Dynamic Mechanical Measurements of Epoxy Matrix-Silica Nanocomposites II

The mechanical properties of epoxy-silica nanocomposites have been studied; the silica nanosphere fillers used were un-functionalised, functionalised with amine, with epoxy, or a mixture of both kinds. Dynamic mechanical analysis measurements revealed an increase in the shear storage modulus, for all samples with a filler content of 3-5%. Improvements were observed in the glassy and rubbery states, without affecting the glass transition temperature of the materials. Above these strengthening percentages, the mechanical properties began to deteriorate, but in all cases they remained superior to those of the pristine epoxy resin. For low strengthening percentages, samples reinforced with both nanospheres functionalised with amine and with epoxy showed better mechanical behaviour. As the strengthening percentage increased, materials reinforced with silica nanoballs functionalised with epoxy groups alone showed higher mechanical strength than the rest. To improve the mechanical properties of these systems, it was important to optimise both the percentage of added filler and the type of reinforcement. The parameter determining the flow stress was the cohesion of the solid state, which was represented by the storage modulus in shear.