Tribological properties of epoxy + silica hybrid materials

Various amounts of nano size silica particles prepared by a sol-gel process were added to epoxy+ amine systems. We have investigated tribological properties including friction and sliding wear resistance of hybrids so obtained, and also relationships between different tribological properties and surface topography. The thermal degradation behavior and thermal stabilities were determined by thermogravimetric analysis (TGA). The introduction of silica into bisphenol-A type epoxy resins does not affect significantly char formation in the epoxy resins; relatively small improvements in thermal stabilities is seen. At the same time, results from a pin-on-disc tribometer show that silica addition causes lowering of friction already at 1 part per hundred (phr) and very significant lowering of wear at 2 or more phr. We have found finer waves of the worn surface in the hybrids than in the neat epoxy. SEM results demonstrate that the silica particles improve the wear resistance by hindering crack propagation.