The Study Of PVDF Blend Membrane Via Nonsolvent Thermally Induced Phase Separation

Poly(vinylidene Fluoride)(PVDF) was the widely used polymer membrane materials,is widely applied in various aspects,such as water supply engineering,industrial waste water, pharmaceutical industry, food industry, the application of the energy industry.Otherwise,the hydrophobic and easily polluted limit the application of PVDF membranes in the field of separation. Nowaday,PVDF membrane are usually produced via the phase conversion,mainly includes: nonsolvent induced phase separation(NIPS), thermal induced phase separation(TIPS), nonsolvent thermally induced phase separation(NTIPS).In this paper, on the basis of the preparation methods of PVDF membrane, the performance, strong hydrophilicity, asymmetric structureof PVDF blend membrane was prepared by NTIPS.The rheology of caprolactam(CPL) solutions blends with poly(vinylidene fluoride)(PVDF) was studied by using Rheometer.The influence of different percentage PVDF content,different temperature on the PVDF/CPL casting solution system of the viscosit,the non-newtonian index,the viscous flow activation energy,modulus of solution were inspected.The results show that PVDF/CPL casting solution system shows the characteristic of typical non-Newtonian fluid.The casting membrane system with high percentage PVDF content had high sensitivity to the temperature. The membrane with high percentage PVDF could be prepared over a wide range of casting speed at high temperature.The casting membrane system with low percentage PVDF content had low sensitivity to the temperature and the casting speed had a great effect on the preparation of the membrane. So the preparation of the membrane with low percentage PVDF needed precise control of the casting speed. It laid a theoretical foundation for the preparation of PVDF blend membrane.In this paper, PVDF and hydrophilic polymer(PMMA,PEO,PVA) blend with a soild water-soluble Caprolactam(CPL) was prepared by NTIPS.The influence of PVDF blend membrane was tested,such as the concentration of membrane material, blending ratio, composition of coagulation bath temperature. The mixing compatibility between hydrophilic polymer and PVDF were determined by differential scanning calorimeter(DSC).Scanning electron microscopy was used to observe structure of different PVDF blend membrane, Contact Angle tester was used to contact blend membrane’s hydrophilic.The results show that the PEO and PVA of hydrophilic modification of PVDF blend membrane effect is good, PMMA hydrophilic modification and the effect is not obvious,while the concentration of membrane materials increase, membrane pore diameter and porosity decreases, water flux decreased, the BSA retention increased.While PMMA blend ratio increased, PVDF crystal was affectted, leading to different layer structure.While PEO blend ratio increased, compatibility and the structure of the membrane is not good, because of the large molecular weight of PEO.The increase of the content of PVA strengthen PVDF membrane’s hydrophilic.With the increase of coagulation bath temperature, PVDF blend membrane increase macroporous structure.Finally,the PVDF/PMMA, PVDF/PEO,PVDF/PVA blend membrane’s resistance distribution were respectively analysised and further investigate the cleaning and restoring effect.The results showed that the PVDF/PEO and PVDF/PVA blend modification of membrane pollution resistance increase, cleaning effect is excellent.