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Committee Will Harmonize Weathering Tests in ASTM C24 Standards

Changes are being made to improve testing that determines the serviceability of building seals and sealants exposed outdoors.

ASTM Committee C24 on Building Seals and Sealants invites participation from the sealants and building community as it updates and harmonizes the weathering procedures in its standards.

“To evaluate the proposed revised parameters for the C24 standards in comparison with the existing parameters, and determine appropriate exposure durations, members of all C24 subcommittees have been asked to develop preliminary test data prior to the June 23-26, 2002, meetings of C24 in Salt Lake City,” said Norma D. Searle, Ph.D., a committee member who is leading the activity.

The committee hopes to bring uniformity to sealants testing. “Different types of sealants have been tested in different ways and they should not be,” said Searle, a consultant specializing in weathering and stabilization of polymeric materials from Deerfield Beach, Fla.

A draft resolution being considered by the C24 Executive Subcommittee calls for standards revisions according to these guidelines:

• Add xenon arc and fluorescent UV exposures to standards that do not include these exposures among the weathering tests;
• Specify test parameters for weathering according to the latest version of C 1442, Standard Practice for Conducting Tests on Sealants Using Artificial Weathering Apparatus. C 1442 will be referenced in all standards containing laboratory weathering test procedures;
• Base minimum exposure durations on the exposure required to produce measurable changes in least-acceptable products for their intended use;
• Specify exposure durations separately for each type of exposure, to obtain similar weathering effects on the same materials by the different types of exposures;
• Consider the validation of laboratory weathering tests by determining correlation with outdoor exposure based on relative stabilities of test materials, and type of changes produced;
• Obtain and archive data on acceleration factors for materials tested, to provide information for estimating service life by each type of laboratory-weathering test;
• Incorporate movement in test procedures for products when applicable.

Published in 1999, C 1442, Standard Practice for Conducting Tests on Sealants Using Artificial Weathering Apparatus, will be updated to reflect:

• Test parameters used for sealants by other organizations and in recently developed C24 Standards; and
• Test results in recent studies on sealants.
New or updated C24 standards containing laboratory-accelerated weathering tests have been issued by ASTM International:
C 1184-02, Standard Specification for Structural Silicone Sealants;
C 1519-02, Standard Practice for Evaluating Durability of Building Construction Sealants by Laboratory Accelerated Weathering Procedures;
C 1501-01, Standard Test Method for Color Stability of Building Construction Sealants as Determined by Laboratory Accelerated Weathering Procedures;
C 1523-02, Test Method for Determining Modulus, Tear and Adhesion Properties of Precured Elastomeric Joint Sealants; and
C 1518-02, Standard Specification for Precured Elastomeric Silicone Joint Sealants.

ASTM membership is not required to develop standards or provide test data. To participate in this activity, contact Norma D. Searle, Ph.D., Deerfield Beach, Fla. (phone: 954/480-8938). Committee C24 meets June 23-26 in Salt Lake City. For meeting or membership details, contact Scott Orthey, manager, ASTM Technical Committees (phone: 610-832-9730). //

Copyright 2002, ASTM