The permeability, ideal separation factor, and the activation energy for permeation ($E_\bar{p}$) of oxygen and nitrogen through the IPN membranes of polyurethane/polystyrene were determined. The effect of synthesis temperature, crosslink density, and the composition of the IPn membranes were analyzed.
The membranes were prepared by the sequential polymerization method. Polyurethane was polymerized thermally and polystyrene was photopolymerized at various temperatures. As the synthesis temperature was decreased, IPN membranes showed the inwardly shifted two Tg's of the component polymers, decreased domain size, and increased density due to the increase of the degree of mixing.
The permeability coefficients were independent of pressure for all the IPN compositions. The magnitude of the activation energy for permeation increased with decreasing synthesis temperature and showed maximum values at 75wt% PU. As the crosslink density of the IPN membrane was increased, the permeability coefficient decreased. As the synthesis temperature was decreased, the permeability coefficient decreased and ideal separation factor increased. With compositional variation, the permeability coefficient reached minimum value and ideal separation factor reached maximum value at about 40wt% PU. Above permeability data agreed quite well with the simple free volume model.
