Effect of surface modification of nanosilica by hydride-groups on morphology, strength and resistance of epoxy-composites

Abstract

A chemical modification of fumed silica surface by active groups can enlarge its functional capabilities as a polymer filler. As a result, a new possibility in the formation of reinforced polymeric composites appears.In this work, silica with grafted silicon hydride (≡Si–H) groups was found to be active in the processes of hydrosilylation of active bonds in monomers during their polymerization. Hydride-silylated silica was obtained via his treatment with triethoxysilane. The presence of grafted silicon hydride groups was confirmed by means of IR spectroscopy, and their concentration measured by titrimetric and spectrophotometric analysis was found to be about 0.4 mmol/g. Silica-epoxy composites were prepared and the resulted materials after curing were subject to compression, bending, micro-hardness and adhesion mechanical tests.According to experimental results, the synthesized hydride-silica fillers let to enhance the important strength properties of the epoxy-polymer already at 2 wt% loading. In particular, the elastic modulus for compression increased by 30–40%, the one for bending – by 1.2–1.5 times, the flexural strength – by 1.5–2 times, and adhesion to steel – by 2.5–2.8 times. These effects are achieved due to good compatibility and homogeneous distribution of the filler in the resin, as shown by SEM microscopy (after hydride-modification, the silica agglomerates in epoxy disappear). IR-spectroscopy shows a possible increasing of epoxy conversion's rate after 2%-filling by hydride-silica. Thus, preliminary results indicate that fumed silica with grafted silicon hydride groups shows promise as active reinforcing filler for epoxy polymers.The work demonstrates the potential of nanosilica filler surface hydride-silylation for low-cost strengthening of epoxy polymers for industry and repair.