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Permeation and Diffusion

CT Associates has developed techniques to measure permeation rates of acid gases (e.g. HCl, HNO3 and HF), or solvents and oxidizers (e.g. O3). These can be done at various temperatures and/or concentrations to directly achieve application conditions, or even exceed them for durability-type testing. These evaluations are typically conducted on samples of films or tubing, but can also be conducted on components or even assemblies of interest. 

Vapor Pressure Visualization of HF (left) and HCl (right)

HF vapor pressure vs concentration and temperature
HCl vapor pressure vs concentration and temperature

These techniques have been used to measure the susceptibility of components, such as pumps and valves, to degradation by acid gas permeation. More importantly, they have been used to evaluate and compare materials to inform design choices in order to maximize lifetime in these harsh conditions. Additionally, models have been developed to predict the non-steady-state transport of gases and liquids through polymers or into other liquids. These can then be used to even predict component lifetime as a function of acid concentration and temperature. Check out our relevant publications HERE.

Permeation Coefficient of HCl Through Various Polymers

Permeation coefficients of HCl through various polymers

Model of Expected Relative Lifetime in HCl

relative expected lifetime of components used in HCl
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