Mechanical and thermal properties of syndiotactic polypropene filled with glass beads and talcum

Glass bead-and talcum-reinforced polypropene composites based on syndiotactic polypropene (s-PP) and isotactic polypropene (i-PP) were prepared to study mechanical and thermal properties and to identify influence of PP type and stereoregularity. Composites based on s-PP gave higher notched Izod impact strength than those based on i-PP, accompanied by lower Young's modulus and yield stress. The experimental Young's moduli and yield stresses of composites based on highly stereoregular s-PP and i-PP were in good agreement with theoretical predictions according to Kerner and Nicolais-Narkis, respectively. The higher relative Young's modulus and yield stress of composites based on s-PP of low stereoregularity were attributed to strong interfacial adhesion and can be described by the theory of Jancar. Lap shear tests confirmed strong glass polymer interactions. Investigations of crystallization show the nucleating effect of glass beads and talcum in the case of i-PP as well as s-PP. With increasing filler volume fraction, PP degree of crystallinity decreases. Dynamic mechanical analysis of glass bead-reinforced s-PP composites show an unexpected relaxation occurring at 55 degrees C. (C) 1997 Elsevier Science Ltd.