Novel Methodology for the Estimation of Chemical Warfare Agent Mass Transport Dynamics. Part II: Absorption

A novel experimental and computational methodology has been developed for estimating Fickian mass transport parameters of organic molecules through stagnant mediums such as air, paints, or polymeric substrates. Dynamic contact angle experiments were performed to measure the droplet volume evolution with the chemical warfare agent bis(2-chloroethyl) sulfide (distilled mustard, known as the chemical warfare agent HD) on military-relevant substrates. A finite element model for simultaneous evaporation and absorption was used to analyze the experimental data and determine the mass transport parameter values of the agent in the absorptive material. The computational model was validated by comparison with the results of a complementary experimental technique involving testing for HD vapor emission from the contaminated material. The model predicted HD vapor emission rates from a silicone elastomer substrate for contamination conditions not directly tested. The simulation results show that the model parameters can be used to provide an accurate prediction of the absorbed mass and concentration distribution in the substrate at a range of environmental temperatures (20 to 50 degrees C) and contamination times (0 to infinite min). Predicting the absorbed mass in various substrate types and environmental conditions enables an accurate prediction of the resulting hazards from contaminated materials.