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Sheared isotactic polypropylene (iPP) forms a special crystalline assembly called branched shish kebab. The effects of two colorants, Cu-phthalocyanine and ultramarine blue, on the branched shish-kebab structure have been investigated by using synchrotron wide-angle x-ray scattering. The effects of the colorants on the morphological distributions of iPP are well constructed through the shear field or temperature gradient, including crystallinity, molecular orientation, fraction of lamellae, and thickness of crystalline lamellae. It is found that the Cu-phthalocyanine can significantly affect the morphological development of sheared iPP but the ultramarine blue cannot. In the presence of Cu-phthalocyanine, the degree of crystallinity is increased, the molecular orientation is enhanced, the more a*-axis-oriented components form, and the crystalline lamellae are thickened. [ABSTRACT FROM AUTHOR]

The molecular and lamellar orientations of injection-moulded isotactic polypropylene were investigated using simultaneous wide- and small-angle X-ray scatterings. In order to obtain the meaningful degree of molecular orientation with respect to the flow direction, the axis orientations of parent and daughter lamellae were separately calculated. The molecular orientation of thin material is consistent with the lamellar orientation. However, the decrease in the lamellar orientation of thick material is associated with a constant degree of molecular orientation, which would indicate an intra slip between parent lamellae along the flow direction. [ABSTRACT FROM AUTHOR]

Abstract: Small-angle X-ray scattering (SAXS) studies were carried out to investigate effects of sodium benzoate (SB) on the shear-induced distributions of lamellar structures through the depth direction of injection-moulded isotactic polypropylene (iPP) plates, using the micro beam available from a synchrotron to gain good spatial resolution. It was found that in the presence of SB, the shish–kebab structure emerges over a broader range to include regions in which a random arrangement of crystalline lamellae is found without SB. The oriented crystalline lamellae are even found in positions that are very close to the core center. The SB-induced shish–kebab structure under low levels of shear flow is attributed to lower free energy barriers for the coil-to-stretch transition and shorter times to start the crystallization. The effect of SB on the lamellar dimensions is significant only in the core region, and only when the concentration of SB is sufficiently high. A down-U distribution of the long spacing is found, which is mainly ascribed to the variation of thickness of crystalline lamellae with the depth. The results show that a higher level of lamellar orientation is not necessarily accompanied by a higher degree of linear crystallinity. [Copyright &y& Elsevier]