CONSIDERATIONS OF THE FREEZING-IN OF FLOW-INDUCED ORIENTATION IN POLYMER MELTS BY VITRIFICATION WITH APPLICATION TO PROCESSING

We develop the implications of the experimentally tested hypothesis that (i) birefringence developed during flow is quantitatively frozen-in during vitrification of glass-forming polymer melts and (ii) that the rheo-optical law may be combined with a knowledge of the stress field existing immediately prior to vitrification to yield birefringence distributions. This hypothesis is applied to various problems including multiaxial stretching of sheets, melt spinning, tubular film extrusion and injection molding. Special problems concerned with internal temperature distributions are discussed. We examine difficulties which may arise in application of the hypothesis due to residual thermal stresses. Comparisons are made to other methods of representing orientation development during flow. © 1979.