Preparation Of Polyurethaneurea Based Organic-inorganic Blend Membranes And Their Gas Separation Performances

The organic-inorganic hybrid membrane, combining the flexibility of polymer membrane and the selective advantage of inorganic membrane, has become the research hotspot of gas separation membrane materials. At present, a major difficulty faced to organic-inorganic hybrid membranes is the incompatibility between the inorganic additives and polymer, which leads to the formation of non-selective cavity and thus the restriction of separation performance of membrane in further increase. And the surface modification of inorganic additives is complicated and tedious, which also inevitably causes the pore blockage of the inorganic additives. Therefore, more effective and easy way should be directly blending inorganic additivies into amphiphilic polymers. Polyurethane constitutes the polar hard segments and the non-polar soft segments and their adhesive force to inorganic additives can be easily regulated according to the chemical structure and the composition of soft and hard segments.In this paper, hybrid membranes of polyurethane/4A zeolite, polyurethane/4Azeolite/ span-60 and polyurethane/ZIF-8 were prepared by a two-step polymerization process, which were used as membrane materials to investigate the adsorption property and the permeability of CO₂, H₂, O₂ and N₂. The main research contents and conclusions can be listed below:(1) The zeolite 4A particles were well dispersed in the PU matrix and the incorporation of the 4A significantly improved permeability of O₂ and ideal selectivity of O₂/N₂ and the thermal stability of the membranes with some compromise of mechanical properties. With the adding of zeolite 4A deferred, the selectivity of the various gas systems increased initially and then decreased, and the permeability increased initially then leveled off. Along with the increase of hard segment content, the gas permeability was all decreased while the selectivity of CO₂/N₂,O₂/N₂,H₂/N₂ increased and then decreased. The HTPB-PU/4A membranes containing 24.97 wt% hard segment showed the highest selectivity. As the increase of zeolite 4A, O₂ permeability continuously increased while the selectivity of O₂/N₂ ascended at first and descended afterwards. The HTPB-PU/4A membranes containing 10 wt% zeolite 4A showed the highest O₂/N₂ selectivity of 7.11.(2) The incorporation of the span-60 enhanced the thermal stability of the membranes apparently and span-60 were compatible with the PU segments, while the mechanical properties fell. With the accession of span-60, CO₂ adsorption performance of hybrid membrane is greatly improved. The span-60, which was added into HTPB-PU/4A /span-60 membranes, can significantly improve permeability of CO₂ and selectivity of CO₂/N₂. And the zeolite 4A, which was added into HTPB-PU/4A/span-60 membranes, can significantly improve permeability of O₂ and selectivity of O₂/N₂. The HTPB-PU/4A /span-60 membranes containing 3 wt% zeolite 4A and 1 wt% span-60 showed the highest CO₂/N₂ selectivity of 43.9, and the membranes containing 3 wt% zeolite 4A and 10 wt% span-60 showed the highest O₂/N₂ selectivity of 11.4.(3) The incorporation of the ZIF-8 particle enhanced the thermal stability of the membranes apparently and ZIF-8 particle were compatible with the PU segments, while the mechanical properties fell. The ZIF-8 particle has good adsorption of CO₂ and H₂. As the increase of ZIF-8, H₂ permeability continuously increased while permeability of O₂, N₂, CO₂ descended at first and ascended afterwards. The membrane shows high selectivity of CO₂/N₂ . The ZIF-8 particle, which was added into HTPB-PU/ZIF-8 membranes, can significantly improve permeability of H₂ and selectivity of H₂/N₂. As the increase of ZIF-8 particle content, the selectivity of H₂/N₂ ascended at first and descended afterwards. The HTPB-PU/ZIF-8 membranes containing 5 wt% ZIF-8 showed the highest H₂/CO₂ selectivity of 5.03.