STP1168: The Impact of Curing Conditions on the Appearance of Sealant Before and After Artificial Weathering

    Myers, JC
    Senior Staff Engineer and Associate, Simpson Gumpertz & Heger Inc., Consulting Engineers, Arlington, MA

    Nelson, PE
    Senior Staff Engineer and Associate, Simpson Gumpertz & Heger Inc., Consulting Engineers, Arlington, MA

    Pages: 13    Published: Jan 1992


    Abstract

    This paper presents our preliminary laboratory research to determine the effects of various moisture and temperature conditions during cure, and joint extension after cure, on the internal and external appearance of a two-part polyurethane sealant before and after artificial weathering. We examined the impact of these conditions on the development of voids within the sealant, softening or tackiness on the sealant, and crazing and splitting at the sealant surface. Improper mixing created most of the large internal voids. Application of sealant on a damp substrate produced foaming in the sealant at the bond surface. Contact with water during cure softened the sealant surface, but not the entire thickness of the sealant. Artificial weathering caused surface crazing, but combining artificial weathering and constant extension produced deep cracks and splits through the sealant, with the depth of cracking increasing with greater extension. We performed additional testing on other sealants, including some that are not two-part polyurethane, by artificially weathering them at a constant extension. The crazing and splitting with these other sealants varied with the particular brand of sealant from no crazing to through-splits.

    Keywords:

    crazing, splitting, voids, sealant deterioration, polyurethane sealant, silicone sealant, accelerated weathering


    Paper ID: STP24231S

    Committee/Subcommittee: C24.40

    DOI: 10.1520/STP24231S


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