ON SURFACE-MORPHOLOGY AND DRAWING OF POLYPROPYLENE FILMS

Citation
Rh. Olley et Dc. Bassett, ON SURFACE-MORPHOLOGY AND DRAWING OF POLYPROPYLENE FILMS, Journal of macromolecular science. Physics, B33(2), 1994, pp. 209-227
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Polymer Sciences
ISSN journal
0022-2348
Volume
B33
Issue
2
Year of publication
1994
Pages
209 - 227
Database
ISI
SICI code
0022-2348(1994)B33:2<209:OSADOP>2.0.ZU;2-I
Abstract
Two nominally equivalent grades of polypropylene designed for similar applications were extruded into sheets, with one surface chilled rapid ly, giving a smooth texture; and the other being rougher, with a struc ture of spherulites separated by crevices formed by retraction of the last traces of molten polymer. Differences in the two grades gave rise to differences in spherulitic morphology, in terms of both spatial di stribution of spherulites among die lines and the proportions of alpha - and beta-spherulites. The sheets were subjected to three kinds of de formation: unrestricted monoaxial, restricted monoaxial (plane strain) , and biaxial. The effects of surface variations persisted right throu gh the drawing process. The morphology of the rough surface in particu lar was observed (a) to dominate the process of deformation, especiall y necking as it initiated at surface crevices between spherulites; and (b) to affect the optical quality of the final product, most signific antly in the structure and number of haze rings. Legacies of beta-sphe rulites in fully drawn films can be observed at all levels, from the u naided eye down to lamellar structures observed in the transmission el ectron microscope.