Analysis of the interfacial interactions in polypropylene/silica nanocomposites

Polypropylene-based composites were prepared by melt blending with nano-silica, which was pre-treated by grafting polymerization onto the surface. Tensile moduli and strengths of the composites were determined as a function of the nano-silica content and the amount of the grafting polymers chemically attached to the nanoparticles, ie percentage grafting. To analyse the relationships between the interfacial interactions in the composites and tensile performance, a number of models dealing with the static and dynamic mechanical behaviours of the particulate composites were applied. It was found that stronger interfacial interactions exist in the grafted nano-silica-filled polypropylene composites as compared to the composites with untreated nano-silica. Since the interfacial interactions occur only within a very short range, the greatest interaction between the modified nanoparticles and the matrix is achieved in the case of low silica concentration and low percentage grafting. An increase in the percentage grafting for various grafted nanoparticles definitely results in an increase of interphase thickness, but the interfacial interactions and the tensile performance of the composites are not necessarily improved because the agglomeration structure of the nanoparticles and the miscibility between the components play the leading role. (C) 2003 Society of Chemical Industry.