Effects of bismuth vandate and anthraquinone dye on the photodegradation of polycarbonate

Both inorganic and organic compounds, such as oxides or salts of metals and polycyclic and azo compounds, are frequently used as colorants in polymeric systems. Bismuth vanadate pigment has been used as an environmentally friendly alternative for cadmium containing pigments and anthraquinone dyes represent a polycyclic colorant class of wide use in polymers. Besides their coloring properties, both bismuth vanadate and anthraquinone present photocatalytic activity or photochemical properties that can influence the mechanism and the kinetics of the photodegradation of the polymer into which they are incorporated. In this paper the influence of bismuth vanadate pigment and anthraquinone dye on the photodegradation of polycarbonate was evaluated. For this purpose, samples of polycarbonate containing the colorants were submitted to photochemical aging following the recommendations of ASTM G53. Bismuth vanadate accelerates the photodegradation of polycarbonate, causing a faster drop in the mechanical properties and an increase in the hydroperoxide concentration during the aging process. The coloring ability of the pigment is also affected. The photodegradation behavior of polycarbonate in presence of bismuth vanadate may be caused by a possible direct chemical reaction between pigment and polymer, promoted by UV radiation. On the other hand, the presence of anthraquinone dye seems to stabilize the polycarbonate against photodegradation through a deactivation mechanism of the excited state