关键词: 共混膜, 微观结构, 水通量, 亲水性, 抗污染性能

Abstract: Polyvinyl chloride (PVC) is one of the main membrane materials in modern times. It has excellent acid and alkali resistance, microbial resistance, high mechanical strength, low price and other advantages, and is widely used in ultrafiltration, nanofiltration and other fields. However, the film forming performance of PVC is not very ideal, the water flux is low, and the toughness is insufficient, so it is easy to shrink and wrinkle spontaneously when gel is used. Therefore, the PVC film needs to be modified by blending to improve its performance. Polyvinylidene chloride (PVDC) has good film forming property, good mechanical properties, thermal stability and chemical resistance. Therefore, blending PVC and PVDC can make the film have both advantages. In addition, due to the poor hydrophilicity of PVC and PVDC, polyethylene glycol (PEG) can be used as an additive to modify the blend membrane, which can improve its hydrophilicity, pollution resistance and pure water flux.
In order to investigate the preparation and properties of polyvinyl chloride(PVC)/poly(vinylidene chloride) (PVDC) blend membranes, N, N-Dimethylacetamide (DMAC) was used as solvent to prepare PVC/PVDC blend membranes by phase inversion method. The compatibility of PVC/PVDC blend system, the surface morphology and cross-sectional morphology of blend membranes, as well as the effects of blend ratio and polyethylene glycol (PEG) mass fraction on pure water flux, rejection, dynamic contact angle and flux recovery were studied. At present, a lot of studies on the blending modification of PVC membranes have been done at home and abroad, but the study on the modification of PVC membranes with PVDC has not been reported yet. The results show that when the blending ratio is 4/6, the overall performance of the blend membrane is the best, the pure water flux is 212.9 L/(m²·h), and the rejection rate of bovine serum albumin (BSA) is 88.5% under the pressure of 0.1 MPa. The optimum mass fraction of PEG is 6%, and at this time, the pure water flux is 336.6 L/(m²·h), the interception rate is 81.6%, the instantaneous contact angle decreases from 81.1° to 74.5°, and the recovery flux rate increases from 52.7% to 85.7%. The results show that PEG can effectively improve the hydrophilicity and anti-protein pollution ability of the blend membrane.
In this paper, PVC/PVDC blend membranes are prepared by phase inversion method. The compatibility of PVC/PVDC blend systems is analyzed and discussed by measuring the shear viscosity of solutions with different blend ratios. At the same time, the surface and section microstructures of PVC/PVDC blend membranes are observed by field emission scanning electron microscopy (SEM), and the contact angle, pure water flux and flux recovery rate and the interception rate of bovine serum albumin (BSA) are tested to determine the optimal blend ratio. On this basis, the influence of PEG mass fraction on the performance of the blend membrane is studied to determine the optimal PEG content, which provides some directions for the material selection and modification of PVC blend membranes, and endows them with a broader market prospect in water treatment and sewage treatment.

Key words: blend membrane, microstructure, water flux, hydrophilicity, anti pollution performance