Kinetic Model of Polyacrylonitrile Fibre Thermostabilisation in Nitrogen Atmosphere
The article proposes a modification of the method of polyacrylonitrile bundle thermal stabilization in the production of carbon fiber. The use of an additional processing stage in a nitrogen medium at the initial stage will allow to make a separation of the ongoing processes of cyclization and dehydrogenation, which will make it possible to increase the reaction rate and the carbon performance of the fiber. For this purpose, the commercially produced polyacrylonitrile fiber was stabilized at various temperatures and exposure times, followed by measurement of the volume density of the samples. Based on the data on the time change in the density of polyacrylonitrile fiber samples during processing in nitrogen, the degree of transformation of the initial linear structures of polyacrylonitrile into cyclized ones was estimated. Based on the obtained data, a kinetic model of the process with the determination of the reaction order, the rate constant and the activation energy is constructed. The use of such an additional stage will allow to achieve the required volume density values to obtain a stabilized fiber capable of undergoing high-temperature processing (carbonation) more quickly and, accordingly, increase the productivity of the equipment, which will lead to a reduction in the cost of producing medium-strength carbon fibers in future .