Synthesis and characterization of the nano alumina-filled tetraglycidyl-4, 4′-diaminodiphenylmethane epoxy resin

In this study, the in situ incorporation of the inorganic alumina nanoparticles into the reactants of tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) epoxy resin represented an efficient way for the preparation of alumina/TGDDM nanocomposite. The surface modification of the alumina nanoparticles was carried out using two individual silane coupling agents, namely, aminopropyltriethoxysilane (APS) and glycidoxypropyltrimethoxysilane (GPS). The degree of silane grafting was evaluated for both coupling agents using FTIR spectroscopy and thermogravimetric analysis. The epoxy equivalent weight (EEW) of the epoxy resin in addition to the weight percentage of the lost nanoparticles during TGDDM polymerization was used as measurements of the polymerization yield. The neat nano alumina has more adverse effect on the epoxy EEW value (171 g/mol) than both silane-modified nano alumina (143–157 g/mol, depending on the reaction conditions). The degree of nano alumina dispersion in the epoxy matrix was investigated using SEM micrographs. The longer and more deflected crack pathways on the fractured surface of the alumina/TGDDM nanocomposites may be attributed to a relatively good degree of dispersion of the silane-modified alumina nanoparticles in the epoxy matrix. Compared to neat alumina, the better dispersion of the silane-modified alumina nanoparticles may be related to the improved interfacial interactions between the oxiran or amine groups available on the silane-modified alumina nanoparticles and the TGDDM epoxy functional groups. Besides, the higher exothermic heat of cure (i.e., 30–53 %) as evidenced in differential scanning calorimetry may be due to a rather good state of dispersion of silane-modified alumina nanoparticles.