Permeation of gases in polymers: parameter identification and nonlinear regression analysis

In numerous previous studies it has been shown that the permeability of gases in polymers depends strongly on the polymer structure, on the gas type, as well as on the conditions of temperature and pressure. The theoretical models that have been proposed and developed in the literature, describe the transport mechanism of molecular species in polymers by diffusion involving a concentration-dependent diffusion coefficient. However, the exact form of this dependency and exact information on the diffusion coefficient and on the solubility coefficient are not always available in the literature, in particular in extreme conditions like in the case of protective polymer coatings for flexible offshore pipes where the temperature and pressure of the diffusing gas can be very high.