Effect of β nucleating agent on mechanical properties of PP/POE blends

Polypropylene/polyolefin elastomer (PP/POE) blends with and without β nucleating agent were prepared by injection moulding. Wide angle X-ray diffraction (WAXD) results are in agreement with differential scanning calorimetric (DSC) melting curves; both demonstrate the formation of the hexagonal β phase after adding β nucleating agent in PP/POE blends. The addition of β nucleating agent increases the toughness of PP and PP/POE blends but decreases their tensile strength. Brittle–ductile transition (BDT) occurs in PP/POE blends, but no obvious BDT point can be seen in β nucleated PP/POE blends. The toughening mechanism, morphology of the fractured surfaces after impact, was investigated by scanning electron microscope (SEM). From impact strength interparticle distance curves, a critical interparticle distance of ∼0·2 μm is seen in PP/POE blends, but no critical value is observed for β nucleated system, indicating better interaction between PP and POE, deduced by their good compatibility. The toughening and softening effect of β nucleating agent is also responsible.