Photocatalytic degradation of polypropylene film by dispersed titanium dioxide particles

Polypropylene (PP) film (thickness 44–47 μm) containing 0·25 wt% of titanium dioxide (TiO2) powder was photoirradiated for times up to 200 h at room temperature in air. Among the TiO2 powders used in this work, extrafine particles of P-25 TiO2 (Nippon Aerosil) alone led to the degradation of the film, as detected by change in color, whitening, and marked decrease in the elongation at break. Transmission electron microscopic measurement revealed that voids around the P-25 particles in the film were produced by TiO2-photocatalytic oxidation, causing the whitening and decrease of mechanical characteristics.