REINFORCEMENT EFFECT AND MOLECULAR MOTIONS IN SEMICRYSTALLINE PEEK FILMS - MECHANICAL AND PHYSICAL MODELINGS .1.

The influence of the crystalline phase on the viscoelastic behavior of poly (aryl ether ether ketone) (PEEK) films is assessed by dynamic me chanical spectrometry. Prediction of the viscoelastic behavior near T- g of semicrystalline films is performed through mechanical and physica l modelings. Changes in the ct relaxation induced by the crystalline p hase are related to both the mechanical coupling between phases and th e decrease in the molecular mobility of chains, which is improved for samples showing a broad crystallite size distribution. Crystalline pha se also induces some modifications in the characteristics of the beta spectrum. The reinforcement effect brought by the crystalline phase in such a temperature range is predicted through a mechanical model. The n, changes in tan delta level in the beta(1) region induced by the cry stalline phase result from the mechanical coupling between phases. The magnitude of such changes only depends on the crystallinity ratio and it is not controlled by the crystallite size distribution. The crysta lline phase also induces changes in the pattern of the beta(2) transit ion, which could be attributed to modifications in the conformations o f the chains near the crystalline entities and/or the magnitude of int eractions between chains. Such modifications seem to be sensitive to t he thermal history of PEEK samples. (C) 1997 John Wiley & Sons, Inc.