The Society of Rheology: 69th Annual Meeting (Oct 1997) Abstract of Paper

Session	Rheology and Mixing
Date	Tuesday, October 21, 1997
Time	4:25
Room	Senate

Paper Title and Authors

Title	VISCOSITY MODEL FOR POLYDISPERSE POLYMERS
Authors	D. Nichetti and I. Manas-Zloczower
Address	Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH 44106, USA

Authors' Information

Name	E-mail
Nichetti, Dario	dxn8@po.cwru.edu
Manas-Zloczower, Ica	ixm@po.cwru.edu

Abstract

The rheological behavior of polymer melts is profoundly influenced by the molecular weight and molecular weight distribution. It is well recognized that the relationship between viscosity and shear rate is sensitive to the polydispersity and they play a critical role in the polymer processability. We have developed a theoretical model relating the flow behavior of a polymer melt to its molecular weight distribution. The non-Newtonian behavior of a polymer melt is considered to be the consequence of gradual transition of high molecular weight fractions to the rubbery state. For a monodisperse polymer the flow behavior remains Newtonian up to the critical shear stress . At shear stress in excess to the critical value, the polymer shows a shear-thinning behavior. We assume the critical shear stress, to depend on the chain length for each polymer homologous series. This model provides a master curve, which gives realistic predictions of flow behavior for monodisperse systems. The model has been also extended to predict flow behavior for systems with broader molecular weight distribution. When a logarithmic-normal distribution function was used to characterize molecular weight distribution, we found an analytical solution for the relationship between shear viscosity, polydispersity index and weight average molecular weight. Our model has been applied to develop single screw extruder characteristic curves for polymers with the same weight average molecular weight but different polydispersity. We found a linear relationship between the flow rate and the polydispersity index.

Developed by Albert Co, The Society of Rheology
Please e-mail suggestions and comments to albertco@umecheme.maine.edu.
Application Version: September 1997

69th Annual Meeting (Oct 1997)

Abstract of Paper MX3

Paper Title and Authors

Authors' Information

Abstract