Correlations between gas permeation and free-volume hole properties of polyurethane membranes |
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Authors: | Zhi Fen Wang Yu Run Yang |
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Institution: | a Department of Physics, Wuhan University, Wuhan 430072, China b Institute of Material Science and Engineering, East China University of Science and Technology, Shanghai 200237, China |
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Abstract: | A series of polyurethane films based on hard segments consisting of toluene diisocyanate and 1,4-butanediol and different soft segments consisting of hydroxyl terminated polybutadiene, hydroxyl terminated polybutadiene/styrene and hydroxyl terminated polybutadiene/acrylonitrile were synthesized by solution polymerization separately. Positron annihilation lifetimes were measured at room temperature for all samples studied. We found that both the free volume size and fractional free-volume decreased with the increase of hard segment content. On the other hand, direct relationship between the gas permeability and the free-volume has been established based on the free-volume parameters and gas diffusivity measured. Experimental results revealed that the free-volume plays an important role in determining the gas permeability. |
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Keywords: | Positron annihilation Free-volume Gas permeability |
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