凝固浴强度对原位聚合改性聚偏氟乙烯膜结构与性能的影响

Effect of coagulation bath strength on structure and properties of poly(vinylidene fluoride)membranes prepared by in situ polymerization method

采用原位聚合的方法得到聚偏氟乙烯(PVDF)与聚甲基丙烯酸羟乙酯(PHEMA)的均相共混溶液,以不同配比的水和溶剂磷酸三乙酯(TEP)的混合溶液作为凝固浴,通过非溶剂复合热诱导相分离方法,制备了系列具有互穿网络结构孔的亲水性PVDF微孔膜.X射线光电子能谱(XPS)分析表明,随着凝固浴中水含量的增加,PHEMA在PVDF微孔膜表面富集度增加.原子力显微镜(AFM)和扫描电镜(SEM)发现,随着凝固浴中水含量的增加,PVDF微孔膜上表面由开孔结构逐渐发展为致密结构,且粗糙度随之减小.通过动态接触角测试发现,随着凝固浴中水含量的增加,改性PVDF微孔膜初始接触角由139.7°降低到64.7°,水滴在膜表面的浸润时间由313s减小到16s.水通量测试表明,随着凝固浴中水含量的增加,PVDF微孔膜的纯水通量由2 300L/(m2.h)减小到400L/(m2.h),但由于具有良好的可润湿性,改性干膜仍然保持与湿膜相当的水通量.

A homogeneous solution of poly （vinylidene fluoride）（PVDF） and poly （2-hydroxyethyl methacrylate） （PHEMA） was prepared via in situ polymerization of 2-hydroxyethyl methacrylate （HEMA） monomers in a pre-dissolved PVDF solution. Subsequently, hydrophilic PVDF membranes with inter--connected pores were prepared by a non-solvent assisted thermally induced phase separation method using mixtures of water and triethyl phosphate （TEP） as the coagulant. X-ray photoelectron spectroscopy （XPS） results showed that the amount of PHEMA enriched on the membrane surface increased with the increasing of water content in the coagulant. The membrane morphologies were investigated by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. It was found that top surface evolved from open-pore to dense structure with the increasing of water content in coagulation bath, resulting in smaller surface roughness. With the increasing of water content in the coagulant bath, the hydrophilcity of formed membranes was greatly improved. Initial contact angle of the membranes dropped from 139. 7° to 64. 7 °while wetting time was reduced from 313 s to 16 s. The pure water flux of modified membranes was in the range of 2 300～400 L/（m2 · h）. Because of excellent wettability from the modification, thus formed dry PVDF membranes exhibited almost similar water flux to wet membranes.