6333 pebax 2533 pebax 3533 pebax 1205 pebax 3000 pebax 1657 or pebax 1074 pebax 1657 exhibits a methane permeability of 5 12 barrer h rabiee et al j membrane sci vol 476 pp 286 302 2015 in contrast pdms exhibits a methane permeability of 800 barrer stern et al j appl polym sci vol 38 2131 1989 the pebax polymers have the following general chemical structure where pa is an aliphatic polyamide u201c hard u201d block nylon 6 pa6 or nylon 12 pa12 and pe denotes a polyether u201c soft u201d block either poly ethylene oxide peo or poly tetramethylene oxide ptmeo commercial available polyactive multiblock copolymers have the following general chemical structure while the gas separation membrane s of the first gas gas separation membrane stage 3 may have any configuration known in the field of gas separation typically they are formed as a flat film or as a plurality of hollow fibers in one embodiment the separation layer is supported by a support layer where the separation layer performs the desired separation while the support layer provides mechanical strength in the context of hollow fibers the separation layer is configured as a sheath surrounding a core made of the support layer regardless of the configuration of the membrane the support layer may be any porous substrate known in the field of gas separation membranes and includes but is not limited to polyimides polysulfones and polyether ether ketones typical hollow fiber membrane supports are peek porous substrate fibers commercially available from air liquide advanced separations a unit of air liquide advanced technologies us typically.