1. Material permeability

1.1 Theory

At a given temperature, the transport of a gas molecule through a homogeneous (non-porous) membrane can be described as a 3-step process (if we neglect the formation of boundary layers):

• condensation and solution of the penetrant on the face corresponding to the highest partial pressure of the gas in question (upstream face);

• gas diffusion through the polymer membrane, due to the concentration gradient (chemical potential);

• evaporation on the downstream side.

Thus, the permeability P to the gas under consideration is the product of a kinetic parameter, the diffusion coefficient D (m ² ...