EPDM as a selective membrane material in pervaporation

Various types of ethylene–propylene-diene terpolymers (EPDM) and crosslinking procedures have been investigated with pervaporation, vapor sorption, liquid sorption and gas permeation experiments. The EPDM parameters that have been changed are ethylene content, molecular weight, choice of third monomer, type of branching and various crosslinking procedures. The permeability coefficients were determined from pervaporation experiments and were about 40,000 Barrer for toluene and 700 Barrer for water. However, from vapor sorption measurements, a value of 22,000 Barrer for toluene was obtained which is somewhat lower. It should be realized that these data can only be compared qualitatively; the permeabilities obtained from sorption isotherms are derived data while in case of the pervaporation experiments it is experimentally measured. There is an indication that toluene behaves independently from water but the presence of toluene does influence the water flux during pervaporation. Gas permeation experiments resulted in permeabilities for CO2, O2 and N2 of 120, 24 and 11 Barrer, respectively. No clear differences were found for both EPDM-variation and different crosslinking procedures.