursor carbonization:fiber diameter is 24μm, temperature-rising speed is 2℃/min, carbonization temperature is 1000℃, temperature-keeping time is 80min, based on which the better carbon fiber from liquefied bamboo can be prepared, its average tensile strength is 982.60MPa, average tensile modulus is 98.76GPa, average breaking elongation is 4.98%, average yield ration is 55.68%.5) The surface of carbon fibers from liquefied bamboo was more smooth, there were no obvious disfigurements; They had ellipse cross-sections and its border is more compact than the center. Many fine pores were mainly observed around the center of the cross-section of carbon fibers. It also had skin-core structure, moreover, some carbon fibers could form hollow fibers during carbonization.6) Between 300℃and 1000℃, carbon fibers from liquefied bamboo belonged to graphite-like amorphous carbon structure. With the rising of carbonization temperature, the content of carbon element increased, its specific pore volume and specific surface appeared increasing tendency; However, the content of oxygen element decreased, its average porous diameter became smaller and smaller, its resistivity decreased gradually, and its graphite-like crystal structure became regular and orderly. At the same carbonization temperature, with the increasing of carbonization time, the content of carbon element increased gradually, the content of oxygen element appeared decreasing tendency, its resistivity decreased gradually, moreover, its resistivity decreased accompanied with the lower of crystal structure Parameters(La,Lc,d002)7) Below 300℃, the rate of weight loss of precursor was 5.07%, pyrolysates of precursors included CO, CO2, phenol and CH2O; Between 300℃and 600℃, its rate of weight loss reached 41.20%, pyrolysates of precursors included CO, CO2, CH4, benzene, methylbenzene, phenol, methylphenol,2-methylphenol and Partial polymers; Between 600℃and 1000℃, the rate of weight loss was only 3.33%, the precursors were decomposed to CO2 and methylbenzene.