Eur. Phys. J. E 6, 305-314 (2001)
The mechanisms of recrystallization after melting in syndiotactic polypropylene and isotactic polystyrene
M. Al-Hussein and G. StroblFakultät für Physik, Albert-Ludwigs-Universität, Hermann-Herder-Str. 3, 79104 Freiburg, Germany alhussei@uni-freiburg.de
(Received 23 July 2001 and Received in final form 4 October 2001)
Abstract
Several semicrystalline polymers show a recrystallization after melting during a
heating scan. We have studied the mechanisms of such recrystallization processes for two
different polymers, namely syndiotactic polypropylene (sPP) and isotactic polystyrene (iPS). This
was done by monitoring the structure evolution during the recrystallization process and its
changes during a subsequent heating scan via time- and temperature-dependent SAXS measurements,
respectively. The results of this study showed that the sPP samples exhibited a recrystallization
mechanism similar to the multi-stage route found upon initial crystallization of semicrystalline
polymers from an entangled melt. Meanwhile, a different recrystallization mechanism was shown by
the iPS samples. In this case, the recrystallization process proceeded as a direct growth into
the melt in a one-step process. This is the first time we have observed such a mechanism which
resembles the picture presented by the classical models for crystallization from an entangled
polymer melt. The reason for such different mechanisms may be related to the initial melt state
prior to crystallization. It seems as though, when crystallization sets in an entangled polymer
melt, it follows the multi-stage route, whereas if the melt is locally disentangled, it proceeds
by a direct growth mechanism.
61.41.+e - Polymers, elastomers, and plastics.
64.70.-p - Specific phase transitions.
64.60.My - Metastable phases.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
