热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

Preparation and Performance of Poly(vinylidene chloride-co-vinyl chloride) Porous Membranes via Thermally Induced Phase Separation

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物,邻苯二甲酸二甲酯(DMP)为稀释剂,采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜.通过聚合物-稀释剂二元体系相图、场发射扫描电镜(FESEM)、差示扫描量热仪(DSC)、X射线衍射(XRD)、原子力显微镜(AFM)、纯水通量、接触角、孔径及其分布、截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响.结果表明,P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主,随着聚合物含量增加,膜的横截面由类花瓣状结构向胞腔状结构转变,膜的孔连通性降低,结构变得较为致密,同时膜上表面孔隙率降低,粗糙度增大. L-L分相时间和聚合物含量的变化,导致膜结晶度先降低后增大.聚合物含量的增加使膜上表面接触角、断裂强度及蛋白截留率增加,但膜的平均孔径、孔隙率及纯水通量先增加后减小.当聚合物质量分数为30%时,所得膜通透性较优,断裂强度可达7.5MPa.

Poly(vinylidene chloride-co-vinyl chloride)[P(VDC-co-VC)]porous membrane,which had a homogeneous structure,was prepared by thermally induced phase separation(TIPS)method with dimethyl phthalate(DMP)as the diluent.The microstructures of P(VDC-co-VC)porous membranes were observed by field emission scanning electron microscopy(FESEM),differential scanning calorimetry(DSC),X-ray diffraction(XRD),atomic force microscopy(AFM).The effects of polymer content on the morphology and properties of P(VDC-co-VC)porous membranes were investigated by polymer-diluent binary system phase diagram,terms of porosity,pure water flux,contact angle and mechanical strength test etc.The results showed that the membrane formation process of P(VDC-co-VC)-DMP binary system was dominated by liquid-liquid(L-L)phase separation.With the increase of the polymer content,the cross-sectional structure of the membrane came from petal-like structure to cavity structure.In the structural transformation,the pores connectivity of the membrane cross-section were reduced and the structure became denser.At the same time,the porosity on the top surface of the membrane decreased and the roughness increased.The changes of L-L phase separation time and the polymer content caused the crystallinity of the membrane decreased and the partial crystallization peak disappeared or decreased.The membrane crystallinity increased as the polymer content reached to 40%,which indicated the greater correlativity of the phase separation time and the polymer content to the membrane crystallinity.In the flux testing stage,the pure water flux of membranes prepared with low polymer content appeared a large attenuation with the prolonging of testing time,which indicated poor compaction resistant ability for the membrane fabricated by low polymer content,while the increase of the polymer content could improve the membrane compaction resistant ability strongly.During the protein retention stage,the concentration polarization formed a filter cake layer that increased the protein rejection,while the permeate flux was tended to be stable.The increase of the polymer content brought about the increase of the contact angle of top surface,tensile strength and protein rejection,but the mean pore size,porosity and pure water flux increased first and then decreased.When the polymer content was 30%,the prepared membrane had excellent permeability and the tensile strength was 7.5 MPa.