Study On Surface Modification Of Poly (Vinylidene Fluoride)Membrane

Poly(vinylidene fluoride) (PVDF) is a kind of membrane material with excellent properties, such as the outstanding chemical and thermal resistance. However, the inherent hydrophobicity and low surface energy of PVDF membrane makes it be easily fouled when used in aqueous separation process, such as food, beverages and protein separation. In this paper, the method of surface grafting was used to immobilize hydrophilic monomers onto the membrane surface. The effect of different reaction conditions on the performance of PVDF membranes was investigated. Specific research contents and results are as follows:Firstly, acrylic monomers were grafted onto the PVDF membrane with the thermal grafting polymerization after alkaline treatment. FTIR spectra indicated that the grafted membrane has an obvious absorption peak appeared at 1720cm"1, which is associated with the-COOH stretching. The emergence of Ols characteristic peaks in the XPS spectra and the analysis of SEM demonstrated that the grafted monomer existed on the membrane surface. The results showed that the alkaline treatment system has a great impact on the membrane grafting ratio. And the membrane grafting ratio can be increased by changing the monomer concentration, initiation type and other conditions. After the grafting modification, the pure water flux decreased with the increase of the grafting ratio. The hydrophilicity has a significant improvement with the contact angle decreased from 130° to 36.5°.Secondly, the anti-fouling performance of the grafted membrane has been greatly enhanced after the esterfication reaction. The static protein adsorption decreased significantly of the modified membranes, when the grafting ratio was 16.9wt%, the amount of protein adsorption reduced to 4μg/cm2. Besides, the water flux after protein fouling almost returned to the values pre-contamination. The hydrophilicity of the PVDF membrane has a significant improvement with the contact angle dropped to 60.5°. And this can also be confirmed from the protein fouling experiment.Finally, the hydrophilic monomer PEGDMA and EGDMA were grafted onto the PVDF membrane, and the performance of the two grafted membranes was compared. Based on the result of the experiment, the modification effect of the grafted membrane prepared by PEGDMA is better than EGDMA.