RHEOLOGICAL STUDIES OF DYNAMICALLY VULCANIZED AND MECHANICAL BLENDS OF POLYPROPYLENE AND ETHYLENE-PROPYLENE RUBBER

An experimental study is presented of the rheological properties of(i) polypropylene,(ii) a commercial polypropylene/ethylene-propylene terp olymer a dynamically vulcanized blend (PP/EDPM-TPE) and (iii) a mechan ical blend of a polypropylene and an ethylene-propylene copolymer. The polypropylene behaves as a typical flexible chain thermoplastic exhib iting a zero shear viscosity and higher shear rate non-Newtonian visco sity, well defined normal stresses, an elongational viscosity three ti mes the zero shear viscosity, and an equality of the shear viscosity a nd the complex viscosity (Cox-Merz Rule). The PP/EPDM-TPE exhibits an apparent yield value in shear flow, unmeasurable normal stresses and a complex viscosity which is much greater than the shear viscosity. Thi s is behavior similar to that of particle tilled compounds, block copo lymers and liquid crystalline thermoplastics and suggests a material w ith a rest state structure. The behavior of the PP/EPM mechanical blen d is intermediate.