Influence of the Phase Morphology on the Viscoelastic Behaviour of Polymer Blends

Melts of polyethylene-propylene-rubber (EPR, blens of linear polyethylene, linear polyprpylene, and PE-PP copolymer) show phase separation. The influence of the phase morphology on the viscoelastic behaviour is studied with the aid of the dynamical moduli. The measured moduli of the fractionof the linear homopolymer of an EPR agree with the moduli calculated from the molar mass distribution of this fraction. In contrast, the copolymer fraction shows a strong rubber-like behaviour. Mixtures of 80 wt% linear PP and of EPRs with low copolymer content are not rubber-like liquids. In addition, the moduli from them can be calculated from the moduli of the components with the aid of Paliern´s emulsion model. This clearly reveasl that the linear PP forms the matrix in this case. Mixtures of 80 wt% linear PP and of EPR´s with high copolymer content show rubber-like behaviour and Pallierne´s emulsion model is not applicable on them. Obviously, the copolymer fraction forms a physical network.