Research On Preparation And CO₂/N₂ Permeability Of PEBA/EPH Gel Membranes Via Solvent Evaporation Method

The adverse atmospheric phenomena caused by global warming have received worldwide attention. Carbon dioxide is widely accepted as the main green-house gas. CO2 separation has become an important constraint factor of sustainable development of economy and society. Membrane separation is an attractive technology because of energy saving, environmental protection. In recent years, people have done a lot of research on gel membrane, which is composed of polymer molecules with liquid functional gel medium to form a self-supporting structure by crystallization or hydrogen bond and other effects. Gel membrane possesses outstanding gas permeability and selectivity due to the liquid functional gel medium has a high CO2 adsorption and permeability. The key to achieve high permeability and selectivity is the choices of gel medium. Ethylene glycol monophenyl ether shows a strong ability to dissolve CO2 as the ideal gel medium.In this paper, ethylene glycol monophenyl ether(EPH) and polyether block amide(PEBA 1657) were selected as the gel medium and polymer to prepare three kinds of PEBA 1657/EPH gel membranes by solvent evaporation method. The effect of gas permeability with the change of physical and chemical structure was studied. The following conclusions are obtained:1. PEBA 1657/EPH gel membranes were prepared to research the impact of different EPH content and solvent evaporation rate on their thermal performances, mechanical properties and gas permeations. The results showed that both mechanical properties and the crystallinities decreased with the increase of EPH, but CO2 permeations were enhanced. When the content of EPH was up to 60 wt%, the permeability and separation factor of the PEBA 1657/EPH gel membrane were 320.8 barrer and 77.83, respectively. When solvent evaporation rate was increased, the gas permeability coefficient rose slightly, but the ideal selectivity reduced.2. EPH was modified with IPDI to increase its stability. PEBA 1657/IPDI-EPH gel membranes were prepared. The impact of different IPDI-EPH content and solvent evaporation rate on their thermal performances, mechanical properties and gas permeations were researched. The results showed that both mechanical properties and the crystallinities decreased with the increase of IPDI-EPH, but CO2 permeations were enhanced. When the content of IPDI-EPH was up to 60 wt%, the permeability and separation factor of the PEBA 1657/IPDI-EPH gel membrane were up to 204.9 barrer and 81.32, respectively. Meanwhile the stability of modified gel membrane was improved significantly. Also, when solvent evaporation rate was increased, the gas permeability coefficient rose slightly, but the selectivity decreased obviously.3. Add a surface layer through interfacial crosslinking reaction to achieve high permeability and stability. PEBA 1657/EPH interface crosslinked composite membranes were prepared. The impact of crosslinking time on their thermal performances, mechanical properties and gas permeations were researched. The results showed that both mechanical properties and the crystallinities enhanced with the increase of crosslinking time, but CO2 permeability coefficient were decreased and CO2/N2 selectivity were increased at the same time. When the crosslinking time were 60 min, the permeability and separation factor of PEBA 1657/EPH-60 interface crosslinked composite membrane were up to 163.3 barrer and 86.39, respectively.