Hydroxyapatite nanoparticles as novel low-refractive index additives for the long-term UV-photoprotection of transparent composite materials

Hydroxyapatite (HA) nanoparticles are introduced as a novel type of low-refractive-index additives for the formation of transparent polymer powder coatings. The beneficial effects of nano-HA for the long-term UV-photoprotection of polyester composite materials under accelerated weathering conditions are demonstrated in this work. These results are of considerable interest for the development of new hybrid organic-inorganic systems to be used as coating materials for outdoor applications such as transparent UV-resistant protection layers stabilized with functional nanoparticles based on cheap and biocompatible compounds.