Toughness of β-nucleated Isotactic Polypropylene

摘要

The mechanism of improvement in toughness in β-iPP was studied on the basis of the fracture and plastic deformation mechanism of iPP. The toughness of β-iPP modified with a proper quantity of N, N'-dicyclohexyl-2, 6-naphthalene dicarboxamide, as a β-crystal nucleating agent (0.05-0.15 wt%) was improved in comparison with that of α-iPP. Although both the strength of craze and yield stress of β-iPP, which are characteristic values for fracture, were lower than those of α-iPP, the increase of the ratio of craze strength to yield stress resulted in the improvement of toughness of β-iPP. Furthermore, it was confirmed that the high density of microcraze contributes to the improvement of toughness of β-iPP because of the release of plastic constraint.