Mechanical & Materials Engineering, Department of

 

Date of this Version

2010

Comments

Published in Synchrotron Radiation in Polymer Science (SRPS 4) IOP Conf. Series: Materials Science and Engineering 14 (2010) 012005; doi:10.1088/1757-899X/14/1/012005 Copyright 2010 IOP Publishing Ltd. Used by permission.

Abstract

Shishes are fibrillar crystallites that can be created by deforming a polymer melt. The formation of shishes takes place when flow is strong enough to stretch molecules. In the early stages, bundles of stretched molecules with pre-crystalline order form metastable precursors whose stability depends on their size and, hence, on the stress level. We find that for a specific isotactic polypropylene, close to the nominal melting point, a stress larger than 0.10 MPa leads to stable fibrillar precursors that are partially crystalline immediately after flow. On the other hand, below 0.10 MPa, the aspect ratio of precursors tends to unity and the lack of crystallinity makes these structures prone to dissolution.