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Abstract: The morphology of isotactic polystyrene (iPS) particles which had been compounded into an isotactic polypropylene (iPP) matrix was varied in-situ by selective heat treatment to be either amorphous (iPSamorphous) or semicrystalline (iPScrystalline). The influence of iPS morphology on the quiescent and shear-induced isothermal crystallisation of iPP was then studied using differential scanning calorimetry (DSC), in-situ simultaneous small and wide angle X-ray scattering (SAXS/WAXS) and polarised optical microscopy (POM). In the quiescent condition iPScrystalline was found to selectively nucleate the β phase while iPSamorphous nucleated the α phase of iPP. Compared to the control sample (iPPcontrol), the presence of both morphologies of iPS increased the number of shear-induced oriented crystal precursors that form as a result of the step shear. During isothermal crystallisation the shear-induced nuclei promote oriented α form crystal growth, accelerate the crystallisation kinetics and ultimately swamp the effect of the nucleating particles present. [Copyright &y& Elsevier]

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]