TIT# Melting and Crystallization of Differently Oriented Sets of Crystallites
     in Hard-Elastic Polypropylene
AUT# Stribeck, Norbert; N”chel, Ulrich; Funari, S‚rgio S.;
SOU# Macromolecules (2009), ~, submitted Nov 11 2008
LOC# xv119
CLA#
COM#
APP#
MAT#
ABS# Uniaxially oriented polypropylene (PP) is molten and crystallized
     isothermally from the oriented, quiescent melt. Nucleation and growth of
     differently oriented sets of crystallites (c-set and a*-set) appear
     decoupled. After shallow quench crystallization is preceded by (spinodal)
     decomposition. Evolution is monitored by wide-angle X-ray scattering
     (WAXS) and compared to results of a SAXS study.
     Peak integrals (crystallinity) and crystallite size are tracked. In the
     commercial starting material a*-set crystallites melt at 158øC. The
     c-set melts at 170øC furnace temperature. After recrystallization both s
     ets melt at 170øC. Isothermal crystallization is divided in two distinct
     phases. During nucleation the crystallinity stays low. The second phase
     is dominated by crystallinity growth. At 150øC the c-set is seeded first.
     At 145øC and 140øC a*-oriented crystallites are the first. The
     first-seeded set starts to grow first. c-set crystallinity is always
     growing faster than a*-set crystallinity. The evolution of the SAXS
     cross-diagram in the growth phase can both be explained by lamellae
     growing at right angles, and by block merging.