Polypropylene / (Ethylene-Propylene) Copolymer Blends. Surface Morphology and Elasticity as Measured by AFM and FMM

Quantitative and qualitative methods were developed to measure the surface mechanical properties of polymers by atomic force microscopies. They were used to study the effects of molding processes and of viscosity on the surface morphology of polypropylene / (ethylene-propylene) copolymer blends (PP/EP). On compression-molded "physical blends", EP nodules are present at the outermost surface while, on injection-molded "reactor blends", they are covered by a PP layer. Resins with high viscosity ratio between EP and PP present heterogeneous surface elastic properties corresponding to the dispersion of spherical EP nodules below the surface. The low viscosity ratio resins have homogeneous surface elastic properties comparable to those measured above EP nodules on high viscosity ratio resins. This is compatible with a fine dispersion of plate-like shaped EP nodules below the surface