Research Of Surface Chemical Modification Of Pvdf Hollow Fiber Porous Membrane

Poly(vinylidene fluoride) is a kind of membrane material with excellent characteristics, in order to improve its surface hydrophilicity, so as to increase its antipollution ability, surface modification of PVDF hollow fiber porous membrane has been studied, on the bases of reviewing all kinds of modification methods, the modification method of chemical grafting onto hollow fiber membrane surface was determined. The paper includes three main aspects of works as follows:At first, the study of treatment with strong alkali and strong oxidant to PVDF hollow fiber membrane surface has been studied through changing reaction parameter, such as temperature, concentration and reaction time, mechanics performances of PVDF fiber before and after this treatment has been mensurated , its surface hydrophilicity was token by mensurating the first bubble pressure value, the optimal reaction conditions has been determined as follows: [KOH]=30wt%, [KMnO4]=3wt%, T=60, t=30min. After this reaction, active molecule were introduced onto membrane surface.Secondly, graft copolymerization reaction of PVDF membrane treated hereinbefore in the aqueous medium has been investigated. Respectively choose 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and bromide ammonium nitrate (CAN) as grafting monomer and initiator, and the extent of grafting was determined by measuring hollow fiber's weight, the optimal reaction parameters can be seen as follows: [Mohr's]=4.2 x 10~3mol/L, on such condition, grafting degree was 6.8%, and bubble pressure was 0.42MPa, grafted copolymer was verified by various techniques, including Fourier Transform infrared Adsorption Spectrum (FTIR), Scanning Electron Microscopy (SEM), Electron Spectroscopy of Chemical Analysis(ESCA).Lastly, the comparison of those PVDF hollow fibers membrane before and after modification has been studied by separately applied them to practically oil water (with confected concentration of 60mg/L) separation test, the decrease of water flux was measured, according to the results, grafted hollow fiber membrane showed better antipollution capability, it indicated that this method is practicable and effective.