Enhanced photodegradation of titania loaded polyethylene films in a humid environment

Abstract

Common plastic goods, in general, and plastic shopping bags, that are generally made from polyethylene (PE), in particular, are a cause of considerable environmental nuisance. Development of a material that would degrade due to sunlight, in the open environment is, therefore, of considerable interest. In this study, for the first time ever, photocatalytic degradation of polyethylene, using titania nanoparticles, up to the maximum holding capacity of PE matrix (20% w/w), has been investigated under UV and visible light. The effect of water and air on the degradation of PE films was also studied. Materials were characterized using SEM, XRD, EDS, FTIR, TGA, Tensile Strength and Profilometry. Surface morphology of the exposed films was observed using light microscopy and Scanning Electron Microscopy (SEM). Formation of intermediate carbonyl species was investigated using the FTIR technique. It is conclusively demonstrated that the photocatalytic reaction rate constant was linearly dependent on the concentration of titania contained in the polymer matrix, with the degradation in the visible light about one-third slower than that under UV light. PE films containing 20% TNPs showed a maximum of 33% and 60% weight loss after 90 days exposed to visible light and UV light respectively. It was observed that highest weight loss of 21% was achieved when both air and water was available in the system. Presence of oxygen is very important for the initiation of degradation process however, the process cannot be sustained in the absence of moisture. The results of the study could be used to develop polyethylene films of the desired half-life, by changing the titania concentration.