Gel-spun carbon nanotubes/polyacrylonitrile composite fibers. Part II: Stabilization reaction kinetics and effect of gas environment

Gel-spun polyacrylonitrile (PAN) and carbon nanotube (CNT) composite fibers have been stabilized using various processing conditions to study the kinetics of stabilization reactions. Differential scanning calorimetry, infrared spectroscopy, wide angle X-ray diffraction and thermo-gravimetric analysis studies suggest that individual stabilization reactions can be separated at different stabilization stages when inert and oxidative environments are used in sequence. Among various stabilization reactions, it was found that the cross-linking has the highest activation energy, followed by cyclization and oxidation. The oxidation preferentially occurs with the cyclized structure and the shrinkage during stabilization is affected by the gaseous environment. The addition of CNTs reduces both entropic and reaction shrinkages, and improves the maximum tension that a fiber can bear during stabilization in both inert and oxidative environments.