SEMICRYSTALLINE MORPHOLOGY OF POLY(ARYL ETHER ETHER KETONE) POLY(ETHER IMIDE) BLENDS

A variety of semicrystalline morphologies in poly(aryl ether ether ketone)/poly(ether imide) (or PEEK/PEI) blends are revealed by electron and optical microscopy. Although the two polymeric components are compatible in the melt, phase separation occurs during crystallization of the PEEK component. At high temperatures (approximately 320-degrees-C), compact PEEK spherulites are observed even for dilute blends containing only 25% PEEK, and the accumulation of rejected PEI is primarily interspherulitic. At intermediate temperatures, PEI segregates primarily to pockets between bundles of lamellae within a spherulite. The length scale of segregation is progressively smaller at lower temperatures. At the lowest temperatures, approximately 35-degrees-C above the glass transition temperature, a new and unexpected single-crystal-like dendritic morphology results. This morphology appears unique to the blends and consists of short, crystallographically faceted lamellae, uncharacteristic of typical PEEK lamellae. At all temperatures, the same unit-cell dimensions for PEEK are found.