Liquid-liquid phase separation in linear low density polyethylene-solvent systems

In this contribution the results of an investigation on the influence of pressure, solvent type and polymer structure on liquid - liquid phase separation in LLDPE - solvent systems is reported. Lower solution temperatures (LST) in LLDPE + solvent systems were determined experimentally as a function of pressure at 400-600 K and at pressures up to 13 MPa. The solvent type and the presence of ethylene in the LLDPE - solvent mixture appear to be the most important factors that govern the solubility of LLDPE, while the structure of the LLDPE itself is of minor importance. It is shown that the Perturbed Hard Chain Theory predicts a priori the right type of phase behaviour. Moreover the experimental trends in solubility with changing solvent type and molecular weight of the polymer are equally well predicted.