Enhancement of imidization of poly(amic acid) through forming poly(amic acid)/organoclay nanocomposites

Abstract

The imidization kinetics of nanocomposites of poly(amic acid) and organoclay were analyzed with in situ Fourier Transform Infrared spectra at several temperatures. The poly(amic acid) studied consisted of pyromellitic dianhydride and 4,4'-oxydianiline. It was found that by dispersing a small amount of organoclay in nanometer scale in the poly(amic acid), both the imidization temperature and the imidization time of the poly(amic acid) can be reduced dramatically. In specific, when two parts of exfoliated silicate layers of organoclay was dispersed in the poly(amic acid), the imidization temperature was lowered by 50 degrees C (250 degrees C versus 300 degrees C) for achieving a complete imidization. Additionally, the imidization time of the poly(amic acid) at 250 degrees C can be reduced to 15 min when the amount of organoclay increased to seven parts. Using a first-order reaction to model the imidization kinetics of poly(amic acid)/organoclay, a 20% drop in the activation energy for imidization of PMDA-ODA/organoclay (7 phr) was obtained as compared to that for imidization of neat PMDA-ODA. (C) 1999 Elsevier Science Ltd. All rights reserved.