THE INFLUENCE OF POLYVINYLPYRROLIDONE (PVP) IN POLYETHERIMID PVP BLEND MEMBRANES UPON VAPOR SEPARATION/

Polyetherimide/polyvinylpyrrolidone (PEI/PVP) blend membranes were pre pared by adding PVP to a PEI casting solution in the range 5-30%. An e ffect of the added polymer upon selectivity could not be observed when non-condensable gases were applied. Yet, the influence of the PVP upo n the membranes' separation capability was obvious when a toluene/meth ane mixture was used. At 5% PVP the selectivity with respect to toluen e reaches a value of 1000 that remains unaltered up to 200 h. Besides the percentage of the PVP in the blend membrane also its molar mass ha s to be considered. Lower molar masses extremely increase the selectiv ity factor, but the stability decreases in the long run. (C) 1998 Else vier Science B.V.