Influence of Pro-Oxidant on Photodegradation of a Low-Density Polyethylene-Nanosilica Composite

R.G. Zepp, O. Okungbowa, A.L. Andrady, J. Locklin, R. Arnold
US Environmental Protection Agency, US

Keywords: HDPE, nanosilica, composite, photodegradation, pro-oxidant


Use of polymer nanocomposites is burgeoning and they represent one of the fastest growing components of the manufactured nanomaterials market. Incorporation of nanoscale fillers in these plastics significantly improves their stiffness and other key mechanical properties. Although the properties of these materials are quite useful, little is known about their effect on environmental health and safety. The research presented here helps to address this lack of information by focusing on evaluating procedures that can reduce outdoor persistence of polymer nanocomposites. We provide initial findings on reducing the outdoor persistence of low-density-polyethylene (LDPE) nanosilica composites by enhancing their UV-induced degradation. In addition to reducing persistence, photodegradation is a potential pathway for the release of the nanosilica from the polymer matrix. The polymer nanocomposites were stable indoors where little UV exposure occurs, but degradation of the composites with pro-oxidant was greatly accelerated upon exposure to simulated sunlight. Adding pro-oxidant accelerated degradation by about one order of magnitude compared to a composite with no pro-oxidant. Changes in the LDPE- nanosilica composites were followed by changes in infrared spectroscopic properties (Fourier transform infrared spectroscopy), mechanical properties, atomic force microscopy (AFM), scanning electron microscopy and other procedures.