Physical property changes in commercial structural silicone sealants due to weathering

The changes in physical properties of three different commercial silicone sealants used in structural glazing applications were monitored as a function of various environmental and climatic aging factors. These variables included, exposure to solar radiation(UV) and simulated rainfall in which the pH of the water ranged from 3 to 11. The extremes of the pH range represent recorded values for acid rain(pH=3) and basic cleaning solutions(pH=11), respectively. A second portion of the study involved contacting test coupons simultaneously with simulated rain and high levels of gaseous ozone. The experimental tensile tests coupons were cut from sheets of DC-790, DC-995 and DC-983. An Instron tester was used to measure the changes in engineering properties such as moduli and tensile strengths of the test samples as a function of time of exposure to the different variables. Unexposed samples, kept at ambient laboratory conditions, were used as the control.