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 (LB and L~), the scattering invariant Q, and the linear degree of crystallinity within the lamellar stacks XCL were estimated from the Lorentz-corrected plot and the correlation function. As a result, the average lamellar thickness Ic was calculated as the product of L~c and XCL during crystallization at temperatures of 230-310°C. The bulk degree of crystallinity (by weight), ~kc, was determined by WAXD. It was found that both long periods decreased, Q increased and lc 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 Xc, rather than XCL, 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.
Посилання на статтю:
Time-resolved X-ray study of poly(aryl ether ether ketone) crystallization and melting behaviour: 1. Crystallization / Benjamin S. Hsiao, KennCorwin H. Gardner and Dan Q. Wu // Polymer. – 1993. – Vol 34. – P. 3986-3995.
