Structural effects of compatibilizer localization and effectivity in thermoplastic polyurethane–polyolefin blends

A study was performed with blends of thermoplastic polyurethanes and polyolefins to determine the structural requirements for a compatibilizer to be located at the interface. It was demonstrated that during the addition of an incompatible polymeric additive (i.e., incompatible with both blend constituents) to a polyurethane–polyolefin blend, the additive migrated to the interface. This interfacial phenomenon was proven to be virtually independent of compatibilizer viscosity or surface activity. Only when the compatibilizer was quite comparable to one of the phases did small differences in polarity govern whether the compatibilizer remained at the interface or formed micelles. This effect was demonstrated with a series of styrene–(ethylene–butylene)–styrene block copolymer compatibilizers.