Self cleaning TiO2 coating on polycarbonate: Surface treatment, photocatalytic and nanomechanical properties

A developed route to form TiO2 self cleaning coatings on polycarbonate substrates is reported. TiO2 coatings on plastics may find widespread application in auto and construction industries if possess desired photocatalytic and mechanical properties. A chemical surface treatment method was used to create hydrophilic groups on the surface. X-ray photoelectron spectroscopy showed the treatment led to the oxidation of surface groups. TiO2 deposition was based on wet coating using an anatase sol of TiO2 nanoparticles of 30 nm size. The sol was synthesized using a sol-gel route. A pre-coat of peroxotitanium complex was employed to improve adhesion and inhibit the substrate degradation. The coating reduced the transparency for 10-15%. The photocatalytic activity was found linearly dependent on the thickness. The reaction rate constant for methylene blue degradation was estimated 0.024 s− 1 for films of 150 nm thickness. The mechanical properties were also improved after coating, as demonstrated by nano-indentation and nano-scratch tests. The hardness and scratch resistance were improved by 2.5 and ∼6.4 folds.