Heterogeneous reinforced (HR) polywinylidene fluoride(PVDF) hollow fiber membranes consisting of polyvinyl chloride (PVC) matrix membrane and PVDF coating layer were fabricated via concentric circles coating process.The polyvinyl chloride (PVC) matrix membrane with macroporous structure was prepared by melt-spinning method.While the coating layer was obtained by non-solvent induced phase separation method with PVDF as the polymer matrix

dimethylacetamide (DMAc) as the solvent

and polyvinylpyrrolidone (PVP) as the pore-forming agent.During the coating process

high concentration DMAc of polymer solutions could infiltrate into the surface pore of PVC hollow fiber membranes due to the effect of capillary force.Interface layer was formed between the coating layer and the matrix membrane of the HR PVDF hollow fiber membranes with compact structure.Therefore

pre-wetting solutions were used for the pretreatment of PVC matrix membranes before the coating process.The influences of pre-wetting solutions on structure and performance of HR membranes were investigated.The results showed that the interface layer of HR membranes without pre-wetting solutions was thick and dense.Because of the protection of pre-wetting solutions to surface pores of matrix membrane

the interface layer of HR membranes was thin and porous.The performance of HR membranes with pre-wetting solutions of ethanol and ethanol aqueous solutions were better than that of the DMAc aqueous solutions.The optimal permeability of HR membranes was obtained as the ethanol concentration of pre-wetting solutions reached to 60 wt%.The tensile strength of HR PVDF hollow fiber membrane was nearly 9 MPa.The results also showed that the interface adhesion between reinforcement and separation surface had a good combination in the range of 40% elongation.