AGGREGATION AND MICROSTRUCTURE OF ETHYLENE-PROPYLENE COPOLYMER VISCOSITY IMPROVING ADDITIVE

Static light scattering measurements of ethylene-propylene random copo lymer revealed that solvophobic ethylene segments were responsible for both aggregation and cluster density variations over temperature. By changing the molar ratio of ethylene to propylene, as well as the solv ent, we controlled the degree of solvophobicity. This caused markedly different combinations of aggregation and density variations with temp erature. Combinations observed from 50 to -10 degrees C included: a) c onstant aggregation and density for an E/P ratio of 60/40 in methylcyc lohexane, b) increased aggregation at -10 degrees C combined with a co nstant cluster density for an E/P ratio of 60/40 in tetralin and an E/ P ratio of 80/20 in methylcyclohexane, c) increased aggregation and de nsity at -10 degrees C for an E/P ratio of 80/20 in tetralin. We also show how these combined microstructural changes are related to intrins ic viscosity measurements made from 50 to -10 degrees C in these same solvents.