Influence of coupling agents on material behaviour of glass flake reinforced polypropylene

This paper presents a study evaluating the effects of aminosilane and titanate coupling agents on the material properties of glass flake reinforced polypropylene and compares the results with pure polypropylene and untreated glass flake reinforced polypropylene. Tensile and flexural properties, impact resistance and residual stresses are strongly dependent on the type and level of coupling agent employed, whereas changes in melt-crystallisation and crystalline content of the polypropylene in the composite materials was minimal. Glass flakes modified with aminosilane gave higher stiffness and strength than the titanate treatment. Thermal expansion hysteresis provided an indication of the relative levels of residual stresses in the polymeric materials, which was verified using the layer removal method for determining residual stress distributions. Ultrasonic velocity measurements conducted on the composite materials before and after exposure to sub-zero temperatures proved useful in assessing the effectiveness of the various surface treatments in promoting interfacial adhesion.