Rheological models for unified curves for simplified design calculations in polymer processing

Abstract

A method has been proposed earlier by Shenoy et al. to estimate complete flow curves depicting the variation of melt viscosity over industrially relevant range of shear rate and temperature through the use of unified curves characteristic of each generic type of polymer. In the present paper, the unified curves have been fitted through modified forms of already known generalized Newtonian models. The advantage of fitting such rheological models to unified curves lies in the fact that calculations involving entrance length estimates, heat transfer, die design, mold design, etc. are greatly simplified. Knowing the model parameters, one needs to know only the melt flow index, which is a relatively easy parameter to obtain, to make any engineering design calculations. The modified generalized Newtonian models have been fitted to a number of polymers covering one or more from each group of olefinics, styrenics, cellulosics, vinyls and engineering thermoplastics.