THE EFFECT OF BACKBONE STRUCTURE ON THE CLOUD POINT BEHAVIOR OF POLYETHYLENE ETHANE AND POLYETHYLENE PROPANE MIXTURES

Cloud-point data to 155-degrees-C and 1300 bar are presented for mixtures of propane and ethane with polyethylene fractionated with respect to molecular weight and degree of chain branching. As the number of chain branches in the backbone of the polyethylene increases, the heat of fusion decreases and the pressure needed to obtain a single phase decreases by approximately 140 bar in ethane and approximately 70 bar in propane. The cloud-point curves for the unfractionated parent polyethylene in either solvent is at higher pressures than those for the fractionated samples, suggesting that high molecular weight oligomers and a broad polydispersity mask the effect of chain structure on the phase behaviour.