Microproperties of Colloidal Silica/ Acrylic UV-curable Nanocompoditie Clearcoats Comperative Methods to Evaluate Scratch Abrasion

Organic coatings are well known to be sensitive to scratch, abrasion and chemicals. In these last few years, research was focused on the preparation of nanocomposite coatings which bring partial answers to these issues. One way to prepare nanocomposites is to use concentrated silica organosols where the continuous organic phase can be either monomers, oligomers or volatile solvents. These commercially available products contain up to 50 % of monodisperse silica particles sizing between 10 and 100 nanometers. Once thermally or UV/EB cured, the nanocomposite coatings are found to resist well to scratching, to abrasion and to aggressive chemicals, while maintaining transparency and gloss. In this work, we will discuss on the effect of silica particles on the improvement of viscoelastic properties of acrylic UV-curable clearcoats, on surface hardness, on scratch and on abrasion as measured by Dynamic thermal analysis (DMA), Micro-indentation, Erichsen and Scotch-Brite scratch tests, Pencil hardness and Taber abrasion tests. AFM and SEM high resolution microscopy were used to locate the nanoparticles in the coating.