Epoxy composites reinforced by different size silica nanoparticles

Three series of epoxy/SiO₂ composites, containing 0.3–7 wt % nanosized SiO₂ with different specific surface area, were prepared by solution blending. The resulting composites exhibit the higher glass transition temperature (T_g) than that of pure epoxy. The T_g of composite showed a maximum increment of 35.3°C by the addition of 7 wt % A300. The trade name of A300 is Aerosil 300. It is one of the fumed silica nanoparticles products of Degussa. The decomposition temperatures (T_d) of composites were always higher than that of pure epoxy and showed a maximum increment of 20.8°C by the addition of 5 wt % A300. The light transmittance of composites was as a function of the SiO₂ content and size. The water permeability of composites decreased with increasing SiO₂ content and the 7 wt % A300 composite exhibits a maximum decrement percentage of 35.6%. The T_g, T_d, storage modulus, and water‐vapor barrier property are as a function of the SiO₂ content and size. These properties increased as the content of SiO₂ increased. The finer SiO₂ are more effective in increasing the T_g, T_d, and water‐vapor barrier property. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010