Elastic behavior and processing of polymer melts

Abstract

Whereas the influence of viscous properties of a polymer melt on some aspects of processing has widely been reported in the literature, investigations with respect to elastic properties are rare. In this paper effects of the elastic behavior on processing and those of processing on molecular orientation and recoverable strain are presented. As elastic property the role of extrudate swell in its many facets is discussed. Experiments on cast film extrusion are described and their results discussed as a function of the Deborah number, which is often used as a quantity for the elasticity at short processing times. Film contours and resonance frequencies are presented in detail. With respect to the influence of processing on properties of manufactured items results from the literature are discussed, which show that one has to distinguish between effects on the orientation of molecule segments and on the recoverable strain. The role of non-uniform distributions of the recoverable strain within a manufactured sample for its properties is shortly addressed.Whereas the influence of viscous properties of a polymer melt on some aspects of processing has widely been reported in the literature, investigations with respect to elastic properties are rare. In this paper effects of the elastic behavior on processing and those of processing on molecular orientation and recoverable strain are presented. As elastic property the role of extrudate swell in its many facets is discussed. Experiments on cast film extrusion are described and their results discussed as a function of the Deborah number, which is often used as a quantity for the elasticity at short processing times. Film contours and resonance frequencies are presented in detail. With respect to the influence of processing on properties of manufactured items results from the literature are discussed, which show that one has to distinguish between effects on the orientation of molecule segments and on the recoverable strain. The role of non-uniform distributions of the recoverable strain within a manufactured sa...