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Article: Aging characteristics of oriented poly(ethylene terephthalate).
- Article from:
- Polymer Engineering and Science
- Article date:
- July 1, 1995
- Author:
CopyrightCOPYRIGHT 1995 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
Physical aging behavior, ie the gradual relaxation of polymer chains, is usually observed for polymers in their glassy state. Aging of several amorphous and semi-crystalline glassy polymers has been studied by various authors and has been the subject of reviews, papers, and books. Polymeric materials, when quenched to temperatures below their glass transition temperature, [T.sub.g], do not attain thermodynamic equilibrium. These materials can be referred to as super cooled liquids having excess free volume and excess enthalpy. The term excess is with reference to the equilibrium state. The non-equilibrium nature of the glassy state results in ...