This study was carried out on nanocomposites consisting of nanometer silica fillers embedded in thermoset polymers that were prepared via the in situ polymerization of ultraviolet (UV) curable systems containing different contents of nanometer silicas by irradiation of UV light. Because of the introduction of nanosilicas, the curing rates of the UV curing of dispersing systems were played down; that is, the curing times were prolonged, but the mechanical properties of the nanocomposites, such as tensile strength and Young's modulus, increased, and the thermostability of the nanocomposites at temperatures lower than 400 K improved. The dispersing states of nanometer silicas within the polymer matrix were characterized by transmission electron microscopy, and the results show that the nanometer silicas had good homogeneously dispersing states within nanocomposites containing less than 3 wt % nanometer silicas.

The nanocomposites consist of nanometer silica fillers embedded in thermoset polymers, which were prepared by means of irradiation of ultraviolet light. The nanomechanic properties had been investigated by load–displacement analysis from nanoindentation experiments. The results obtained showed that the nanoindentation hardness is decreasing and tends to a certain value with increasing indentation depth, the value is among 1.91–4.11 GPa while the nanosilica contents varied from 0 to 5% within nanocomposites. Young’s modulus measured by nanoindentation is higher than the value by tensile test, namely EI = ET 1/4 2: 63 and the enhancement of Young’s modulus due to the presence of nanosilica with the above contents, EI = EI, 0 1/4 1: 7 2: 0 from 1: 8 2: 2 from tensile test, was compared to be consistent with each other in two different methods. So nanoindentation technique has been successfully applied for the valuation of the nanomechanic properties of nanocomposites with nanosilica.