Preparation And Research Of Solvent-Resistant Polyimide Nanofiltration Membrane

In this paper, both the pyromellitic dianhydride and 4,4'-diaminodiphenyl ether as monomers, N,N'-dimethyl acetamide as solvent, polyamic acid were prepared. Polyamic acid membranes were prepared through phase inversion method, and then imidization make changes through the polyamic acid membrane into polyimide membrane.The effects of the polyamic acid concentration of casting solution, non-solvent solidification temperature and composition influence the polyimide nanofiltration membrane structure and permeability properties of membrane, from the results, with the casting solution polyamic acid concentration increased, macroporous membrane structure gradually to changes in structure, while gradually reducing the membrane porosity, the permeability of polyimide membranes also reduce performance. Another solution with the solidification temperature, membrane structure refers to the ensuing changes variable length, while the structure within the cavernous holes also become larger in diameter. And with increasing temperature, the membrane permeation flux increased retention rate. This is because when the coagulation bath temperature, the faster molecular motion, non-solvent to the membrane in the proliferation of faster and faster membrane solvent exchange, accelerated the growth of nuclear dilute to form a larger hole.Further study on how the method of imidization influence on polyimide nano-filtration membrane structure and imidization degree. Imidization with different methods of membrane structure was not obvious, but the impact of membrane surface structure greatly different. Extent of imidization, thermal imidization can change the comparison is totally imidization and chemical imidization with the polyamic acid imidization reagents in the membrane of the soaking time, with the extension of soaking time, sub-continuously improve the level of amines in the 24h soaking agent in the film, the degree of imidization close 90% of the membrane after 48h immersion imidization degree of 98% close to the thermal imidization degree.Preparation of the final inspection of the polyimide membrane on the solvent-resistance performance of different solvents, the experimental use of five kinds of common organic solvents, after soaking the membrane from the morphology, swelling ratio, flux and tensile strength, the prepared polyimide membranes was not worth in esters, and excellent in alcohols and polar aprotic solvent tolerance performance.