Epoxidized HTPB-based Polyurethane Membranes for Pervaporation Separation

Polyurethane (PU) solutions were synthesized with hydroxyl-terminated polybutadiene (HTPB), 4,4′-dicyclohexylmethane diisocyanate (H12MDI) and 1,4-butanediol (1,4-BD). PU membranes were prepared by dry/wet method from PU solutions, while epoxidized membranes were prepared by dipping the dried PU membranes into a mixture of formic acid and hydrogen peroxide for the reaction with C=C double bonds of HTPB soft segments. The extent of epoxidized reaction, which forms epoxide or ether groups, on the PU membranes was quantified by the absorbance ratio of the epoxide group to the butadiene group (Aepoxide/AC=C ratio). Effect of epoxidized time on the polymer composition, morphology, and polarity of these HTPB-based PUs was investigated by FTIR-ATR, DMA and contact angle meter. Both permeabilities and permselectivity of a water/ethanol mixture, which is measured by pervaporation method, were improved through the epoxidation of PU membranes.