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Article: Stress relaxation in low-shrink-force polyolefin films.
- Article from:
- Polymer Engineering and Science
- Article date:
- September 1, 2004
- Author:
CopyrightCOPYRIGHT 2004 Society of Plastics Engineers, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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INTRODUCTION
Polyolefin shrink films are widely used in the packaging industry. In recent years they have been replacing PVC (polyvinyl chloride) films, which degrade with HCl formation, and which are sometimes not approved for food contact. One well-known process for producing polyolefin shrink films is called the "double-bubble" process. In this process the extruded polymer tube is quenched with water in order to prevent formation of large crystallites, reheated below the polymer melting temperature, and then inflated with compressed air. By this method, orientation in both machine (MD) and transverse (TD) directions takes place almost simultaneously. Therefore ...