Preparation And Properties Of Multifunctional Superhydrophobic PI Nanofiber Composite Membranes

Superhydrophobic material refers to a class of materials whose static contact angle with water droplets is greater than 150°and rolling angle is less than 10°.Due to the superhydrophobic materials have many excellent properties,such as waterproof,anti-ice,anti-corrosion and self-cleaning,so they can be used in industrial production,daily life,national defense,aviation and etc.,which shows that the research of this kind of materials has certain practical significance.However,the current preparation methods of superhydrophobic materials have some limitations,such as complex process,harsh reaction conditions,high selectivity of substrate and high requirements of reaction on instruments and equipment.The preparation method of superhydrophobic materials used in this paper has certain universality,which is suitable for inorganic materials,organic materials and metal materials,and the experimental reaction conditions are mild and the operation is simple.At the same time,the polyimide selected in this paper has the characteristics of high mechanical strength and high temperature resistance,so that it can be used in some special occasions,such as membrane distillation under high temperature.It mainly includes the following contents:（1）Polyimide（PI）nanofiber membrane was prepared by electrospinning,and then micro-nano structures were constructed on the fiber surface by using the structural properties of polyaniline（PANI）,and finally 1H,1H,2H,2H-perfluorodecyl triethoxysilane（PDTS）layer was generated on the composite fiber surface to achieve the effect of reducing the surface free energy of the membrane.The experimental results showed that this method can prepare the superhydrophobic film and increase the contact Angle from about 124°to about 150°of pure PI,thus achieving the superhydrophobic effect.（2）A layer of polydopamine（PDA）was generated on the surface of PANI/PI nanofibers by utilizing the adhesion of dopamine（DA）on the basis of constructing micro-nanostructures.Then the superhydrophobic PDTS/PDA/PANI/PI（PI-c）nanofiber composite membranes were prepared by cross-linking between hydroxyl group in polydopamine and active hydroxyl group transformed by alkoxy group in PDTS.The experimental results showed that the modified hydrophobic film has excellent superhydrophobic properties,the contact Angle is about 158°,the adhesion to water droplets is low,the film surface is not easy to wet,and has the function of self-cleaning.And it has excellent separation effect on oil-water mixture and emulsion.It can also be used for direct contact membrane distillation（DCMD）.After 300 min,the salt retention rate is still up to 98%.（3）By means of electrostatic adsorption,titanium dioxide（Ti O₂）nanoparticles were adsorbed on the surface of PANI/PI fiber,and then Ti-OH was crosslinked with the active hydroxyl group transformed by the alkoxy group of PDTS to prepare the superhydrophobic PDTS/Ti O₂/PANI/PI（PI-3）membrane.The experimental results showed that the modified hydrophobic film has excellent superhydrophobic properties,the contact Angle is about 162°,and it has the function of self-cleaning.In addition,it can be applied to direct contact membrane distillation,which,even after 480 min,the membrane flux is still stable at 10 L?m^-2?h^-1,and the salt rejection rate is more than99%.At the same time,it also has outstanding effect in corrosion prevention.