MECHANICAL AND THERMAL-PROPERTIES OF SYNDIOTACTIC POLYPROPENE FILLED WITH GLASS-BEADS AND TALCUM

Glass bead-and talcum-reinforced polypropene composites based on syndi otactic polypropene (s-PP) and isotactic polypropene (i-PP) were prepa red to study mechanical and thermal properties and to identify influen ce of PP type and stereoregularity. Composites based on s-PP gave high er notched Izod impact strength than those based on i-PP, accompanied by lower Young's modulus and yield stress. The experimental Young's mo duli and yield stresses of composites based on highly stereoregular s- PP and i-PP were in good agreement with theoretical predictions accord ing to Kerner and Nicolais-Narkis, respectively. The higher relative Y oung's modulus and yield stress of composites based on s-PP of low ste reoregularity were attributed to strong interfacial adhesion and can b e 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 we ll as s-PP. With increasing filler volume fraction, PP degree of cryst allinity decreases. Dynamic mechanical analysis of glass bead-reinforc ed s-PP composites show an unexpected relaxation occurring at 55 degre es C. (C) 1997 Elsevier Science Ltd.