INFLUENCE OF AN OPTIMIZED INTERPHASE ON THE PROPERTIES OF POLYPROPYLENE GLASS FIBER COMPOSITES/

To ensure efficient transfer of stress between glass fibres and polypr opylene (PP) matrix, the fibres are sized and the matrix is chemically modified. In this study, the interphase properties of glass fibre/PP model composites have been investigated using fibres sized with gamma- aminopropyltriethoxysilane (A1100) and various polymer dispersions (po lyethylene/polyurethane (PE/PUR), PP, PP/PUR and epoxy) and unmodified (PP) or modified (PPM) matrices. The acid-base properties of the fibr e surfaces were characterized by zeta potential measurements in electr olyte solutions with varying pH. Fibre-melt interaction was characteri zed by direct wetting measurements of polymer melts on fibre surfaces and single-fibre pull-out tests under conditions comparable to process ing conditions. Composite mechanical properties influenced by fibre-me lt interaction were tested using continuous fibre-reinforced polypropy lenes. The direct fibre-melt wetting experiments provided evidence for acid-base interactions together with interdiffusion effects in the in terphase between sized glass fibres and the modified polypropylene mat rix or physical interactions at the fibre-polymer melt interface. It w as proved that these physical or chemical interactions influence the i nterfacial shear strength and the macromechanical properties. Differen ces in the interfacial shear strength correlated with different wettin g kinetics due to the different formulations of film former used.