Crystallizability in a Model High-Performance Thermoplastic Polyimide-Matrix Composite

Abstract

The effect of annealing and exposure to high temperatures on the crystallizability and glass transition of a model thermoplastic polyimide/carbon fiber (TPI/CF) system was investigated in this work. A varying range of crystallinity was obtained by annealing the TPI/CF prepreg at different temperatures. The relaxation of the material was observed when the prepreg was annealed at temperatures above the glass transition. On the other hand, exposure to high temperatures close to the processing temperature irreversibly affected the material, and the material lost the ability to crystallize (permanent structural changes). The loss of crystallizability was observed after the exposed materials were annealed. This loss of crystallizability was paralleled with an increase in the Tg. Both relaxation and permanent structural change effects are higher for greater times and higher temperatures. In conclusion, the response of TPI/CF to treatment at temperatures higher than the glass transition temperature was characterized in this work. The loss in crystallizability and changes in glass transition temperature were observed, which will be essential for further investigations on process modeling and performance.

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