Waterborne polyurethane acrylate/surface-modified γ-Al2O3 (WPUA/SAl2O3) nanocomposite films were prepared via a UV-initiated free radical photopolymerization system composed of nanocomposite emulsion, reactive diluents and a photoinitiator. To improve the compatibility of inorganic and organic phases, γ-Al2O3 nanoparticles were surface-modified by γ-methacryloxypropyl trimethoxysilane and combined with a WPUA matrix. The WPUA oligomer was initially prepared by step-growth polymerization, and the content of hydrophilic chain extender, dimethylolpropionic acid (DMPA) was varied to investigate its effect on the properties of the oligomer emulsion. Performance of nanocomposite films with various loadings of SAl2O3 was evaluated by TGA and DSC, water uptake/swelling degree, surface wettability, tensile strength and elongation at break, etc. The results revealed that thermostability of the nanocomposite film was reinforced compared with the WPUA matrix. Swelling capacity and mechanical strength were also improved due to the increase of crosslinking density. Moreover, the optimum content of DMPA for oligomer synthesis was 5%.

Keywords: waterborne polyurethane acrylate; nanocomposite films; surface-modified γ-Al2O3; dimethylolpropionic acid