Long term natural ageing of silicone elastomers

Ten different silicone elastomers have been exposed in Australia to hot-wet, hot-dry and temperate environments for 20 years, with earlier withdrawals of specimens after 2, 5 and 10 years. In addition, specimens were buried in the soil for two years in the hot-wet and hot-dry environments and specimens were also immersed in tropical seawater for two years. In general, the specimens, which covered the range of silicone elastomers available 20 years ago, survived the natural ageing conditions very well. Bent loop specimens of most of the elastomers were still intact and uncracked after 20 years temperate exposure, however rodent attack at the hot-wet jungle site caused considerable damage to the bent loop specimens in that environment. The changes in mechanical properties of the specimens exposed for 2, 5, 10 and 20 years can be analysed according to polymer type and severity of exposure conditions to yield valuable information on the most suitable materials for long term outdoor applications.