The effect of UV radiation on a family of low density polyethylene films containing different concentrations of TiO2 nanoparticles has been studied. The photodegradation was monitored using FTIR measurements of carbonyl group development and an in situ FTIR method that tracks the generation of CO2 as a principal product of degradation. Samples containing dispersant and/or a phenolic antioxidant but free from TiO2 particles were examined as controls. It was shown that the effects of photodegradation of the polymers could be followed even when these additives were present. The dispersant gave rise to absorption in the carbonyl region of the IR spectrum but meaningful results concerning the progress of photodegradation were obtained using difference spectra. Good correlation was found between the carbonyl and the CO2 measurements of the relative photosensitivities of the films with different compositions, and both methods indicated that addition of the nano-particulate rutile TiO2 had decreased the film photostability. The decreased photostability inferred from spectroscopic measurements was also observed as a reduction, from similar to 1100 h to 400 h, of the exposure time before film cracking, when samples were exposed to UVA radiation in QUV equipment. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 13301338, 2011