Evaporation and Degradation of a Sessile Droplet of VX on an Impermeable Surface
Technical Report,01 Oct 2014,30 Sep 2016
EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND United States
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This report highlights experimental studies into the combined physical and chemical processes that occur when a sessile droplet of 2-diisopropylaminoethyl-O-ethyl methylphosphonothioate VX evaporates from an impermeable surface at elevated temperature. Specifically, when the VX droplet is in atmospheric conditions at elevated temperatures 40 C, degradation of VX occurs via an established autocatalytic mechanism. The resulting chemical change causes a corresponding change in the contact angle and evaporation rate of the sessile droplet on an impermeable surface. Comparison to the evaporation rate and contact angles of known degradation byproducts suggests that phase separation of hydrophilic ethyl methylphosphonic acid and VX-pyro and hydrophobic VX-disulfide components occurs. The hydrophilic components make up the core of the droplet and the hydrophobic component comprises the shell. Continuum models of the process suggest that experimental observations cannot be reproduced without accounting for phase separation.
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