The main factors of the environment which cause the weather
degradation of organic coatings are ultraviolet radiation, oxygen
and water. To reduce damages due to UV radiation, UV absorbers
are often incorporated in organic coatings. Organic absorbers suffer
from migration and degradation over time, so they do not
exhibit long-term stability in coatings. Inorganic UV absorbers do
not migrate so they can provide long-term protection and are more
and more widely used. Due to their small size,the nanoparticles can
be used at low concentration without disturbing the other coating
properties.
Zinc oxide is an inorganic UV absorber having a wide band gap
energy and used as UV stabilizer in organic coatings [1–4]. The nano
ZnO was investigated as UVabsorber in a polyurethane/acrylic clear
topcoat. The influence of ZnO concentration and film thickness on
the UV protection was investigated and the results show that the
presence of nano ZnO at 2.0 g/m2 can block more than 99% UV
radiation [1]. The nano ZnO and silica-coated nano ZnO improved
the exterior durability and physic-mechanical properties of the
acrylic waterborne coatings for wood [2,3]. The presence of nano