An IPN membrane of hydrophilic polyurethane and hydrophobic polystyrene was prepared by the simultaneous polymerization method.
The pervaporation of water-ethanol, water-acetic acid and benzene-cyclohexane mixture was carried out and the permselectivity was investigated to evaluate the effect of hydrophilicity of the membranes and the feed composition.
The swelling ratio and the pervaporation rate of water-ethanol mixture showed a broad maximum at around 80 wt.% ethanol concentration. The swelling ratio and the pervaporation rate of benzene-cyclohexane mixture decreased monotonically with increasing cyclohexane concentration in the feed. In all ranges of feed concentration, water and benzene permeated preferentially through PU/PS IPN membranes.
It was found that the PU domain functioned as permeating pathways for water. It was also found that the swelling of the membranes by one or both component of the mixture and the difference in molecular size were important in influencing the selectivity.
The microseparated structure of hydrophilic-hydrophobic membrane was found to enhance the selectivity and the mechanical properties.
