STUDY ON THE STRUCTURE AND MISCIBILITY OF PBPI-E PTI-E BLENDS/

The crystallization, miscibility and structure of polyimide PBPI-E/PTI -E blends were studied by DSC, DMA, NMR and fluorescence techniques, w here PBPI-E is a biphenyldianhydride-based polyimide, and PTI-E is a p olyimide from 4,4'-thiodiphthalic anhydride and 4,4'-oxydianiline. The results obtained show that PBPI-E/PTI-E blends are miscible at a mole cular level for all the compositions studied. However, the glass trans ition temperature of the blends is well below the value predicted by t he Fox equation, and the blends are not stable at high temperature, i. e. phase separation will occur when the blends are annealed about T-g. Moreover, the melting point T-m, differential enthalpy Delta H and sp in-lattice relaxation time T-l(c) of the blends increase with the anne aling time. (C) 1997 Elsevier Science Ltd. All rights reserved.