Solution viscosities of ethylene–propylene copolymers in oils



Viscosities were obtained on oil solutions of ethylene-propylene copolymers with 58-80 mol% ethylene. For amorphous copolymers, intrinsic viscosities and equivalent hydrodynamic volumes showed little variation from −10 to 50°C. They decreased precipitously at low temperature for a partially crystalline copolymer with 80 mol% ethylene. The data can be explained by postulating that more ethylene and resulting crystallinity lead to ordered domains in solution at low temperatures, giving rise to additional contraction of the copolymer above that expected for a totally amorphous material.