Composites from functionalized polyolefins and silica

The effect of diethyl maleate (DEM) units grafted to the polyolefins on the compatibility with inorganic fillers has been investigated. Ethylene-propylene rubber functionalized with DEM (EPR-g-DEM) was mixed with silica in different weight ratios using a Brabender mixer (Plastograph), by comparing analogous mixtures prepared starting with unmodified ethylene-propylene-rubber (EPR) and silica. The Torque traces showed that the diethyl maleate grafted on the EPR significantly changed the interfacial interaction between the silica surface and the EPR during the mixing process. Incorporation of silica into either EPR and EPR-g-DEM by mechanical mixing produced a fraction of insoluble by association with the filler (bound rubber), as revealed by the solvent extraction technique. Bound rubber evaluations pointed out the major capability of the EPR-g-DEM to interact with the mineral surface. In this case specific interactions involving the carbonyl groups of the functionalized polyolefin and the polar sites on the filler surface have been identified by means of FT-IR spectroscopy. As revealed by SEM observations, these specific interactions at the interface promote the mutual wettability and adhesion of the components in EPR-g-DEM/silica composites.