Degradation of Polydimethylsiloxanes (Silicones) as Influenced by Clay Minerals

Abstract

To better understand the environmental fate of organopolysiloxanes (silicones), this study investigated the degradation of a 14C-labeled poly(dimethylsiloxane) (PDMS) on 12 Ca-saturated clay minerals. The rates and products of PDMS degradation were determined at 22 °C and 32% relative humidity, via sequential extraction and high-performance size exclusion chromatography (HPSEC). The results showed that all of the clays tested were catalysts for PDMS degradation. However, clay minerals varied substantially in their catalytic activity: kaolinite, beidellite, and nontronite were the most active; goethite and allophane were least active. In addition, PDMS degradation products bound more strongly to goethite and smectites. These results demonstrated that soil factors such as clay content and clay type are very important in determining the degradation rates of PDMS in soil.