Thermal properties of a thermoplastic polyimide blend

Differential scanning calorimetry and dynamic mechanical analysis of blends of a new thermoplastic polyimide (TPI) and poly(ether imide) (PEI) have co nfirmed the full miscibility of the system over the whole composition range . Annealing of the blends above the glass transition temperature of TPI, bu t below its crystallization temperature, did not produce a shift in the gla ss transition, while physical ageing of the annealed blends also failed to reveal any indication of phase separation. The rate of crystallization of T PI was slowed by the addition of PEI, and the temperature of the maximum cr ystallization rate shifted upwards. The beta-relaxation behavior of the ble nds followed a linear trend between the response of the component polymers, while the low-temperature gamma-relaxation was unchanged by blending. The time scale of physical ageing of the blends did not behave in a linear fash ion, and the enthalpy loss on ageing also deviated from the average. (C) 19 99 John Wiley & Sons, Inc.