PVDF/EVOH共混膜制备及其抗污染特性的分析

Preparation of PVDF/EVOH blend membranes and analysis of its antifouling ability

用相转化法对聚偏氟乙烯(PVDF)超滤膜进行了乙烯-乙烯醇共聚物(EVOH)共混改性,系统考察PVDF/EVOH共混比和凝胶浴温度对共混膜性能的影响.并使用原子力显微镜(AFM)胶体探针定量测定了共混改性前后,亲/疏水性污染物与膜之间作用力的变化特点,结合宏观过滤实验解析添加EVOH对PVDF抗污染性能的影响.结果表明:PVDF/EVOH相容性最佳的共混比为9∶1.与纯PVDF膜相比,PVDF/EVOH共混膜的亲水性明显提高.共混膜的亲水性及拉伸强度随着凝胶浴温度的增大而增大,但是纯水通量随着凝胶浴温度的增大而减小.主要是因为高凝胶浴条件下膜表面有致密的皮层形成。膜-污染物间作用力及污染试验表明,添加EVOH后有效降低了膜-污染物间的相互作用力及相应的膜污染速率,表明了EVOH的引入能有效改善了膜的抗污染性.

Polyvinylidene fluoride （PVDF）/ethylene vinyl alcohol copolymer （EVOH） blend membranes were prepared by phase inversion. The influence of PVDF/EVOH blend ratio and coagulation bath temperature on the properties of the blend membrane were investigated. Typical foulant probes were used to measure the change of foulant-membrane interaction force before and after the blend modification of PVDF membranes and analyze the antifouling characteristics of the modified membrane. The results show that the optimum blending weight ratio of PVDF/EVOH compatibility was 9 ： 1. The PVDF/EVOH membrane presented more hydrophilic than the pure PVDF membrane. The hydrophilicity and mechanical strength of blend membrane obtained increased with the coagulation bath temperature during the preparation, whereas its pure water flux decreased. The main reason is that PVDF/EVOH blend membrane with a dense layer in the surface formed. It is also found that the interaction forces between PVDF/EVOH and foulant were much weaker than those between the pure PVDF membrane and foulant. It suggests that the antifouling ability of PVDF membrane was effectively improved by blending EVOH.