High pressure phase equilibria in the system linear low density polyethylene+ethylene: experimental results and modelling

Abstract

Cloud point isopleths were measured for a binary system of linear low density polyethylene (LLDPE) and ethylene. Cloud points were determined at temperatures between 395 and 440 K and pressures up to 175 MPa. The LLDPE used was made from hydrogenated polybutadiene and was almost monodisperse ( M w/ M n=1.08). The experimental data were modelled with the Sanchez–Lacombe equation of state. The parameters for LLDPE were found by performing a sequence of non-linear regressions on both the experimental cloud-point data and pressure–volume–temperature reference data for molten polyethylene. The Sanchez–Lacombe equation fits the data well, although not within the experimental uncertainty.