Rheological Studies of Dynamically Vulcanized and Mechanical Blends of Polypropylene and Ethylene-Propylene Rubber

Abstract

Abstract An experimental study is presented of the rheological properties of (i) polypropylene, (ii) a commercial polypropylene/ethylene-propylene terpolymer a dynamically vulcanized blend (PP/EDPM-TPE) and (iii) a mechanical blend of a polypropylene and an ethylene-propylene copolymer. The polypropylene behaves as a typical flexible chain thermoplastic exhibiting a zero shear viscosity and higher shear rate non-Newtonian viscosity, well defined normal stresses, an elongational viscosity three times the zero shear viscosity, and an equality of the shear viscosity and the complex viscosity (Cox-Merz Rule). The PP/EPM-TPE exhibits an apparent yield value in shear flow, unmeasurable normal stresses and a complex viscosity which is much greater than the shear viscosity. This is behavior similar to that of particle filled compounds, block copolymers and liquid crystalline thermoplastics and suggests a material with a rest state structure. The behavior of the PP/EPM mechanical blend is intermediate.