Preparation and Characterisation of Epoxy Composites Filled with Silica Nanoparticles

A series of epoxy/SiO₂ composites, containing 0.5, 1, 3, 5, and 7 wt.% SiO₂ nanoparticles, were prepared by solution blending. Differential scanning calorimetry (DSC) indicated that the glass transition temperatures (T_g) of the composites were higher than that of the pure epoxy and rose as the SiO₂ content increased. The decomposition temperatures (T_d) of the composites were always higher than that of the pure epoxy, the maximum increase of 20.8 °C being achieved with the addition of 5 wt.% SiO_2. The light transmittance of the composites was still higher than 80% with up to 7 wt.% SiO₂. The water permeability of the composites decreased with increasing SiO₂ content, and the 7 wt.% SiO₂ produced a composite with the maximum permeability decrease of 56.3%. Scanning electron microscopy (SEM) showed that finer silica was dispersed in the epoxy matrix without large agglomerates.