Nucleating agent induced impact fracture behavior change in PP/POE blend

This work was focused on the impact fracture behavior of polypropylene/ethylene-octene copolymer (PP/POE) blends with and without nucleating agent (NA). The crystallization morphologies of injection-molded-bar were analyzed by polarization optical microscope and the impact-fractured surface morphologies were characterized carefully through scanning electronic microscope. Our results show that the addition of 0.2 wt% alpha/or beta-NA induces the great decrease of spherulites diameters companioned with the dramatically enhancement of PP/POE blend toughness. Virgin PP shows the typical brittle-fractured characteristic during the whole fracture process. PP/POE shows the less-ductile fracture feature with multiple-craze formation. The addition of NA into PP/POE blend changes the fractured surface feature from predominantly multiple-craze to predominantly shear yielding or shear yielding involving materials cavitations and second-crack re-initiation, respectively, indicating the change from brittle-like fracture mode to ductile fracture mode. The transformation of beta -> alpha during the impact process for beta-NA nucleated samples has been observed; however, such transformation is suppressed by the presence of POE.