Evaluation of interfacial interaction in polypropylene surface treated CaCO3 composites

Interfacial interactions significantly influence the properties of particulate filled polymers. The adhesion between the particles and the polymer matrix depends on the size (area) of the interface and the strength of the interaction. While the former quantity is related to the specific surface area of the filler, the strength of the interaction can be modified by its surface treatment. In the current experiments polypropylene composites were prepared which contained different amounts of filler treated with eight functional trialkoxy silane coupling agents and the routinely used stearic acid, for comparison. Tensile properties of the composites were determined and the effect of interfacial interaction was evaluated by semi-empirical equations developed previously. Significant difference was detected in the effect of the various silane coupling agents. Amino functional silanes increase the strength of the interaction considerably. The other coupling agents reduce the surface tension of the filler, which leads to a decrease in the reversible work of adhesion between the filler and the polymer. These changes result in a decrease in the tensile strength of the composite. The results also prove the validity of the model equations applied. Parameter B, a measure of the strength of the interaction, was calculated for each silane coupling agent thus quantitatively characterizing their effectiveness. (C) 1998 Elsevier Science Limited. All rights reserved.