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The objective of this study is to identify criteria for the selection of laboratory equipment for weathering studies of sealants that allow improvements in the correlation of accelerated weathering results with outdoor exposure results.
The Approach of the study is to compare physical-chemical characteristics of sealants, which were exposed to various laboratory methods and outdoors. Polyurethane, silicone, polysulfide, and Kraton®-based sealants were selected for this study. Sealants were exposed outdoors to wet (Florida) and dry (Arizona) climatic conditions. The laboratory studies were conducted in a fully equipped xenon-arc weather-ometer simulating wet climate conditions, a xenon-arc tabletop device, simulating dry climatic conditions, and a fluorescent UV condensation weathering device.
The degradation of the sealant surface on exposure to both natural and laboratory conditions was compared on the basis of morphological changes. The following methods were used to study chemical and morphological changes: TGA, DSC, polarized light microscopy, and image analysis. The results of physical-chemical studies are related to the esthetic performance of sealants measured by an image analysis to determine the rate of crack formation and the development of characteristic morphological features of crack formation in different sealants.
In this analysis, the exposure to natural conditions is used as the point of reference. The physical-chemical changes due to weathering in laboratory devices are compared with outdoor exposure results to verify similarity of the failure morphology. A valid laboratory weathering procedure is expected to result in the same degradation mechanism and induce similar modes of failure as outdoor weathering.
sealant, weathering, image analysis, morphology, microscopy, DSC, TGA
Project Manager, ChemTec Laboratories, Inc., Toronto, Ontario
Associate Professor, Technical University of Lodz, Lodz,
Weathering Instrumentation Manager, Atlas Electric Devices Company, Chicago, Illinois