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Gas Permeability of Thermoplastic Polyurethane Elastomers

We have studied the influence of the chemical structures of thermoplastic polyurethane elastomers (TPUs) on their permeability to carbon dioxide and oxygen. The gas permeability of a TPU was dependent on the chemical structures not only of the soft segments but also of the hard segments. A TPU whose soft segment consists of poly(oxytetramethylene) exhibited a higher carbon dioxide permeability than does a TPU with ester bonds in the soft segment. The introduction of poly(dimethylsiloxane) chains into the TPU markedly enhanced the carbon dioxide permeability. In a series of TPUs containing poly(oxytetramethylene)glycol (PTMG), the gas permeability increased with the chain length of the soft segments. In the dissolution–diffusion process of gas permeation, the diffusion process predominated.