Effect of Gold Nanoparticles on the Physical Properties of an Epoxy Resin.

The effect of doping the bisphenol A diglycidyl ether (DGEBA)/m-xylylenediamine (mXDA) system with gold nanoparticles (AuNP) has been studied with differential scanning calorimetry (DSC), thermogravimetric analysis, dynamic mechanical analysis (DMA), and dielectric analysis (DEA). The evolved heat (ΔH(t)), the glass transition temperature (T(g)), and the associated activation energies of this relaxation process have been determined. Below a certain concentration of AuNPs (=8.5%, in mg AuNP/g epoxy matrix), T(g) decreases linearly with the concentration of AuNPs, but above it, T(g) is not affected. The degree of conversion α of this epoxy system was analyzed by the semiempirical Kamal's model, evidencing that diffusion correction is required at high values of α. Activation energy values suggest that AuNPs can cause some impediments at the beginning of the crosslinking process (n-order mechanism). The slight difference between the initial decomposition temperature, as well as the temperature for which the degradation rate is at a maximum, for both systems can be accepted to be within experimental error. Mechanical properties (tension, compression, and bending tests) are not affected by the presence of AuNPs. Dielectric measurements show the existence of a second T(g) at high temperatures, which was analyzed using the Tsagarapoulos and Eisenberg model of the mobility restrictions of network chains bound to the filler.