Organic/inorganic nanocomposite coating of bisphenol A diglycidyl ether diacrylate containing silica nanoparticles via electron beam curing process

The paper presents the fabrication of organic/inorganic nanocomposite coatings via a solvent free, environment benign-electron beam curing process using Bisphenol A diglycidyl ether diacrylate (BDGDA) as an oligomer, 1,6-Hexandioldiacrylate (HDDA) as a reactive diluent, and SiO2 nanoparticles as inorganic nano-reinforcing component. Silica nanoparticles were modified by 60Co-gamma radiation induced grafting of glycidyl methacrylate (GMA) and 2-hydroxyethyl methacrylate (HEMA), before dispersing them into coating compositions for their better compatibility with coating formulations. Surface modified silica nanoparticles were characterized by FTIR spectroscopy and thermogravimetric analysis (TGA). The rheological behavior of coating formulations was evaluated using Brookfield viscometer; formulations with surface modified SiO2 nanoparticles exhibited pseudoplastic type non-Newtonian behavior. EB cured nanocomposite coatings were characterized by TGA, differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle (wettability) measurement. AFM and SEM analysis showed that the dispersion of silica nanoparticles in the coatings improved after surface modification. DSC analysis showed that the modification of SiO2 increased the glass transition temperature (Tg) of the EB cured coatings. Coatings were further analyzed for performance properties, viz. abrasion resistance, gloss at 60° angle, pencil hardness, pendulum hardness, chemical and steam resistance properties, as per standard test methods. It was found that incorporation of silica nanoparticles into coating formulation improves abrasion resistance significantly. Gloss of coating reduced significantly upon addition of silica nanoparticles suggesting that the silica nanoparticles could be used as effective matting agent. Moreover, modification of silica nanoparticles further improved abrasion, pencil hardness and gloss significantly. EB cured nanocomposite coating passed chemical and steam resistance tests and exhibited excellent chemical and stain resistance properties.