Amine-Functionalized TiO2 Nanoparticles Covalently Loaded into Epoxy Networks via Thermal and Microwave Curing Processes

TiO2 nanoparticles were surface modified by NH2-functionalized organic moieties, and then chemically loaded into diglycidyl ether of bisphenol A-derived epoxy networks. Amine functionalization of these organically modified nanoparticles allowed them to have an efficient participation in the curing processes. Alongside the main amine hardener, i.e., 3,3 '-dimethyl-4,4 '-diaminodicyclohexylmethane, the aminated TiO2 played the role of a new inorganic co-hardener. Thermal and microwave-assisted curing processes resulted in epoxy-based composites incorporated by uniformly dispersed TiO2 nanoparticles. Diffuse reflectance ultraviolet-visible spectra showed that unlike the neat synthesized counterparts, TiO2-loaded epoxy composites have significant absorption in the visible range of 400-700 nm. According to the results obtained from atomic force microscopy technique, it was found that the microwave-assisted curing process results in a smoother surface in comparison with the thermal one. Transmission electron microscopy obviously demonstrated that the average size of the loaded particles is below 50 nm. Thermogravimetric analysis of the TiO2-containing epoxy networks revealed that the resulted composites are thermally decomposed through a simple one-step process at about 360 degrees C. Dynamic mechanical thermal analysis profiles indicated that no agglomeration of the nanoparticles occurs during the curing processes of the epoxy resin, and the incorporated nanoparticles somewhat limit the segmental motions of the polymer chains.