Authors: X. Gu, G. Chen, M. Zhao, S.S. Watson, D. Zhe, P.E. Stutzman, T. Nguyen, J.W. Chin, J.W. Martin
Affilation: NIST, United States
Pages: 709 - 712
Keywords: nanoparticles, nanocomposites, ZnO, long-term performance, UV exposure
This study is to investigate the role of ZnO nanoparticles in the life cycle of a waterborne polyurethane (PU) nanocomposite during UV exposure. The specimens were exposed to the NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) under different relative humdities at 45 C. The chemical changes of the exposed specimens were examined by Fourier Transform Infrared Spectroscopy and UV-visible spectroscopy. Changes in surface morphology were characterized by atomic force microscopy, electric force microscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy microanalysis. The results clearly show that the ZnO nanoparticles tend to be a catalyst to accelerate the photodegradation of the nanocomposites. This photo-catalytic effect is dependent on the size, the concentration, and the surface treatments of ZnO nanoparticles, as well as the exposure conditions (e.g. humidity, spectra wavelength of light). Additionally, the physical degradation mode including the aggregation and the release of nanoparticles in ZnO/PU nanocomposites during UV exposure was also shown. This study indicates that the effect of nanoparticles on the long-term performance of nanocomposites is significant but also complicated, suggesting that it necessary to develop new methodologies for service life prediction of new polymer composites.