Plasticization resistant crosslinked polyurethane gas separation membranes

Abstract

Polyurethanes (PUs) with good film formation ability and high gas separation properties are promising materials for gas separation membranes. However, low mechanical properties and high CO₂ plasticization limit the industrial application of these membranes. Here, we synthesized a crosslinkable PU structure using a 1 : 3 : 2 molar ratio of Pluronic L61, isophorone diisocyanate (IPDI) and 3,5-diaminobenzoic acid (DABA). In order to improve both mechanical properties and plasticization resistance, a series of crosslinking agents with different chain lengths and functionalities were used to crosslink the PU via an esterification-based reaction. Pure (H₂, CO₂, N₂, CH₄, and C₂H₆) and mixed (CO₂/N₂ and CO₂/CH₄) gas permeability experiments were performed on the crosslinked PU (XPU) membranes. The XPU membranes showed enhanced mechanical properties and chemical stability and improved plasticization resistance to an extent about three times higher than the non-crosslinked PU and commercial membranes (PEBAX® 2533). Mechanical tests indicated an improvement of over 600% in Young's modulus and 200% in hardness for XPUs compared to the pristine PU. The resulting crosslinked membranes with high CO₂ separation performance (CO₂/N₂ ∼ 30) and superior thermal and mechanical properties are attractive candidates for industrial separation processes.