PURE COMPONENT PROPERTIES AND MIXING BEHAVIOR IN POLYOLEFIN BLENDS

This paper summarizes an extensive investigation of the thermodynamic interactions that govern phase behavior in blends of polyolefins and e xamines their relationship to pure component PVT properties. Interacti on strengths, obtained by small-angle neutron scattering (SANS) measur ements, were classified as regular or irregular according to their con sistency with a solubility parameter formalism. Characteristic pressur e P and temperature T* were obtained from PVT data on the pure compon ents with various liquid-state models. For the regular blends, a close correspondence was found between the SANS-based and PVT-based solubil ity parameter assignments, the latter being closely related to P, as expected. The pattern of deviations for the irregular blends, positive in some and negative in others, effectively ruled out equation-of-sta te contributions as a general explanation. However, the results sugges t that mismatches in both P and T* play some role, and we offer some tentative attempts at generalization.