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 CO ₂ permeability (≈73Barrer) 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 0.5-2parts 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 2-4phr Pluronic contents an enhancement of CO ₂/CH ₄ (α≈33) and CO ₂/N ₂ (α≈97) selectivities was observed. According to thermal analysis, these results were attributed to the presence of ethylene oxide-propylene oxide units which increase CO ₂ 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.