Abstract: The permeability coefficient(P_g)of polyurethane(PU)with polybutylene adipate(PBA) or polypropylene glycol(PPG)as soft segment has been investigated.Both the types and length of the soft segment have great effect upon the gas permeability.PU with PPG segment shows higher gas permeability than that with PBA segment,Increasing the soft segment length brings about an increase in gas permeability and a decrease in the apparent activation energy. The linear relationship between P_g and the composition of the mixed soft segments indicates that the permeability coefficients of PU with PBA and PPG as soft segment are additive.

Key words: Polyurethane membrane, Gas permeability, Soft segment