Preparation and properties of PVDF/PVA blend membranes

The membrane was prepared from PVDF/ PVA blend polymer by L-S phase inversion method.The compatibility of PVDF/PVA and the effects of PVDF/PS blend ratio,polymer concentration,additive,coagulation bath and after treatment on blend membranes performance were studied.The results showed that:(1) PVDF /PVA were incompatible blends,new interface microvoid structure was produced as a result of phase separation in PVDF/PVA;(2) With PVA content increased,the water flux of PVDF/PVA blend membrane increased due probably to the new interface microvoid structure,and decreased with PVA content increased again,which reached the maximum when PVDF/PVA was 8/2(wt/wt).The trends of rejection ratio and alcohol flux are contrary.PVA could improve the hydrophilicity of PVDF/PVA blend membranes,which could be illuminated by the decrease of contact angle;(3) The membrane thickness and rejection ratio increased whereas porosity and water flux decreased with polymer concentration increased;(4) The blend membranes performance was the best when PEG600 concentration ratio was 6%;(5) The composition of coagulation bath were much effective for porous structure and blend membranes performance;(6) The blend membranes performance could be improved due to the compact porous structure by heat treatment.Top-quality PVDF/PVA blend membrane could be obtained through selecting proper preparation condition,blending was an efficient method to improve the PVDF membrane performance.