Afsaneh Khosravi - Chemical Engineering Department, Isfahan University of Technology, Isfahan ۸۴۱۵۴, Iran
Morteza Sadeghi - Chemical Engineering Department, Isfahan University of Technology, Isfahan ۸۴۱۵۴, Iran
mehdi Tala kesh - Chemical Engineering Department, Isfahan University of Technology, Isfahan ۸۴۱۵۴, Iran
Brian Kraftschik - School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA

In this research the effects of changing the polyol, disocyanate, and chain extender used in synthesized polyurethane membranes on gas permeability were investigated. The membranes used in this study were prepared using PTMG, PPG or PCL as the polyol, IPDI, HDI or TDI as the diisocyanate and BDO or BDA as the chain extender. They were synthesized in a 1:3:2 molar ratio of polyol:diisocyanate:diol.DSC and WAXD studies confirmed that changing the polyol type from PPG to PTMG and then PCL increases phase interaction in PCL based polyurethanes in comparison with the other samples. Furthermore, changing the isocyanate group from aromatic to aliphatic and from cyclic aliphatic to linear aliphatic lead to more phase interaction in TDI based polyurethane relative to the other samples. Additionally, modifying the chain extender from a diol to a diamine causes an increase in phase separation.The measured permeability results indicate that larger, more condensable gases are more permeable than light ones since the selectivity of the rubbery polyurethanes is dominated by solubility. On the other hand, by enhancement of the microphase separation of hard and soft segments, the rubbery behavior and permeability of condensable gases increases along with their selectivity. All in all, polymers based on the PPG polyol showed maximum permeability because of their high phase separation, polymers based on the TDI diisocyanate showed minimum permeability due to the greater amount of hard and soft segment connections, and both the permeability and the selectivity of polymers based on a BDA chain extender are more than those based on BDO due to the larger number of hard segments – in other words, more rubbery properties.

polyurethane, membrane, gas separation, chain extender, polyol, diisocyanate