Relation between carbonization behavior of polycarbodiimide films and stabilization conditions

In the process of produce carbon materials by pyrolyzing polycarbodiimide ( PCDI), the starting PCDI is preliminarily stabilized by a low temperature t reatment in an oxidative atmosphere. In this study, the relation between th e carbonization behavior of PCDI films and the stabilization conditions was investigated with the aim of optimizing stabilization conditions. The exte nt of stabilization was evaluated from the changes in tensile modulus durin g stabilization and density. A two stage stabilization was proposed to obta in sufficient thermal stability without causing fusion of the films. From t he viewpoint of minimizing weight loss and volume reduction and maintaining the shape of the starting material during carbonization, PCDI films requir ed a stabilization giving densities in the region from ca 1.22 to 1.26 g cm (-3). During carbonization, a large weight loss took place at ca 480 degree s C, and the decomposition at this temperature favored the crystallite grow th at higher carbonization temperatures. Thus, with increasing density of t he stabilized him beyond 1.26 g cm(-3), more intensive decomposition took p lace, and the crystallite size and the density of the carbonized films incr eased although the weight loss increased. (C) 1998 Elsevier Science Ltd. Al l rights reserved.