Preparation And Properties Of Hyperbranched Polymer Cross-linked Membrane

Unlike the linear polymers, hyperbranched polymer (HBP) has a variety of functional groups, nano-voids, small rheological volumes. In this work, hyperbranched polymer crosslinked membrane was prepared by crosslinking the ended hydroxyl group and used to separate mixture solvent through the pervaporation membrane process for the first time.The hydroxyl values indicated that the perfect degree of hyperbranched polyglycerol(HPG) was lower than that of hyperbranched poly(amine-ester)(HPAE). The TG curves displayed that the heat-resistant property of HPG was better than that of HPAE.The HPG weight reduces at the beginning of 350℃ and HPAE weight reduced at the beginning of 150℃.The dense films were prepared by crosslinking the ended hydroxyl group of HPAE using Glutaraldehyde(GA). The surface structures of the crosslinked HPAE films were imaged using SEM, and their properties were characterized by hydrophilicity, solvent swelling and mechanics. It was found that the water static contact angle on the upper surface of the crosslinked HPAE films were smaller than 45°, the tensile strength was 12.3 Mpa, the swelling degree was higher than 63 percent in water. The crosslinked HPAE membranes were used as pervaporation membrane to separation the mixture of water and isopropanol. The flux was increased accompanied with the decrease of the separation factor when the water concentration in the feed solution was increased. The separation factor could reach 27.6 and the penetrate flux reach 2014.8g/m~2h when 100μm thickness membrane (hydroxyl/aldehyde group molar ratio= 2) was used to separated isopropanol mixture containing 10wt% water.The dense films were prepared by crosslinking the ended hydroxyl group of HPG using 3,3',4,4' - biphenyl tetracarboxylic dianhydride ( BPDA ) , 3,3',4,4' - benzophenone tetracarboxylic dianhydride (BTDA) , 4,4' - oxydiphthalic anhydride (ODPA) . Their properties were characterized by hydrophilicity, solvent swelling, thermal gravity and mechanics. The tensile strengths were greater than that HPAE cross-linked film by GA. Especially, The tensile strength HPG cross-linked film by ODPA wasthe greatest of the three films. The thermal gravity temperatures were higher than HPAE film. Withhydroxyl/anhydride group molar ratio 4:1, the water contact angles order of HPG film with different cross-linking sample is BTDA> BPDA> ODPA, the swellen degrees order is ODPA > BTDA > BPDA. It is found that the cross-linked film by ODPA is better hydrophilic.The composite membranes were prepared through coating ODPA cross-linked HPG casting fluid on PE, PVDF/PET, CA/PET and PET membrane. The pervaporation properties of the composite membrane were characterized via separation the mixture of water and isopropanol. The flux was increased accompanied with the decrease of the separation factor when the water concentration in the feed solution was increased.In the separation of isopropanol mixture containing 1 Owt% water, the penetrate flux order of different substrate composite membrane (hydroxyl/anhydride group molar ratio at 4:1) was CA/PET> PVDF/PET> PE> PET, the separation factor order was PET> PVDF/PET> CA/PET> PE. The separation factor of PET composite membrane reached 202.8 and the penetrate flux reached 239.8g/m2h. The flux was increased accompanied with the decrease of the separation factor when hydroxyl/anhydride group molar ratio was increased. The separation factor reached 164 and the penetrate flux reached 785.4g/m2h when PET composite membrane (hydroxyl/anhydride group molar ratio at 4:1) was used to separate ethyl acetate mixture containing 10wt% ethanol.