PVDF-g-PAA共聚物的制备及其改性PVDF膜

为了改善聚偏氟乙烯（PVDF）膜的亲水性，本文通过自由基聚合法，以水/乙醇混合溶液为溶剂，合成了以PVDF为主链，聚丙烯酸（PAA）为侧链的PVDF-g-PAA两亲性共聚物。通过改变丙烯酸（AA）浓度合成了三种不同接枝率的PVDF-g-PAA共聚物，红外(FT-IR）及热重分析(TGA)结果显示接枝率以AA单体浓度10%为最高。以PVDF-g-PAA共聚物为膜材料，采用浸没沉淀法制备膜，通过扫描电子显微镜（SEM）、接触角测试和过滤实验考察膜的形貌及性能。结果表明，随着接枝率的升高，改性膜的平均孔径及孔隙率随之增大，接触角随之降低，表明其亲水性有很大的改善。在保持较好分离效果的基础上，改性膜的水通量及通量恢复率比原膜分别提高了3.78倍和0.76倍，表明其渗透性能及抗污染性能都有很大改善。

Preparation and Modification of PVDF-g-PAA Copolymer on PVDF Membrane

In this paper, an amphiphilic copolymer (PVDF-g-PAA) having poly(vinylidene fluoride)(PVDF) backbones and poly(acrylic acid)(PAA) side chains was synthesized via radical polymerization method in water/ethanol mixed solution to improve the hydrophilicity of PVDF membrane. Three PVDF-g-PAA copolymer samples of defferent grafting percentage (GP) were prepared by varying the concentration of AA. The results of Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA) indicate the GP at 10% AA concentration was the maximum among them. The copolymer was cast into membrane via immerse precipitation method. Scanning electron microscopy (SEM)、water contact angle measurement and filtration experiment were applied to evaluated the morphology and performance of membranes. It was found that mean pore size and porosity of modified membranes were increased with the increase of GP, but the contact angle of modified membranes decreased, indicating an improved hydrophilicity. Under high separation performance, the water flux and flux recovery ratio of modified membranes were enhanced by 3.78 times and 0.76 times, respectively, which means the permeate ability and fouling resistance of modified membrane have been great improved.