TiO 2 pigment structure and kinetics of PVC weathering

The influences of doping the core of TiO 2 pigments with Al 2 O 3 and of various inorganic surface modifications on the rate of poly(vinyl chloride) (PVC) weathering are investigated. The kinetics of loss of gloss are transformed into photooxidation rates by using Weibull statistics of failure, and a scheme of two consecutive reactions is fitted to the intermediate losses of brightness observed for the most photoactive pigments. When Ca/Zn stabilizers in PVC are exchanged for Pb stabilizers, gloss degradation rate doubles, and the energetic spread of irradiation defects broadens. No indications for specific interactions between pigment and stabilizer are found.