UNIAXIAL DRAW OF POLY(ETHER ETHER KETONE)/POLY(ETHER IMIDE) BLENDS BY SOLID-STATE COEXTRUSION

Amorphous and crystalline blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) have been drawn uniaxially by solid-state coextrusion over the whole composition range. The amorphous blends have been drawn at 125 degrees C which is below the T(g)s of these compatible blends, and the crystalline blends have been drawn at 125 degrees C and also at 225 degrees C, which is above the single T-g. Reported are the effect of draw on T-g, PEEK crystallization, and the respective orientations of PEEK and PEI in the drawn blends. The T(g)s of the miscible amorphous PEEK/PEI blends are depressed up to 6 degrees C by draw, but their densities are slightly increased, contrary to conventional free volume theory. The density of the crystalline PEEK drawn at 125 degrees C exhibits a minimum at an extrusion draw ratio (EDR) of about 2.0, whereas that of the crystalline PEEK drawn at 225 degrees C increases monotonically with EDR. The densities of the crystalline blends drawn at both 125 and 225 degrees C decrease monotonically with EDR. These observations are attributable to the interplay between the destruction of the lower-melting PEEK crystals and the increasing packing in the amorphous regions on drawing. The effect of draw on the crystallization kinetics of PEEK and in PEEK/PEI blends has been evaluated by DSC. PEEK in the drawn blends crystallizes faster on cold crystallization. On the other hand, when the samples were annealed in the melt followed by crystallization (melt crystallization), the drawn PEEK crystallizes slower than the undrawn PEEK. The orientations of PEEK and PEI in the amorphous drawn blends were studied by infrared dichroism. It is found that the orientations of both PEEK and PEI at a given draw ratio increase with increasing PEEK content in the blends.