In situ rheo-x-ray investigation of flow-induced orientation in layered silicate-syndiotactic polypropylene nanocomposite melt

Abstract

This article describes experimental results for both the rheology and flow-induced orientation of a series of intercalated syndiotactic polypropylene nanocomposites which were prepared by melt intercalation in the presence or absence of an i-PP/maleic anhydride copolymer. The nanocomposites showed typical rheological signatures of well-dispersed interacalated nanocomposites such as a low frequency plateau in dynamic moduli and an apparent yield transition from very high viscosity at low shear stresses to low viscosity above a yield stress. In situ x-ray diffraction (XRD) measurements during shear provided direct evidence of rheology-microstructure links in these materials. It was found that the clay tactoids could be easily oriented by shear and that a high degree of orientation can be achieved after the yield transition. Further, the rheo-XRD apparatus allowed measurements of the relaxation of orientation upon the cessation of flow. The orientation relaxation time matched the characteristic relaxation times estimated from independent rheological measurements well.