ON THE GAS-PERMEABILITY OF HYDROXYL TERMINATED POLYBUTADIENE BASED POLYURETHANE MEMBRANES

A series of hydroxyl terminated polybutadiene (HTPB) based polyurethan es (PU) were synthesized by solution polymerization with different kin ds of polyols and diisocyanates, hard segment contents, NCO/OH value, polymerization methods and annealing time. The segregation between har d and soft segments was manifested by incompatibility between hard and soft segment, steric hindrance of urethane groups and the extent of i nterchain hydrogen bonding. Hydrogen bonding index (HBI) measured by F TIR was employed to show the extent of interchain hydrogen bonding, wh ich affects the segregation and hence gas permeability of the prepared membranes. Membranes with high HBI were seen to have low segregation and hence low gas permeability. Membranes with mixed diisocyanates of polar 4,4'-diphenylmethane diisocyanate (MDI) and nonpolar isophorone diisocyanate (IPDI), lower hard segment content and NCO/OH value, and one-stage polymerization methods exhibit higher gas permeability.