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Physical property changes for two structural silicone rubber sealants were studied to determine the effects of expected variations in environmental temperature and moisture. Test coupons were subjected to uniaxial tensile forces at different isotherms and moisture levels. The elastic modulus at zero strain, stress at a function of extension, and relaxation times were determined for the two sealants.
For extensions of zero to thirty percent, and for temperatures over a range of 0°C to 30°C, both sealants were found to behave as ideal elastomers. The use of the model for an ideal rubber allowed the cross link density, tensile modulus, and stress to be quantified for a given isotherm. Normal, environmental temperature variations did not compromise sealant performance.
Moisture (immersion in water) appeared to have little effect on the measured mechanical properties. The pH of the water over a range of 5 to 12 also appeared not to affect sealant performance. However, strong sulfuric acid solutions (pH < 2.0) seriously compromised the integrity of both materials.
Silicone rubber sealants, viscoelastic, thermal changes, crosslinking, acid rain
professor of Chemical Engineering, Texas Tech University, Lubbock, Texas