INTERFACIAL SHEAR-STRENGTH OF NUCLEATED SHORT GLASS-FIBER REINFORCED POLYPROPYLENE

Polypropylene and the short glass-fibre-polypropylene composite in the form of granules were each initially pre-mixed with a sodium benzoate nucleating agent in a dry blender and subsequently homogenized in a twin-screw extruder. The extrudate was masticated and compression moulded. The inherent fibre orientation K and the interfacial shear strength tau of the short glass-fibre-polypropylene composite were determined by use of the short fibre composite theories proposed by Kelly and Tyson and modified by Bowyer and Bader. The interfacial shear strength tau and orientation factor K values of 18 MPa/0.201 and 24 MPa/0.177 were obtained for the nucleated and the unnucleated composite, respectively. The nucleated composite showed decreased interfacial shear strength and increased orientation factor, as was expected. The interfacial shear strength of the unnucleated samples compared favourably with the literature values.