Studies on the combined effect of injection temperature and fiber content on the properties of polypropylene-glass fiber composites

This paper focuses on correlations between physical and mechanical properties of polypropylene (PP) and PP/glass fiber composites molded at different injection temperatures and fiber weight fractions (20% and 30% w/w). Density, melt flow index (MFI), thermal stability, crystallinity and tensile and impact properties have been evaluated. The MFI of the composites was dependent on fiber content, fiber length distributions, a slight additional thermal protection due to the fibers and PP chain scission. The tensile strength and elastic modulus of the PP-composites increased linearly with fiber content. Injection temperature was shown to decrease elastic modulus to a point that the different composites showed statistically comparable rigidities. These properties have been discussed in the light of microstructural changes studied by SEM.