The efficiency of mechanical reinforcement in glass fibre-reinforced thermoplastics (GFRTP) depends, amongst other factors, on glass-fibre attrition during its processing and also on the degree of polymer-fibre interfacial interactions. In this work, the influence of material and processing parameters (matrix polymer viscosity, temperature profile, screw rpm and configuration) in a corotating twin-screw extruder and of the fibre-matrix interfacial interactions (PP-g-MAH as interfacial compatibilizer), were investigated to determine the mechanical properties of polypropylene (PP) composites with 30% glass-fibre (GF) sized with an aminosilane. The main processing parameters contributing to reduced attrition of GF were those that allowed lower polymer melt viscosity in the mixing/kneading zone of GF in the extruder, whilst increase in screw-rpm and higher shearing screw-profile, in spite of reducing the GF length, both contributed towards higher fibre wetting and interfacial adhesion, and thus resulting in improved tensile strength (TS) and lower Izod impact strength (IIS) of the composite. The use of PP-g-MAH compatibilizer contributed towards substantial increases in GF length and interfacial adhesion; thereby resulting in significant improvements in both TS and IIS of the composite.
Composites; polypropylene; glass-fibres; compounding; twin-screw extruder; mechanical properties; interface; PP-g-MAH compatibilizer
