Preparation And Performance Study Of PVDF/UHMWPE Flat Membrane With Microstructured Surface

Hydrophobic membranes inevitably caused membrane wetting and membrane fouling in use,affecting the use efficiency of the membrane.Many studies have been proposed to improve the anti-wetting and anti-pollution properties by increasing the hydrophobicity of the membrane surface.In this paper,a new method for preparing highly hydrophobic separation membranes was proposed.Polyvinylidene fluoride(PVDF)/ultra high molecular weight polyethylene(UHMWPE)flat membrane with high hydrophobicity was prepared by combining microimprinting and thermal induced phase separation(TIPS),and array microstructure was constructed successfully on the surface of the membrane.The effects of UHMWPE content and coagulation bath temperature on the structure and properties of PVDF/UHMWPE flat membranes were investigated.The surface morphology were characterized by scanning electron microscopy(FESEM)and atomic force microscopy(AFM);the crystallization behavior of the membrane was analyzed by differential scanning calorimetry(DSC);The hydrophobic properties,permeability,wettability resistance and mechanical properties of the membrane were measured by measuring the static water contact angle,pore size distribution,gas flux,LEP and mechanical strength of the membrane;The wettability and anti-protein contamination properties of the microporous membrane were analyzed using membrane wetting test and protein adsorption test,Characterizing the anti-pollution performance of the flat membrane in the application process。The results showd that the microarray structure on the surface of PVDF/UHMWPE blend membrane effectively increased the contact angle of the membrane surface.The successful construction of the microarray structure increased the surface roughness of the membrane,thus improving the hydrophobicity of the membrane.The microstructure replication accuracy of the membrane surface was related to the UHMWPE content and the coagulation bath temperature.UHMWPE content directly affectd the system viscosity of the casting solution Too large or too small viscosity of the casting liquid system was not conducive to the replication accuracy of the microstructure,and the use of a lower coagulation bath temperature facilitated the replication accuracy of the microstructure.When the content of UHMWPE was 4-6wt%,the viscosity of the casting liquid system was suitable for micro-imprinting,and the microstructure of the membrane surface has high replication accuracy and good surface hydrophobicity.Increasing the content of UHMWPE was beneficial to enhance the mechanical properties of the flat membrane,However,it would reduce the hydrophobic properties,permeability and wettability of the membrane.When the coagulation bath temperature was 20℃,the surface of the membrane had high replication accuracy and good surface hydrophobicity.Increasing the temperature of the coagulation bath could result in replication distortion of the membrane surface microstructure,and even could cause significant defects.Moreover,the pores of the membrane became large,and the hydrophobic properties,wetting resistance and mechanical properties of the membrane were degraded.The membrane prepared by 4wt%UHMWPE content and 20 ℃ coagulation bath temperature showd good wetting resistance and protein contamination under static test conditions.Due to the small pore size and high hydrophobicity of the membrane surface,the degree of wetting and protein adsorption increased at a slower rate under long-term immersion.In the dynamic test environment,the degree of membrane wetting and protein adsorption increased faster than static adsorption.As the adsorption time and protein concentration increased,the protein adsorption rate increased.