Physical weathering is usually responsible for the degradation of maxillofacial prosthetic elastomers and the replacement of prostheses. The purpose of this study was to investigate the effects of outdoor weathering on the physical properties of four nonpigmented facial prosthetics after 1 year of exposure. In addition, simple mathematical models were developed to correlate the measured properties with irradiation time, including parameters with physical meaning. Three different medical-grade polydimethyl siloxanes (PDMSs) and an experimental chlorinated polyethylene (CPE) were examined in this study. The samples were exposed to solar radiation for 1 year in Athens, Greece. Mechanical tests (compression and tensile) were performed using universal-type testing machine, and hardness measurements were performed with a durometer (Shore A). Thermal tests were also performed with a differential scanning calorimeter. Simple mathematical models were developed to describe the examined properties. Changes observed in the properties of examined materials, before and after the exposure, reflected the effect of weathering. More specifically, two of the silicone prosthetics (Elastomer 42, TechSIL 25) seemed to become harder and more brittle, different from the other silicone (M511) sample and the CPE sample, which became softer and more ductile. Moreover mathematical models correlate the measured properties with irradiation time, and their constants indicate that duration of exposure seems to increase the degradation. Significant changes in the mechanical and thermal properties of the examined materials were observed as a result of outdoor weathering. The effect of weathering on samples' properties was introduced through its effect on the mathematical models' parameters.

A Fe-doped titanium dioxide (Fe-TiO 2 ) was prepared using hydrothermal method and used for degradation of phenol from aqueous solution. The samples were characterized by X-ray diffraction (XRD) and showed a presence of both TiO 2 and Fe 2 O 3 peaks. The photocatalytic activity of Fe-TiO 2 catalyst was evaluated for oxidation of phenol in aqueous solution using different illumination sources. Visible light irradiation from sun, UV light sources with 190 and 390 nm, fluorescence and dark environment were used and found that the degradation of phenol was in the order of 7.8%, 12%, 7.5%, 6.8% and 5% obtained after 24 h, respectively. It was found that the increase in exposure time to UV, the increase in solution temperature and pH have increased the rate of phenol degradation in solution. This rate was best fitted using first order kinetic model with reaction constant of 3 10 268 . 6 − × .