Forging the chain: destroying chemical warfare agents by polymerization

Courtesy Photo | Image associated with article in December JSTO in the News: Forging the chain: destroying chemical warfare agents by polymerization  

FORT BELVOIR, VA, UNITED STATES

01.30.2020

Courtesy Story

Defense Threat Reduction Agency's Chemical and Biological Technologies Department

What if a chemical warfare agent (CWA) could be safely neutralized (destroyed) in less time and with less resources and personnel than what is currently needed today? The Defense Threat Reduction Agency’s Chemical and Biological Technologies Department (DTRA CB) is developing a one-step, less resource-intensive, and portable capability that applies the chemistry of polymerization to neutralize CWAs. This capability will allow warfighters to destroy CWAs without the need for sophisticated equipment, resources, power generators, or voluminous quantities of neutralizing materials. Warfighters will be able to carry neutralizing chemicals onto the battlefield, and the new method is easier to perform than current methods; more warfighters within a tactical unit will be capable of destroying cached CWAs.

Current destruction methods are incineration and chemical neutralization; both are multistep processes that require large, powered equipment that can only be operated by highly trained personnel. Chemical neutralization also necessitates large volumes of chemical decontaminants and water, which are beyond the transport capability of a warfighter tactical unit.

The goal of chemical neutralization is to change the chemical composition of a CWA to reduce its toxicity and prevent its use as a weapon. Current neutralization methods employ other chemicals to break a CWA’s chemical bonds through hydrolysis or oxidation. Hydrolysis and oxidation rely on chemical stoichiometry, which specifies the ratio of reactant molecules necessary to sustain a chemical reaction. Hydrolysis or oxidation requires at least one molecule of water or oxidizer, respectively, for every molecule of CWA that needs to be neutralized. The quantity of CWA dictates the amount of oxidizer or water needed for neutralization. Ideally, the mass of neutralizing chemicals should be as small as possible (less than 10% of the CWA mass). A polymerization strategy may meet this challenge.

Polymerization is the linking of single molecules (monomers) into a chain of molecules (a polymer). For example, a can of liquid paint contains binding agents that are activated when the paint interacts with air and polymerizes it into a solid coat of color. The goal of CWA polymerization is to develop a similar reactive process that is more efficient than hydrolysis or oxidation and also less dependent on stoichiometry. Polymerization would require only small amounts of chemicals and water — amounts that a warfighter tactical unit would typically possess — to form long polymers of CWA molecules.

With funding from DTRA CB, researchers at the U.S. Army Combat Capabilities Development Command Chemical Biological Center and Sandia National Laboratories seek to develop a polymerization method that reduces the toxicity of a CWA by 90% and, additionally, changes the CWA from a liquid to solid (a phase-state change) so that it has no potential for use as a weapon In laboratory tests to neutralize a nerve agent, a type of CWA, researchers achieved a complete phase-state change at room temperature in less than 13 days. Even if an enemy were to come across the stored CWA within a week after a polymerization was initiated, the half-neutralized CWA would be well on its way to changing its phase state and, therefore, not usable as a weapon.

Researchers continue to study the efficacy of polymerization as a neutralization method. They seek to develop a method that irreversibly polymerizes CWAs and causes them to solidify inside the original container, thereby eliminating any hazard to warfighters. Before polymerization is ready for use by a warfighter tactical unit, researchers must further understand the method’s chemical reaction rates, molecular processes by which these reactions occur, definitive composition of the neutralized compound, and toxicity of the neutralized product. For example, the polymerizing chemicals may cause the CWAs to overheat, posing the danger of some CWAs vaporizing, which then harms warfighters, so researchers are exploring ways to minimize the potential for overheating. Additionally, the rate of reaction cannot be too fast, or the polymerization will not cause every CWA molecule to neutralize, thus resulting in a mixture of neutralized and still-toxic CWAs. To limit the speed of the reaction, researchers have developed novel, reactive chemical pellets that dissolve slowly to neutralize the CWA.

Researchers are also exploring “self-mixing” reactive processes, which are enabled by the effervescence (or microbubbling) created by the ingredients coming together, so that a tactical unit can initiate the neutralization and move on. The self-mixing is gentle and promotes a thorough reaction between each molecule of CWA and the polymerizing chemical. The more thorough the mixing, the more complete the neutralization. Researchers are using nuclear magnetic resonance spectroscopy to monitor the polymerization reaction and identify the resulting compounds and their toxicity.

Polymerization shows promise as a one-step method that will allow warfighters to efficiently initiate the destruction of stored CWAs and proceed to another mission, knowing that once the chemical reaction starts, it will continue until the CWA is no longer a weapon.

POC: Glenn Lawson, Ph.D; [e-mail]

• Date Taken: 01.30.2020
• Date Posted: 01.30.2020 15:32
• Story ID: 361087
• Location: FORT BELVOIR, VA, US