TIME-RESOLVED X-RAY STUDY OF POLY(ARYL ETHER ETHER KETONE) CRYSTALLIZATION AND MELTING BEHAVIOR .1. CRYSTALLIZATION

Time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) experiments using synchrotron radiation were made in order to study the isothermal crystallization behaviour of poly(aryl ether ether ketone) (PEEK). Two types of long period (L(B) and L(C)M), the scattering invariant Q, and the linear degree of crystallinity within the lamellar stacks x(CL) were estimated from the Lorentz-corrected plot and the correlation function. As a result, the average lamellar thickness l(C) was calculated as the product of L(C)M and X(CL) during crystallization at temperatures of 230-310-degrees-C. The bulk degree of crystallinity (by weight), psi(C), was determined by WAXD. It was found that both long periods decreased, Q increased and I(C) remained approximately constant with time. The decrease in the long period was explained by the lamellar insertion within the lamellar stacks, whereas the increase in Q was attributed to the increase in the bulk-volume degree of crystallinity x(C), rather than X(CL). In addition, the values of the long period and of Q were found to increase with temperature as a result of the thicker lamellae. Finally, our results support the model of two populations in lamellar thickness, namely the primary lamellae which are developed first in bundle-like stacks, and the narrower, secondary lamellae (as a small fraction) that are inserted later between the primary lamellae under various spatial restrictions.