Synthesis of silica nano particles, their usage in automotive hybrid coatings and evaluation of their performances

The aim of the thesis is to develop and evaluate organic-inorganic hybrid coatings using modified nanoparticles for automotive paint applications. For this purpose, surface modifications were performed with different organic surface treatment chemicals. By using surface treated nanoscale (<100nm) silica particles, development of 2K and low bake temperature needed hybrid transparent coating i.e.,clearcoat formulation was tried to design. Nanoscale silica particles were produced from TEOS based on the "sol-gel" method. As a result of the experimental design, the inorganic silica particle concentration and particle sizes in methanol were obtained as 9.54% and 67nm respectively in addition to being stable. The surfaces of the inorganic silica particles of the solution, whose production was successfully carried out, were modified with silane chemicals containing different functional groups. Characterization of surface modified silica particles was performed by FTIR, TGA and SEM analyzes. As a result of the evaluations, it was found that optimum silica (solid): silane ratio is 1: 0.5. As a result, by using surface treated nanoscale silica particles, hybrid transparent topcoat i.e., clearcoat formulation were designed for automotive industry. The rheology of the developed hybrid clearcoat, kinetics of its film formation, its viscoelastic behavior before and after film formation and its surface physicochemistry were characterized. According to performance evaluation results, 1.75 per hundred resin usage of surface treated silica provided a positive effect on the performance of the hybrid clearcoat and improved its scratch resistance by 80%.