BROADENING OF THE GLASS-TRANSITION IN BLENDS OF POLY(ARYL ETHER KETONES) AND A POLY(ETHER IMIDE) AS STUDIED BY THERMALLY STIMULATED CURRENTS

Blends of poly (aryl ether ketones) (PAEKs) and an amorphous poly (eth er imide) (PEI) were used as model systems to study the broadening of the glass transition due to crystallization and the resulting depletio n of PAEK from the amorphous phase. Two different PAEKs were studied, which are completely miscible with PEI in the amorphous state; poly (a ryl ether ether ketone) (PEEK) and a slower crystallizing poly (aryl e ther ketone ketone) (PEKK). Relatively rapid crystallization condition s were chosen in order to trap a significant fraction of PEI between t he PAEK crystal lamellae or between bundles of lamellae. The broad gla ss transitions are apparently a result of the nonuniform nature of thi s process. The breadth of the glass transition was quantified by therm ally stimulated currents (TSC) applied in the thermal sampling (TS) mo de. The results compared favorably with DSC data. The magnitude of the apparent activation energy obtained by the TS method allows one to as sign the relaxations as cooperative (glass-transition-like) or non-coo perative and to define the limits of the glass transition with a highe r degree of precision than other techniques. Cooperative relaxations c an be resolved with this technique, even if they are only a small frac tion of the overall relaxing species at a given temperature. In some c ases the glass transition region was found to broaden to ca. 60-degree s-C after crystallization.