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Shear-induced crystallization of polypropylene: influence of molecular structure

✍ Scribed by Duplay, Catherine; Monasse, Bernard; Haudin, Jean-Marc; Costa, Jean-Louis

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
292 KB
Volume
48
Category
Article
ISSN
0959-8103

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✦ Synopsis

The isothermal crystallization of isotactic polypropylenes has been studied under static conditions and under shear ýow. The shear was induced by displacement of a glass übre in the molten polymer. An a-monoclinic crystalline phase was formed with a columnar organization at the surface of the glass übre, which did not appear under static conditions. The growth rate, constant during shear-induced crystallization experiments, is compared with the results obtained from static crystallizations. An important increase of the growth rate due to the shear ýow is observed. This increase depends on the molecular weight and the tacticity of the polypropylene. Actually, the molecular weight and the isotactic index seem to be the most important molecular parameters. Their augmentation leads to a signiücant increase of the growth rate, which can be increased by a factor of seven, under the present conditions.

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