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The Waterborne Symposium

Environmentally Friendly Coating Technologies

Mission Statement:

To administer the preeminent educational/technical forum in the United States directed to the science and technology of surface coatings and  to provide revenue to support and advance the School of Polymers and High Performance Materials at The University of Southern Mississippi.


Sarah Cotts - Measuring Rheological and Mechanical Properties of Waterborne Coatings During Drying Under Controlled Relative Humidity

Sarah Cotts.png
Sarah Cotts.png

Sarah Cotts - Measuring Rheological and Mechanical Properties of Waterborne Coatings During Drying Under Controlled Relative Humidity


Sarah Cotts
Applications Scientist
TA Instruments
(302) 588-3795
Co-authors: Aly Franck, Ph. D; Tianhong Chen, Ph. D


Sarah Cotts has a B.S in Polymer Chemistry from the College of William and Mary.  For 3 years she worked for Sartomer Company as an Applications Scientist, developing UV curable formulations for a variety of applications including inks, wood coatings, anti-corrosion coating and adhesives.  She currently works for TA Instruments as a Rheology Applications Scientist, supporting rheology and dynamic mechanical analysis users in all fields. 


Shear rheology has long been used to characterize flow properties of waterborne coatings.  However, traditional rheological measurements do not adequately characterize the development of mechanical properties during drying.  This is due to the inherent limitations of parallel plate or cone and plate testing fixtures, which do not expose the coating surface to the environment and prevent evaporation.  In parallel plates, the drying process is limited by the rate of diffusion from the center of the plate to the outer edge.  

In this study, novel testing geometries are used to measure changes in viscoelastic properties of waterborne coatings during drying.  While traditional parallel plates prevent the majority of sample from drying, these open geometries allow evaporation to occur more readily.  Unlike existing methods to study rheological changes during drying, which rely on measuring relative changes of a coating on a substrate, this technique provides a quantitative measurement of viscoelastic properties.  

The measurements presented here are performed under controlled relative humidity and temperature, to evaluate the environmental effects on drying time.  In addition, the environment may affect the physical properties of the dried coating.  This study also presents dynamic mechanical analysis (DMA) of finished coatings, as a function of temperature and relative humidity.   This testing capability allows for improved understanding of the effects of adsorbed moisture on the physical properties of waterborne coatings in their end use. 

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