Technique for Monitoring Environmentally Induced Changes in Polymer Sealants
Dr. Donald Hunston, National Institute of Standards and Technology
Dr. Christopher White, National Institute of Standards and Technology

March 24, 2010
10:00-11:00 a.m. ET
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Course Description
Sealants are an essential component in modern construction since they prevent moisture intrusion which is a major source of damage.   Mechanical properties are important for the performance of a sealant since it must accommodate the expansions and contractions that weather produces in the structure.  Characterizing the mechanical properties of sealants is complex because they are non-linear viscoelastic materials.  This presentation describes a technique based on stress relaxation tests which has been shown to be an effective characterization method for a wide range of samples.  This procedure also provides a useful way to monitor changes in the behavior of a sealant exposed to environmental aging.  The original method, however, does not distinguish between molecular level changes like a decrease in effective crosslink density and macroscopic effects like cracking and debonding.  Consequently, a modified procedure is being developed utilizing both tension and compression testing which shows considerable promise for characterizing both molecular and macroscopic changes.  Both the theoretical basis for this method and some initial examples that show successful application of the technique will be presented. 

 

Who Should Attend?
This webinar is designed for anyone who wants to learn more about sealant, learn how to quantify the effects of weather on a sealant, and use of stress strain response of the sealant to monitor changes due to the weather will be discussed.

 

About the Speakers:

Donald Hunston is an independent consultant (Hunston Scientific) and a part time Guest Scientist in the Materials and Structures Research Division, National Institute of Standards & Technology.  He has over 30 year of experience with mechanical properties of composites, structural adhesives, sealants, coatings and other polymeric systems.  From 1980 to 2001, he was in the Polymers Division at NIST where he served as Acting Deputy Chief from 1998 to 1999 and Leader of the Polymer Composites Group between 1983 and 1996.  He developed and directed NIST's program on Polymer Composite Materials which was the government’s largest in-house research effort devoted to commercial applications of composites.  It focused on lowering costs through advances in processing science and understanding durability issues.  He has worked in NIST’s Advanced Technology Program Office and the Advanced Manufacturing Board in DARPA=s Technology Reinvestment Program.  Between 1971 and 1980, he was in the Chemistry Division of the Naval Research Laboratory where is duties included acting- Acting Head of Adhesives and Composites Section between 1978 and 1980.  He research has produced over 400 talks and more than 260 papers in the scientific literature. 

Christopher White joined NIST in 1997 as a National Research Council Postdoctoral Research Associate. In his present position as a research chemist, Dr. White is involved in a number of exciting projects related to developing metrology for service life prediction of organic materials. Dr. White is leading a team of dedicated researchers who are investigating the role of acceleration on the degradation of elastomeric materials, for example building sealants. Dr. White is a expert in understanding how the complicated mix of rheology, thermal transport, and moisture diffusion affects the adhesive and cohesive failure of these materials. This state of the art research will result in significant progress in assessing and predicting the durability of these materials.

Prior to joining NIST, Dr. White was honored by receiving a University of Connecticut/Institute of Materials Science Post-doctoral fellowship where he worked on the specific interactions between extender and matrix and the affects on the rheology of recycled plastic materials. Dr. White was awarded a Ph.D. from the University of Wisconsin in 1994. He has received many awards such as the prestigious E.I. Dupont Rheology Award in 1994. He has published numerous peer reviewed papers and conference proceedings. He has served as a reviewer for numerous journals including: Journal of Rheology, Journal of Polymer Science, Part B Polymer Physics, Journal of Engineering Materials Science and Technology, Journal of Polymer Science and Engineering. He has been asked to sit on review panels for the National Science Foundation, the Society of Plastics Engineers, and NSF/NIST/Surf Program. He has served as an elected officer in several professional societies. He has served as the Technical Program Chair for several national conferences related to rheology.

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