ABERDEEN PROVING GROUND, Md. (Feb. 6, 2015) -- Scientists at the U.S. Army Edgewood Chemical Biological Center are making strides in understanding what happens to materials when they are contaminated with chemical warfare agents.
Recent ECBC work has enabled visualization and measurement of agent penetration into the subsurface depth of paints such as Chemical Agent Resistant Coating using scanning electron microscopy and energy dispersive spectroscopy.
"We are interested in learning how to decontaminate materials, but first, we need to understand where the agent goes inside of materials," said Dr. Brent Mantooth, a research chemist with ECBC's Decontamination Sciences Branch. "We couple modeling with experimental techniques to understand how the agent gets inside materials so that we can formulate decontaminants to get the agent back out." Funded by the Defense Threat Reduction Agency, researchers at ECBC have been developing techniques to answer these questions.
Many coatings on military hardware, like paint, are susceptible to chemical penetration, so scientists are interested in what happens when they are contaminated or decontaminated. The first step is to determine how certain characteristics of the paint influence how different chemicals seep into different paint types. In order to do so, Mantooth and members of ECBC's Decontamination Sciences Branch, designed an innovative method to investigate fundamental mechanisms of mass transport in coatings and thin films.
"What people might not realize is that some CWA can penetrate into various paints that are used in Warfighter equipment, and when these CWAs come back out, it can result in exposures to the Warfighter. This technique enables us to determine where the agents are in the material and to learn about the transport processes that resulted in the penetration," Mantooth said.
To prepare contaminated paint samples for a variety of military paints systems, the scientists applied liquid CWA to sample surfaces. Then, after the CWA soaked into the paint for a fixed contamination time, they cleaved the sample in half to expose a cross section of the interior. SEM-EDS was then used to measure the distribution of the CWA within the sample to determine how the CWA penetrated into the paint. Probing the samples with SEM-EDS allowed scientists to examine the topographical, spectral, and elemental mapping of the contaminant-material systems down to one-millionth of a meter.
"This technique enables imaging of the cross sections of the paint and measurement of the concentration of the various elements through the depth of the material," said Kayla Cooley, a materials physicist (OptiMetrics, Inc.) on the Decontamination Sciences Branch.
One of the challenges is that the scientists wanted to work with live CWA rather than simulants, so the instrument had to be modified for operation in a chemical fume hood. This use of SEM-EDS was the first time this type of equipment has ever been used with live agent work.
Data produced by SEM-EDS depict the CWA migration into the paint's top coat and primer layers depending on the time associated with contamination event. Based on their research, the scientists were able to see a correlation between agents and different paint components in terms of what properties and features were most influential in allowing or preventing agent to infuse the interior of the paint. This critical step allows researchers to begin to explore various decontamination methods, and to also uncover whether different paint compounds that are more resistive to CWA penetration could be used while still meeting all of the other military material requirements. The Decontamination Sciences Branch actively works with the Army Research Laboratory to study new paint formulations using the results of this work.
The team's research of the distributions of CWA in Coatings was published in American Chemical Sciences Applied Materials & Interfaces Journal in August 2014 (Vol 6, issue 18, pp 16289--16296). Mantooth and coworkers also presented their findings at the 2014 American Chemistry Society Conference.
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The Edgewood Chemical Biological Center is part of the U.S. Army Research, Development and Engineering Command, which has the mission to develop technology and engineering solutions for America's Soldiers.
RDECOM is a major subordinate command of the U.S. Army Materiel Command. AMC is the Army's premier provider of materiel readiness--technology, acquisition support, materiel development, logistics power projection and sustainment--to the total force, across the spectrum of joint military operations. If a Soldier shoots it, drives it, flies it, wears it, eats it or communicates with it, AMC provides it.
Related Links:
Research Article: Direct Measurement of Chemical Distributions in Heterogeneous Coatings
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