Studies On Positively Charged Membrane From PDM/PAN Semi-ipn Blend System

The paper was aimed to prepare a novel positively charged membrane from RDM/PAN Semi-interpenetrating polymer network (Semi-IPN) blend system, which included the bulk polymerization of N, N-dimethylaminoethyl mecrylate (DM), the blend of its polymer (RDM) with polyacrylonitrile (PAN) which had good miscibility with RDM, the crosslinking and quaternizing of RDM, and the preparation of positively charged flat and tubular membrane from this Semi-IPN blend system.The polymerization of DM was studied firstly. RDM could be obtained through bulk polymerization and it was found that the effects of temperature, initiator, and inhibitor on the polymerization accorded with the general rules of free radical polymerization.RDM could form a uniform and stable solution in macroscope with PAN in N, N-dimethylacetamide (DMAc). And further investigation of viscosity and glass transition of the blend system proved that the RDM/PAN blend system had a good miscibility while PDM possessed a lower proportion in the blend.The crosslinker, DBBT, could crosslink and quaternize or encharge, in ether words, PDM simultaneously. Results of viscosity measurement showed the degree of crosslinking rised with the increase the temperature, time and dosage of the crosslinker.Membranes were prepared from single PAN, PDM/PAN blend without crosslinking and crosslinked PDM/PAN blend through phase inversion, respectively. The effects of polymer concentration of blend, blend ration, additive dosage and degree of crosslinking on the separating performance of membrane were carefully investigated. And its electric property was characterized using charged dyes. The crosslinked blend membrane had the best separating performances including good resistance against solvent andmicrobes, but it was a little brittle.Environmental scanning electron microscope and light microscope were employed to observe and study membrane microstructure, and pore-forming model of this kind of charged membrane was suggested.Positively charged tubular membrane was prepared using the one-step process in which tube-rolling and membrane-coating were completed at the same time. Its properties were valued on a specially designed device. We found its flux decreased while its rejection kept basically unchanged as the degree of crosslinking increased.Cathodal electrophoretic paint was ultrafiltrated respectively using tubular membrane made from PVDF, 1-hour and 4-hour crosslinked RDM/PAN blend. The 4-hour crosslinked tubular membrane had the best ultrafiltration performance.