Effect of alkyl SiO2 dipping solution on the superhydrophobic modification of PTFE membranes
Hydrophobic polytetrafluoroethylene(PTFE)membrane has a wide application prospect in membrane contactor processes such as membrane distillation and membrane absorption.In this research,a colloidal solution of silica(SiO2)nanoparticles was prepared by sol-gel method,using pure water,anhydrous ethanol,ammonium hydroxide,and tetraethyl orthosilicate(TEOS)as raw materials.Then,with methyl triethoxysilane(MTES)used as the organic modifier,SiO2 nanoparticles were modified on the surface to prepare the alkyl SiO2 dipping solution.This research investigated the effect of raw material ratio on the particle size of SiO2 nanoparticles,along with the effects of preparation time and mass ratio of MTES to TEOS on the hydrophobic modification of PTFE film were further investigated.The results show that the size of SiO2 nanoparticles can be reduced by increasing the amount of ammonium hydroxide and TEOS,and increasing the ratio of pure water to anhydrous ethanol.Extending the preparation time or increasing the mass ratio of MTES to TEOS could increase the contact angle of the membrane surface at first and then decreased.When the mass ratio of raw material was 13.32∶11.92∶1.92∶1(pure water,anhydrous ethanol,ammonium hydroxide,and tetraethyl orthosilicate),the preparation time of alkyl SiO2 dipping solution was 24 h,and the mass ratio of MTES to TEOS was 3∶1,the surface contact angle of the modified PTFE membrane reached 156°,and the superhydrophobic effect was significant.
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