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 pha se separation in LLDPE - solvent systems is reported. Lower solution t emperatures (LST) in LLDPE + solvent systems were determined experimen tally 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 - sol vent mixture appear to be the most important factors that govern the s olubility of LLDPE, while the structure of the LLDPE itself is of mino r importance. It is shown that the Perturbed Hard Chain Theory predict s a priori the right type of phase behaviour. Moreover the experimenta l trends in solubility with changing solvent type and molecular weight of the polymer are equally well predicted.