The thesis presents a study into the surface properties of silica and determining the silica surface thermodynamic. The effect of silica surface energies on the disperbility of silica in the elastomer phase has been computed for the first time, this is made possible by silanising the silica sample with a series of coupling and non-coupling organosilanes having a range of functional groups. The relationship between the surface chemistry and surface energies, as determined by thermogravimetry combined with an infrared spectroscopy (TGA-IR) and Inverse Gas Chromatography (IGC) respectively is investigated, resulting in a coherent understanding of the modified silica surface thermodynamics of various organosilanes.

IGC analysis enabled the determination of the specific surface energy/ dispersive surface energy profiles of modified silicas at different surface coverage. A property of particular interest is the work of cohesion of silica particles, which is found to be correlating well with silica microdispersion in the elastomer phase, as determined using a TEM-network visualisation method and dynamic mechanical analysis (DMA) where the hysteresis effects were greatly reduced for silanised silica-filled vulcanisates. From this study, it is clear that surface energy measurements could be used as a good indication and explanation of the dispersibility of silica in the elastomer phase.

From all the silica-filled vulcanisates considered in this study, it is observed that significant improvements in tensile strength, reinforcement index, angle tear and DIN abrasion resistance were shown by silicas modified with coupling organosilanes. Both types of organosilanes improved the less abrasive Akron abrasion resistance compared to untreated silica-filled vulcanisate, but there was no clear difference between the two types. This investigation opens up some possible routes to improving tyre tread compound design.