For LDPE/TiO2 nanocomposites, the photodegradation mainly happens on the LDPE film surface where electrons or holes combine with adsorbed oxygen molecules or hydroxyl ion to produce O2‾ or HO•, two very important reactive oxygen species for a new and useful way to decompose solid polymer. In this paper, solid-phase photocatalytic oxidation of LDPE with TiO2 nanoparticles as photocatalyst under artificial light irradiation was investigated. LDPE 150E - Dow Chemical was used as polymer matrix and Degussa P25 as TiO2 photocatalitic nanoparticles. Low density polyethylene nanocomposites with 1 to 4 wt% nano-TiO2 filler were prepared by direct mixing in the Brabender Plasti-Corder mixer chamber. The samples used for thermal, mechanical and optical characterizations – square plates 150×150×0.30mm – were prepared by compression molding in an electrically heated press at 170ºC for 5 min, with a force of 50 kN. Morphological, thermal, mechanical and optical changes in polyethylene nanocomposites as a result of TiO2 nanofiller were investigated by FT-IR spectroscopy, polarized optical microscopy (POM), Thermogravimetric and dynamic mechanical analysis. LDPE-TiO2 composite films were exposed to light irradiation under natural and simulated conditions of solar light in a Xenotest apparatus and the effect of ageing was evaluated. Influence of ageing on thermo-mechanical properties of composite materials and structural modifications were investigated together in relationship with mechanisms of photodegradation. The photo-catalytic degradation of nanocomposites is significantly faster than the simple photolytic decomposition of pure LDPE, which goes on as more reactive oxygen species are generated and could be used as a solution for the destruction of polyethylene wastes. The notable change in the FT-IR spectra was intensification of carbonyl region along with the appearance of unsaturated groups due to photo-oxidation of the alkyl chains.