Comparison of rheological behavior of LDPE in linear and nonlinear viscoelastic flow and using Multimode Pom-Pom model for prediction of uniaxial elongational flow

Polymer melts show complex response under the act of deformation. This response has direct relation to their molecular structure. The purpose of this study was to investigate the rheological behavior of branched polymers and the effect of branching on linear and nonlinear viscoelastic flow for usage in various industrial applications.

 Research Approach:

For this purpose, the tests such as frequency sweep and extensional for two polyethylene (LDPE) with long branches have been used. From these tests we obtained storage and loss moduli, complex viscosity and extensional viscosity. Molecular models in nonlinear regions can also be used in this regard.

Linear tests can partly show the presence of branch in LDPE, while nonlinear tests show strain hardening behavior for branched sample. One of the models for branched polymers is the Multimode Pom-Pom (MPP) model which can be used to predict the strain hardening phenomenon in extensional flows. In this study, the average number of lateral branches was also calculated using this model.