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The modulus of a silicone sealant elastomer is one of the most fundamental properties of these materials that can be measured on a routine basis. It is also a very complex function of several variables. These variables include the chemistry of the silicone polymer and the type of filler compounded into the product. Moreover, once the sealant is placed into service, additional variables such as loading and displacement history, time-temperature cycles, and weathering exposure become significant. Several approaches have been developed to monitor and characterize changes observed in three specific commercial silicone sealants. While silicone polymerization chemistry determines the broad characteristics of these sealants, it was observed that filler type, particulate bulk and cohesive material performance, and weathering can also contribute long term effects. These effects on some of the engineering properties pertaining to silicone elastomers used in building sealant application is the subject of this paper. Elastomers exhibit compressive moduli that can be several times that of the tensile moduli. In addition, acid and base pH levels from exposure to precipitation can accelerate residual cross-linking and ultimately lead to sealant degradation. The net result produced by such experiments has been a better understanding of sealant properties.
structural silicone sealants, modulus, fillers, weathering, aging, tensile strength
Professor, Texas Tech University, Lubbock, TX
Research Associate, Texas Tech University, Lubbock, TX