Thermal characterization of the glass transition of heterocyclic polymer networks

Heterocyclic polymer networks obtained by copolymerization of an epoxy olig omer and hexamethylene diisocyanate (HMDI) in different proportions have be en studied by differential scanning calorimetry (DSC) in their glass transi tion regions. The glass transition temperature and the specific heat capaci ty increment at the transition correlate well with sample composition, wher eas the index of the distribution of relaxation times seems to be unaffecte d by composition changes. The structural relaxation process is characterize d with an equation for the configurational entropy, whose material paramete rs are determined by a fit to a wide class of thermal histories. (C) 1999 E lsevier Science B.V. All rights reserved.