Long term degradation kinetics and UV shielding efficiency of TiO2 and ZnO coatings on rubber and cork substrates
Authors
Tiss B., Martínez-Martínez D., Mansilla C., Baron E.L., Disdier A., Cunha L.
Reference
Applied Surface Science, vol. 695, art. no. 162940, 2025
Description
This work investigates the application of transparent oxide coatings to enhance the UV resistance of rubber and cork, and it explores their degradation kinetics under accelerated UV exposure. Thus, TiO2 and ZnO of varying thicknesses were deposited using magnetron sputtering on both substrates. TiO2 films were amorphous with dense morphology (thickness: 72 ± 3 nm to 130 ± 3 nm), while ZnO films were polycrystalline with nanocolumnar growth (thickness: 160 ± 4 nm to 580 ± 5 nm). Both films were UV-opaque, visible-transparent, with higher band gap energy for TiO2 (3.91–4.05 eV) than ZnO (3.25–3.29 eV), decreasing with thickness. Color spectrophotometry and FTIR revealed coating and UV-induced changes, with exponential fittings yielding maximum damage (ΔC∞) and damage rate (K). Uncoated cork degraded 4–5 times slower than rubbers, while films provided greater protection to rubbers. ΔC∞ values demonstrated that coatings effective on one rubber worked well on others, with rubbers classified into four categories by UV resistance. Consistently, ZnO-coated samples exhibited the best performance, except for the thinnest ZnO film, whose worse performance was attributed to a UV–Vis shoulder which allowed penetration of radiation of higher energy. TiO2 films slightly accelerate the degradation kinetics of cork, probably due to some catalytic effect at the interface.
Link
doi:10.1016/j.apsusc.2025.162940
