Advanced UV Shielding for Cork: A comparative study of ZnO and TiO2 films through colorimetric and FTIR techniques

This study evaluates the potential of ZnO and TiO₂ films produced by magnetron sputtering to protect cork from the ageing effects induced by the solar radiation, particularly its UV component. This approach was validated first by exposure of cork under coated glass, and then extended to coated cork. The variation of color coordinates (L*, a*, b*) after exposure to a sun simulator lamp demonstrated that ZnO films provide superior protection compared to TiO₂ films. The TiO₂ coatings revealed to be not enough protective, exhibiting color variations (ΔC ≈ 9) even higher than the uncoated cork (ΔC ≈ 6). ZnO films showed a lower degree of color change and less UV-induced damage. (3.6 ≤ ΔC ≤ 5.0). Thus, ZnO films can effectively reduce the impact of UV radiation on cork, offering a more reliable protective solution. This study includes also the analysis of Fourrier Transform Infrared Spectra (FTIR) of the samples before and after exposure test. The exposure of the unprotected samples to the radiation causes a large reduction the of intensity of the FTIR bands, a phenomenon which is greatly reduced when cork protected by ZnO films. A correlation between color variation and intensity of FTIR spectra was established.