Design and Control of Close Proximity Indirect Exposure for Nonthermal Atmospheric Pressure Plasma-Based Oxidation of Carbon Fiber Precursor

A new plasma-based method for the stabilization of polyacrylonitrile carbon fiber precursor utilizing reactive chemical species derived from a custom atmospheric pressure plasma generation system was developed and demonstrated. As opposed to the conventional stabilization method of convective heating in air, plasma-based stabilization efficiently introduces oxidative reactive species that both diffuse through and react faster with the precursor filaments, resulting in a faster and more efficient process. This method was successfully demonstrated with a variety of precursor chemistries, grades and sizes. The development effort was entirely experimental, with successive processing devices designed and constructed to examine various aspects of the process and to scale the technique to ever-greater throughput. The technology was scaled from the benchtop level to the small pilot line scale of 1 annual metric tons of throughput. The author was directly responsible for inventing a new plasma processing method, developing the theory behind it, designing and implementing the plasma generation system, and integrating it with the experimental processing equipment. Compared to conventional oxidation, plasma oxidation has demonstrated a 2.5-3X reduction in processing time with a 75% reduction in unit energy savings, all while meeting or exceeding the final fiber properties from conventional processing.