Synthesis and characterization of scratch-resistant hybrid coatings based on non-hydrolytic sol-gel ZrO2 nanoparticles

Hybrid transparent coatings based on zirconia nanoparticle fillers and epoxy resin were designed to increase scratch resistance of commodity polymers without impairing their optical properties. Suspensions of nano-crystalline ZrO2 in benzyl alcohol were synthesized via a versatile non-hydrolytic sol-gel process using ZrCl4 as precursor. The obtained ZrO2 nanoparticles showed a crystalline structure attributable to a tetragonal phase and an average particle size of 2 nm. ZrO2 nanoparticles, suspended in tert-butanol, were mixed with a commercial epoxy resin (5 and 10%wt.). The organic solvent was then evaporated and hybrid composites were deposited on polycarbonate and poly(methyl methacrylate). The obtained coatings showed a homogeneous adhesion and a negligible effect on the transparency of these polymers. An increased scratch-resistance was obtained by increasing the ZrO2 nanoparticles content.