Standardization News

Sealant manufacturers will use a new ASTM International standard to evaluate new products and changes to these products due to exposure to weather. The new standard, C1735, Test Method for Measuring the Time Dependent Modulus of Sealants Using Stress Relaxation, is under the jurisdiction of Subcommittee C24.20 on General Test Methods, part of ASTM International Committee C24 on Building Seals and Sealants.

"Sealant is such an attractive and useful material for separating the inside from the outside in the building envelope because of its unique attributes such as elasticity, adhesion and barrier properties," says Christopher White, Ph.D., research chemist, National Institute of Standards and Technology, and a C24 member. "Changes to these properties indicate changes to the molecular structure that often precede failure. This standard, using commonly available laboratory equipment, allows manufacturers to directly measure the properties that are of real interest."

White notes that new sealant is often firm, soft and pliable and can be stretched without breaking while old sealant can be hard, cracked, brittle and sometimes almost like liquid.

"C1735 quantifies the properties of interest that can be used to follow those changes in the sealant, resulting in early detection and correction of problems to sealant properties," says White. "Previous to this standard, you had to rely on visual inspection of the sealant."

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CONTACT Technical Information: Christopher C. White, Ph.D., National Institute of Standards and Technology • Gaithersburg, Md. • Phone: 301-975-6016 O ASTM Staff: Stephen Mawn • Phone: 610-832-9726 O Upcoming Meeting: Jan. 8-10 • Ft. Lauderdale, Fla.