Effect of heat treatment on the thermal and mechanical properties of a precursor polymer: polyhydroxyamide

The film type precursor polymer showed excellent thermal stability as determined using TGA under nitrogen. Endothermic enthalpy peaks were observed at 319-351 degrees C for various annealing temperatures from DSC thermograms. It was unusual to observe such large heat capacities, from 221.1 to 131.7 J/g, which decrease with increasing annealing times and temperatures. The Values of the tensile strength and initial tensile modulus of the precursor films were enhanced remarkably with increasing annealing temperature. The values of the tensile properties increased almost linearly with increasing annealing time at 250 and 350 degrees C. But for films annealed at 450 degrees C, the Value of the tensile strength significantly increased from 137 to 332 MPa, but remained constant with increasing annealing time. Similar results were observed for the initial modulus. For determining the biaxial stress of the film in the precursor state, holographic interferometry was used to identify the resonant modes of vibration. The precursor polymer showed limited solubility in common solvents, but showed good solubility in DMAC and NMP with LiCl when heated above 80 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserved.