Structure and properties of blends of isotactic polypropylene with ethylene-propylene oil

The structure of blends of isotactic polypropylene with ethylene-propylene oil was studied by light and atomic force microscopy, X-ray diffraction, and DSC. It was shown that the blends are heterogeneous systems which contain semicrystalline PP and oil crystallizing at low temperatures. An increase in the oil content leads to a change in the spherulite size; a decrease in the lamella size; and, accordingly, to a drop in the melting temperature of PP. The PP-oil blends are thermodynamically compatible in melt. The mechanism of PP deformation gradually varies from the ductile to the quasi-brittle mode with a significant deterioration of mechanical characteristics of the material with an increase in the oil content. The experimental results are described satisfactorily by a model of deformation of the polymer matrix alone.