Characterization of pitches by an ultrasonic method - Change in the molecular aggregation state during air-blowing

The air blowing reaction has been used to modify the chemical structure and molecular aggregation of pitches for general-purpose carbon fiber on an in dustrial scale. The purpose in this study is to obtain fundamental ultrason ic data so that one can monitor in situ the change in chemical structure an d molecular aggregation state in air blowing reaction. For this purpose, th e effects of heat-treatment, oxygen (or air), and distillation (or low pres sure) on the ultrasonic properties were separately examined. It was found t hat the ultrasonic measurements give the temperature dispersion curve chara cteristic to the structure, which was quite consistent to previous studies by ESR and NMR. (C) 2001 Elsevier Science Ltd. All rights reserved.