Effect of Strain on the Modulus of Sealants Exposed to the Outdoors
Christopher C. White, Donald L. Hunston, Kar T. Tan
The effects of applied strain on sealants exposed to outdoor weathering were examined for two sealant formulations, sealants A and C. Both static and dynamic strain was applied to the sealants during the summer in a Gaithersburg, MD-outdoor location. Both sealants exhibited a reversible change in equilibrium distance. Stress relaxation studies on all samples revealed that, for sealant A, two mechanisms affected modulus change; exposure without applied strain increased the modulus while additionally applied strain decreased the modulus. Only one mechanism that decreased the modulus was found for sealant C. A 7% dynamic strain and a 25% static strain were observed to produce equivalent modulus changes in both systems.