Characterization and gas permeability of polyurethane and polyvinyl acetate blend membranes with polyethylene oxide–polypropylene oxide block copolymer

Blend membranes of polyurethane (PU) and polyvinyl acetate (PVAc) were prepared in the presence of various polyethylene oxide–polypropylene oxide–polyethylene oxide triblock copolymer (Pluronic) contents by solution casting technique with N,N-dimethylformamide as solvent. The blends with 5% (wt) PVAc showed higher CO2 permeability (≈73 Barrer) compared to the PU membrane. The domain size of the dispersed PVAc phase of PU/PVAc blend membranes was controlled by adding the Pluronic. When the Pluronic was added at 0.5–2 parts per hundred of PU/PVAc blend (phr) in PU/PVAc membranes in the range of the PVAc content of 5–15% (wt), the domain size of the dispersed phase was reduced markedly and its permeability was consequently increased. In the blend membranes with 2–4 phr Pluronic contents an enhancement of CO2/CH4 (α ≈ 33) and CO2/N2 (α ≈ 97) selectivities was observed. According to thermal analysis, these results were attributed to the presence of ethylene oxide–propylene oxide units which increase CO2 permeability and to a decrease of crystallinity in PU/PVAc blends. The experimental permeabilities of the blends were compared with the calculated permeabilities based on modified additive logarithmic model.