Bimodal filler system consisting of mesoporous silica particles and silica nanoparticles toward efficient suppression of thermal expansion in silica/epoxy composites

Here we propose a bimodal inorganic filler system consisting of mesoporous silica particles and fine silica nanoparticles to fabricate silica/epoxy composites with low thermal expansion property. Two types of inorganic fillers are mechanically mixed with epoxy resin firstly. Then, by adding a curing agent, silica/epoxy composites are prepared. From TEM observation, it is proved that both mesoporous silica particles and silica nanoparticles are well dispersed in the composites. Through the theoretical calculation, more than 90 vol% of the mesopores is estimated to be filled with the epoxy polymers. Various types of the composites are prepared by changing the amounts of doped silica nanoparticles. (The amounts of doped mesoporous silica particles are constant.) Their thermal expansion behaviours are systematically investigated by using thermal mechanical analysis (TMA). With the increase of the amounts of silica nanoparticles, the glass transition temperatures (T(g)) are gradually shifted to the higher temperature range and the coefficient of linear thermal expansion (CTE) values are decreased. Thus, by utilizing the bimodal inorganic filler system, we can efficiently reduce thermal expansion in the silica/epoxy composites.