SYMPOSIA PAPER Published: 01 January 1994

The Relation Between Rheology, Artificial Weathering, and Urethane Sealant Performance


There has been vigorous debate on the ability of urethane sealants to withstand the conditions found in high-performance construction applications. A number of studies have suggested that multicomponent urethanes, as a generic technology, are unable to endure the high heat, humidity and ultraviolet light found in some parts of the world.

This paper argues that it is incorrect to make blanket statements about the performance characteristics of any sealant technology, whether it is silicone or organic. The focus is, however, on multicomponent urethanes. Results of standard ASTM xenon and QUV tests are discussed. Several novel test regimens, including the “frog pond test” and sophisticated Theological techniques, are also reviewed. To gather as much data as possible, samples were run through these procedures for as long as 7000 hours.

This paper outlines several important conclusions. First, silicones actually have a higher modulus at cold temperatures (below -35°C) than the multicomponent urethanes examined. Second, the wide range of performance results in the urethanes tested highlights the fallacy of blanket statements about these sealants. Some were clearly unable to endure the conditions to which they were exposed. Other multicomponents, however, did not degrade. Rheological techniques are used to augment the data provided by the traditional QUV and xenon procedures.

Author Information

Leonard, NE
Tremco, Inc., Sealants and Coatings, Beachwood, OH
Malik, TM
Tremco, Inc., Sealants and Coatings, Beachwood, OH
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Developed by Committee: C24
Pages: 21–32
DOI: 10.1520/STP13997S
ISBN-EB: 978-0-8031-5289-2
ISBN-13: 978-0-8031-1993-2