Approaches for predicting the permeation resistance of chemical protective clothing polymers were investigated and assessed for accuracy and applicability to the Premanufacture Notification (PMN) review process of the U.S. Environmental Protection Agency (EPA) Office of Toxic Substances (OTS). The approaches emphasize the prediction of cumulative permeation and include: (1) a predictive model based on Fickian diffusion theory and (2) test methods for directly assessing permeation resistance.
The predictive model is based on refinements of existing theoretical approaches for estimating diffusion coefficients and solubilities from the physical properties of the solute and polymer. Permeation model predictions were compared to well-documented permeation data from the literature. Examples of the model's range of applicability and its limitations are provided. Although the results of the permeation modeling approach are promising, direct testing is the most accurate approach to assess clothing performance for the variety and complexity of chemicals and chemical mixtures that are typical of PMN substances. Consequently, chemical resistance test methods were reviewed for accuracy and applicability. Test methods reviewed include permeation tests, degradation tests, liquid immersion weight change tests, and sorption/desorption methods. Based on this review, a hierarchy is proposed that ranks chemical resistance tests according to their ability to generate data needed to assess PMN clothing requirements.