MORPHOLOGY OF QUENCHED AND ANNEALED ISOTACTIC POLYPROPYLENE.

Abstract

Transmission electron microscopy of permanganate-etched surfaces of isotactic polypropylene (i-PP) that has been quenched from the melt into ice water shows equi-axed 'lump' crystals of ca. 20 nm across, in contrast to a well-developed lamellar morphology of melt-crystallized samples. Annealing the quenched i-PP up to 140 degree C does not lead to any significant changes in this 'lump' crystal morphology, whereas the broad peaks in wide-angle X-ray diffraction (WAXD) patterns of the quenched i-PP change to the sharp crystal patterns of alpha -form above ca. 80 degree C and approach those of melt-crystallized samples upon annealing above 120 degree C. Only upon melting a substantial amount of original crystals above 140 degree C, the crystal morphology begins to exhibit lamellar-like features and the crystal size determined from the electron micrographs shows a substantial increase.