Properties and pervaporation performances of crosslinked HTPB-based polyurethane membranes

Hydroxyl-terminated polybutadiene (HTPB), 4,4′-dicyclohexyl methane diisocyanate (H12MDI) and 1,4-butane diol are used to synthesize polyurethane (PU) solutions by a two-stage process. PUS with different equivalent ratios of NCO/OH from 1.0 to 1.5 are prepared. Thermal degradation temperature, tensile strength and contact angle of membranes are all increased with the increase of NCO/OH ratio. While the elongation of membranes is also increased with the increase of NCO/OH ratio, they are then decreased disruptly when NCO/OH ratio equals to 1.5. These PU membranes are used for the separation of ethanol/water, isopropanol/water solution by pervaporation test. Membranes with NCO/OH = 1.3 ratio possess the largest (36,713 g/(m2 h)) pervaporation separation index (PSI), while the ethanol concentration in the feed on the separation factor has different effect than that of IPA/water solution.