Epoxy composites reinforced by different size silica nanoparticles

Three series of epoxy/SiO 2 composites, containing 0.3–7 wt % nanosized SiO 2 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 SiO 2 content and size. The water permeability of composites decreased with increasing SiO 2 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 SiO 2 content and size. These properties increased as the content of SiO 2 increased. The finer SiO 2 are more effective in increasing the T g , T d , and water‐vapor barrier property. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010