Role of Thickness, Silanization, and Tungsten Oxide Nanoparticle Content in <scp>UV</scp> ‐Shielding of Polyvinyl Butyral

ABSTRACT Long‐term exposure to UV‐A and UV‐B radiation presents critical risks to human health. In southern Brazil, these risks are intensified by the South Atlantic Magnetic Anomaly, which weakens atmospheric shielding. This study evaluated the role of nano‐sized WO 3 particles dispersed in a transparent PVB matrix for UV‐shielding. Nanocomposites with 2.5%, 5.0%, and 7.5% w/w WO 3 , both pristine and silanized, were prepared via solvent casting and high‐energy sonication, producing films of 8 and 30 μm thickness. TGA results indicated enhanced thermal stability in thinner films, with a 19% improvement in T 5% for a 7.5% w/w pristine WO 3 sample. DSC measurements showed variations smaller than 4°C in glass transition temperatures with increased nanoparticle content, regardless of surface treatment. Pristine WO 3 nanocomposites exhibited a 40% increase in elastic modulus and nano hardness compared to neat PVB. Samples showed increased UV‐A and UV‐B blocking with higher nanoparticle content. In thinner films, silanized nanoparticles achieved superior UV‐blocking performance, reaching 60% UV‐shielding with 7.5% (w/w) WO 3 , likely due to improved dispersion, as verified by NNDi analysis. The opposite effect was observed in thicker samples, with 7.5% (w/w) of pristine WO 3 samples achieving over 90% UV‐shielding.