Relationship between fiber structure and carbonized temperatures of carbon fiber from wood tar

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Carbon fiber, initially developed for aerospace use, has attracted great interest since the 1960s. Although the main precursors of carbon fiber such as viscose rayon, coal tar pitch and polyacrylonitrile usually afford high-performance materials, it is necessary to develop cheaper and environmentally advantageous sources such as biomass. In this work, we found that the biomass carbons prepared at 800℃ and 2000℃from wood tar had high electric conductivity by measurement of the volume resistivity.(1) Autoclave reaction : The autoclave reaction was carried out for 30 min under reduced pressure at 200-500 ℃ to give wood tar pitch in 20%- 60% yields. The temperature was gradually raised by programmed heating at 2℃/min and then kept for 30 min at the final temperature.(2) High temperature treatment of wood tar pitch : The wood tar pitch was put into a quartz pipe and then heated at 800℃ with a heating speed of 2℃/min under nitrogen. After 1 h, the pitch fiber was cooled to r.t, and the structure of the product was analyzed by X-ray.(3) Film coating : the high temperature treated pitch was smashed to powder until the diameter of the particle was around 10 to 30 μm. The powder was mixed with a solution of PVDF in NMP (12%), followed by coating on PET film using film applicator with micrometer. Then the film was dried in the oven at 130℃ for 10 min.(4) Electric conductivity measurement : The electric conductivity of the biomass carbon film was investigated by means of electric resistivity measurement. The volume and surface resistivity of the obtained film was measured by using low resistivity meter, suggesting that the biomass carbon films had high electric conductivity.