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Micronecking in thin films of isotactic polypropylene
Author(s) -
Plummer Christopher John George,
Kausch HansHenning
Publication year - 1996
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1996.021970621
Subject(s) - spherulite (polymer physics) , tacticity , materials science , composite material , lamellar structure , crystallization , deformation (meteorology) , polypropylene , transmission electron microscopy , ultimate tensile strength , polymer chemistry , polymer , chemical engineering , polymerization , nanotechnology , engineering
Thin melt crystallized spherulitic films of isotactic polypropylene have been deformed in uniaxial tension at different temperatures and examined by transmission electron microscopy. As the temperature was increased above approximately −80°C, a transition from high aspect ratio craze‐like features to highly voided shear deformation zones was observed, these latter initiating both at spherulite boundaries and along the spherulite diameters perpendicular to the tensile axis. In rapidly crystallized films, the draw ratio in the deformation zones was estimated to be close to the natural draw ratio of the melt entanglement network, and was independent of test temperature in the range investigated. However, for crystallization temperatures above approximately 125°C, the mean draw ratio within the deformation zones was found to increase with crystallization temperature. It was also observed that, although the draw ratios in deformation zones in ß spherulites were similar to those in α spherulites in films containing both modifications, the former showed more homogeneous textures. This suggests that the particularly pronounced textures associated with α spherulites in polypropylene thin films are linked to their crosshatched lath‐like lamellar morphology.