TiO2-SiO2 hard coating on polycarbonate substrate by microwave assisted sol-gel technique

To enhance the poor scratch resistance ofpolycarbonate, a silica (SiO2) and titania (TiO2) transparentinorganic coatings was designed and synthesized using amicrowave assisted sol–gel heating. Due to the transparencyof PC to microwave, the idea was to obtain a localizedheating only on the coating film. The obtained films werefully characterized to mainly evaluate the effect of titaniacontent, added both as nanoparticles and from tetraethylorthotitanate, TEOT, on scratch resistance and surfacemorphology. Particular attention was paid to preserve thetransparency of the final product. The results allowed todefine that TEOT addition enhances the adhesion betweencoating and polycarbonate, even if the optimized quantityhave to be defined in order to avoid a decrease of coatingmechanical resistance. In this work optimized TEOT levelresults to be the associated to 5 wt% of TiO2, which enablethe better balancing between adhesion and mechanicalresistance performances.