Study On Regulation Of PSF Microporous Membrane Structure And Performance Via RTIPS Method

The ternary systems of Polysulfone (PSF)-N,N-Dimethyl Acetamide(DMAc)-polyethylene Glycol(PEG200, PEG400and PEG600) with low critical solution temperature (LCST) were explored. The LCST and preparation methods of reverse thermally induced phase separation (RTIPS) in PSF-PEG-DMAc systems were confirmed by Hansen solubility parameter theory and the experimental of transmittance curves. The effects of RTIPS preparation method on regulation of PSF microporous membranes structure and performances were discussed, which were characterized by flux, retention rate, mechanical properties, average pore diameter, SEM and so on. Preferable results are obtained as follows:Firstly, the LCST systems of PSF-PEG-DMAC were only suitable for non-solvent of PEG400and PEG600. Furthermore, when the mass concentration of PSF was between16%and20%or the casting solution had additives, the two LCST systems were still existence. LCST became lower as the mass ratio of PEG/DMAC increasedSecondly, the effects of casting solution composition, coagulation bath temperatures and membrane preparation method on structure and performance regulation of PSF flat membrane were investigated, which were based on the ternary LCST systems of18%PSF, PEG400/DMAC=1.1. With increasing of coagulation bath temperatures or PSF mass concentration, the retention and mechanical properties were improved, while the flux and the surface pore size were decreased and the cross-section structure tended to sponge sharp. The membrane prepared via RTIPS had higher flux, lower retention, excellent mechanical properties and easier sponge sharp of cross-section when compared to NIPS. When the LCST system had1%TEP and coagulation bath temperatures was60℃, the best comprehensive properties of PSF flat membrane prepared via RTIPS-NIPS method were as follows:The flux was520L·m-2·h-1·bar-1, the average pore size was0.048μm, the break strength was7.06MPa, the surface pore size was well-distributed and the cross-section was sponge structure.Lastly, PSF hollow fiber membrane was prepared via RTIPS-NIPS method on the basis of casting solution of18%PSF,1%TEP, PEG400/DMAC=1.1. The effects of dry-spinning distance, coagulation bath temperatures, additive of1%TEP and core liquid composition on structure and performance regulation of PSF hollow fiber membrane were discussed. With the dry-spinning distance decreasing or coagulation bath temperatures increasing, the permeability and mechanical property were be improved. The inner cortex was disappearing and the flux was improved as the DMAC mass proportion of the core liquid increasing, which also could led to poor mechanical property and retention rate. The best properties of PSF hollow fiber membrane were as follows:the flux was103L·m-2·h-1·bar-1, the retention rate was43.4%, the break strength was6.02MPa, the elongation at break was43.7%, and good hydrophilic properties. The distribution of membrane pore size was concentrated in the range of5nm-25nm, which was a typical hollow fiber Ultrafiltration membrane.