Study On Synthesis And Gas Separation Properties Of Hyperbranched Polyimide

As a material widely used in industry and life,polyimide has the advantages of high temperature resistance,excellent mechanical properties and solvent resistance.It has been widely used in gas membrane separation research.In this paper,two kinds of hyperbranched polyimide polymers were designed and synthesized,and gas separation composite membranes were prepared and characterized by XRD,TGA,FE-SEM and other methods.The effects of the type of polymer,preparation method and doping amount on the permeability and separation performance of nitrogen,carbon dioxide,methane and oxygen were studied,The gas separation composite membrane with high selectivity,high permeation rate and solvent resistance is prepared to promote the development of the gas separation composite membrane.Thepaperuses1,3,5-tris?4-aminophenyl?benzenetoreactwith4,4'-?Hexafluoroisopropylidene?diphthalic anhydride?6FDA?to synthesize a gel-state hyperbranched polyamic acid and load it on nylon-6,and then,drying into a hyperbranched polyamic acid?Paa?composite membrane;and a hyperbranched polyimide?PI?composite membrane was further prepared by chemical imidization.The gas separation performance of carbon dioxide,nitrogen and methane was studied.The permeability of polyamic acid Paa and polyimide PI composite membranes was very high,reaching more than 30,000 barrer,but the ideal separation coefficients of the three gases were small.The separation coefficients of N₂/CO₂,CH₄/CO₂ and CH₄/N₂ of the PI composite membrane were 1.2,1.89 and 1.57,respectively.The experimental results show that the hyperbranched polymer has strong affinity with nylon-6 and has excellent gas permeability,and is suitable as a support layer of the composite membrane.The inexpensive melamine was reacted with 3,3',4,4'-biphenyl dianhydride?BPDA?to synthesize hyperbranched polymers MAB1,MAB2,MAB3 under three different reaction conditions.MAB1,MAB2,MAB3 as a filling material and P84 blend to prepare a mixed matrix membrane for the separation of nitrogen and oxygen.MAB1 was synthesized by solid phase reaction in a tube furnace.When the doping amount was 30 wt%,the gas permeability to nitrogen was 147 barrer,and the selectivity of N₂/O₂ was 1.93.MAB2 was synthesized by NMP solvothermal reaction.When the amount of 7.5 wt%is increased,the permeability of nitrogen is increased to 541 barrer,and the selectivity of N₂/O₂ is 2.02.The solvothermal reaction of DMAc is used to synthesize MAB3.When the doping amount is 20 wt%,the nitrogen permeability is 466 barrer,the highest selectivity was 2.13.The experimental results show that the structure and preparation method of the filler material play an important role in improving the gas permeability and gas selectivity of the polymer.The development of a new filling material with a simple synthesis process and low cost has a practical significance for promoting the research of gas separation membranes.