Rheology of glass-fiber-filled polypropylene melts

The advantages of glass-reinforced plastics in various branches of the industry such as automotive and aircraft industries, and also in the manufacturing of furniture and sports goods are well-known. In all these applications knowledge of the melt flow of the composite material is required, in order to design machinery for processing the filled polymer. This paper is a contribution to the quantitative description of the rheology of glass-fiber-filled polypropylene melts. The effect of shear rate, melt temperature and fiber concentration on the melt viscosity have been studied by means of a high-pressure capillary rheometer. A novel equation has been presented to correlate the melt viscosity with the fiber content, using a modified shift factor taking the melt temperature and the fiber content into account. The proposed modeling can be applied to any filled thermoplastic melt.