In this study, the role of the nanoparticle/polymer interface in the long-term UV weathering performance of a nano-ZnO filled polyurethane (PU) coating system was investigated. The effects of the parameters that can influence the particle/polymer interfacial properties, such as size, loading, surface modification of the nanoparticles, on photodegradation of ZnO/PU films were evaluated. The nature of the interfacial regions before and after UV exposures were characterized by atomic force microscopy (AFM)-based techniques. Results have shown that the interfacial properties strongly affect chemical, thermo-mechanical and morphological properties of the UV-exposed ZnO/PU films. By combining tapping mode AFM and novel electric force microscopy (EFM), the particle/polymer interfacial regions have been successfully detected directly from the surface of the ZnO/PU films. Further, our results indicate that ZnO nanoparticles can function as a photo-catalyst or a photo-stabilizer, depending on the UV exposure conditions. A hypothesis is proposed that the polymers in the vicinity of the ZnO/PU interface are preferentially degraded or protected, depending on ZnO nanoparticles act as a photo-catalyst or a photo-stabilizer in the polymers. This study clearly demonstrates that the particle/polymer interface plays a critical role in the long-term durability of nano-filled polymeric coatings.
Conference Dates: April 12-14, 2010
Conference Location: Charlotte, NC
Conference Title: American Coatings Show 2010
Pub Type: Conferences