Nonequilibrium Lattice Fluid Model Research Articles

Gas Sorption and Dilation in Poly(2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene): Comparison of Experimental Data with Predictions of the Nonequilibrium Lattice Fluid Model

The sorption and dilation properties of a series of n-alkanes and the corresponding perfluorinated compounds have been examined in two amorphous copolymers of tetrafluoroethylene (TFE) and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole (BDD), commercially available under the names Teflon AF1600 and AF2400. The analysis was made at three different temperatures: 25, 35, and 45 °C, to test the effect of temperature on solubility and to evaluate the sorption enthalpies. The partial molar volumes of most penetrants have also been determined in both copolymers. The experimental data have been satisfactorily compared with the sorption isotherms predicted or correlated using the nonequilibrium lattice fluid model.

Solubility in Glassy Polymers: Correlations through the Nonequilibrium Lattice Fluid Model

The representation of solubility isotherms of gases and vapors in glassy polymers has been analyzed through the use of a thermodynamic model, nonequilibrium lattice fluid, recently introduced. The possible use of the model as a predictive tool for gas solubility in glassy polymers has been discussed in previous works for the special cases in which the polymer density in pseudo-equilibrium conditions is known from experimental measurements. In this paper, a different use of the model is presented in which the polymer density at different sorption conditions is not known from direct experimental measurements and is thus treated as a correlation parameter, following the typical linear dilation isotherm. The solubility isotherms thus obtained by the model have been compared with several experimental data, obtaining a rather satisfactory representation of the sorption isotherms, through use of two fitting parameters, at most.