Permeation of Solvent Mixtures Through Protective Clothing Elastomers

Permeation through protective clothing is envisioned as a process involving solution of a chemical challenge into the elastomer and diffusion within the elastomer matrix.

The diffusion process is modeled using Fick's Laws, and steady-state permeation experiments are used to determine a proportionality constant, the permeation coefficient. This permeation coefficient includes both a solubility factor and a diffusion factor, and has been successfully used to characterize permeation rates.

In order to predict permeation resistance, researchers have focused on the solution step of the process. Models employing solubility parameters, such as Hildebrand's solubility parameter and Hansen's 3-dimensional solubility parameter have been employed with some success to predict both breakthrough time and permeation rate for specific elastomer-challenge combinations.

Mixtures of solvents are also characterized by solubility parameters, intermediate between the parameters of the individual components. Examination of limited mixture permeation data indicates that solubility parameter models can be extended to predict some aspects of permeation behavior.

Theory and work from other fields indicates that other aspects of permeation behavior, particularly those related to molecular kinetics may require alterations of the solubility parameter models. These aspects will be discussed.