Effect of Heating Rate on the Chemical Reaction during Stabilization of Polyacrylonitrile Fibers

The influence of the heating rate on the stabilization process of polyacrylonitrile (PAN) fibers was studied. The results show that with an increase in heating rate, the density and oxygen content show a continuous decrease. As a result, the strength continues to increase and the skin-core structure becomes more evident. However, the amount of shrinkage and the conversion index ( A _I ) are lowest at 5°C/min. On the basis of these observations, we conclude that at a heating rate lower than 5°C/min the intramolecular cyclization is the main reaction and its extent decreases with an increase in heating rate. Above 5°C/min, an intermolecular cross-linking reaction becomes more obvious and increases with an increase in heating rate.