Experimental observations on the pressure-dependent polymer melt rheology of linear low density polyethylene, using a multi-pass rheometer

Abstract

We report experimental data for a linear low density grade of polyethylene at elevated temperatures using a newly designed Multi-Pass Rheometer. This rheometer is capable of measuring oscillatory viscoelastic data and steady shear capillary measurements on the same test fluid within an enclosed environment. Data presented in this paper show that at low pressures there is reasonable self-consistency between the Multi-Pass data and separate oscillatory data obtained by using a Rheometrics Mechanical Spectrometer and steady shear data obtained from a Rosand capillary rheometer. In addition, we report experimental data on the pressure dependence for both viscoelastic and steady shear data over the range of 1–230 bar. The steady shear results appear to be consistent with previously published data. The apparent viscosity and the viscoelastic data both show a linear increase of about 20% over the pressure range tested.