湿法PVDF多孔膜的制备

Preparation of wet porous PVDF membrane

以DMF为溶剂、以PVA为添加剂,采用传统浸没沉淀法制备了改性PVDF多孔膜,并考察了DMF浓度、PVDF固含量、PVA含量和凝固浴温度等因素对多孔膜外部孔径及内部微球尺寸的影响.结果表明:随凝固浴中DMF浓度的增加,PVDF膜结构的泡孔尺寸变小,指形孔结构也相对变小;随PVDF固含量的增大,DMF从铸膜液中析出的量变少,膜内空间置换变缓,表面指形孔和内部微孔结构均变小;随成膜温度的升高,三相交换变剧烈,PVDF微滤膜的孔径变大.此外,随凝固浴中DMF和PVA浓度的增加,PVDF微球的晶体结构会变得光滑,尺寸增大;多孔膜的拉伸强度随PVDF固含量的升高和铸膜液中DMF浓度的降低而增大;PVA的加入改善了PVDF薄膜的亲水性,使其水接触角从108.3°降低至63°,亲水性有所提高.

Using DMF as solvent and PVA as modifying additives,PVDF porous membrane with well hydrophilic was prepared by conventional immersion precipitation method.The effects of DMF concentration,PVDF solids content,PVA content and coagulation temperatures on the internal structure of porous membranes were investigated.It was shown that the cell size and finger pore of PVDF membrane decreases with increasing the concentration of DMF in coagulation bath.In addition,with the addition of PVDF concentration,the double diffusion rate slows down,which results in the formation of smaller finger shaped hole.However,the pore size increases with the temperature of the coagulation bath because of the increased exchange rate.With the increase of the coagulation bath concentration of DMF and PVA,PVDF microspheres become smoother and bigger.Tensile strength of PVDF microfiltration membrane increases with escalating of PVDF solid concentrations and reducing of DMF concentration in casting solution.PVA was added to improve the hydrophilic property of PVDF films and the water contact angle reduced from 108.3°to 63°as expected.