Studies of injection-moulded isotactic poly(propylene) by synchrotron WAXD/SAXS: Effects of nucleating agent on morphological distribution

The morphological distribution of injection-moulded isotactie poly(propylene) (iPP) plates in the presence of nucleating agents was extensively investigated using synchrotron radiation. The commercial PP compound was injection-moulded under a variety of different conditions in order to e plore the effects of shear flow and temperature on the morphology and morphological distribution. The iPP structures obtained were characterized using the degree of crystallinity, alpha-phase orientation index, beta-phase index, long spacing of lamellae, and the thickness of both crystalline and amorphous lamellae. These parameters were plotted as a function of position through the plate depth for the injection-moulding conditions. Unlike relatively pure iPP, the distributions of crystallinity and alpha-phase oientation index in this commercial iPP are independent of position through the plate depth. The skin-core structure that is generally found for injection-moulded iPP is not present because of the addition of nucleating agents. The beta-phase of iPPhas the same distribution through the plate depth as that expected for iPP without mucleating agents. Additionally, the lamellar dimension is found to be independent of position through the plate depth and the fraction of noncrystalline materials residing outside the lamellar stacks can be up to about 30%. The results indicate that the properties of different injection-moulded iPP grades should be investigated individually. [GRAPHS] Typical WAXS patterns of the sample S9 at different labeled distances from the surface. The patterns are vertically shifted for clarity.