In interesting dual presentations, John Greenzweig of H.B. Fuller discussed not only the applications for desiccants and sealants, but also the chemistry. In his first presentation for the 2012 Insulating Glass Manufacturers Alliance (IGMA) Educational Seminar, “Desiccants/Desiccated Matrix,” Greenzweig explained desiccant adsorption.

According to Greenzweig, “the primary role of the desiccant is to adsorb moisture over time.”

“Adsorption is a phenomenon that takes place as the airspace cools; desorption takes place as it heats up,” Greenzweig stated simply. “As moisture is adsorbed by the molecular sieve, the capacity of gas adsorption/desorption is reduced.”

Greenzweig noted that desiccant matrices, which typically are applied as a hotmelt, have a slower adsorption rate than beaded desiccant and therefore have a slower frost point depression speed and “allow for slower moisture pick-up during the IG (insulating glass) manufacturing process.”

In his second presentation, “Sealants,” Greenzweig offered a chemical background of the many available sealants, which include “silicones, urethanes, butyls, polysulfides and other polymer types.” He said “the primary purpose [of sealants] is to prevent environmental elements from entering the structure, exiting the structure and permitting movement of the substrates.”

Greenzweig went on to discuss the chemical variations between the different sealants and how those differences affect the cure and cohesion.

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