Preparation Of Superhydrophobic And Oleophobic Surfaces With Inorganic Nanoparticles/organic Water And Oil Repellents

Most petroleum-based polymers are non-biodegradable and difficult to recycle,creating a serious environmental problem.With the increasing awareness of environmental protection,the demand for environmentally friendly materials is also increasing.As a biodegradable material,paper has a very broad application prospect,and"paper instead of plastic"has become an important development trend.However,because of its porous structure and the natural hydrophilic nature of the fibers,paper is highly hygroscopic.When the moisture in the environment is absorbed by unmodified paper packaging materials,the physical and mechanical strength of paper such as tensile strength and breakage resistance properties will be reduced.The emergence of superhydrophobic paper offers an effective solution to this challenge,as it can greatly improve the paper’s resistance to wetting and water,while the paper is also endowed with properties such as excellent self-cleaning and stain resistance.There is no doubt that there is an urgent need for the superhydrophobic modification of cellulose-based materials and their expansion for high value-added applications.Firstly,superhydrophobic coatings were prepared from stearic acid-modified chitosan and titanium dioxide nanoparticles of different particle sizes,and superhydrophobic papers with a water contact angle of 160°were prepared by attaching the micro-and nanocomposite particles to the paper substrate by dip-coating.The properties such as chemical composition,crystallinity,surface morphology of the paper and hydrophobicity of the particles before and after modification were investigated using FT-IR,XRD,XPS,SEM,EDS and contact angle tests.The effect of the ratio of different components on the interfacial wetting performance was also investigated.When the ratio of Ti O₂:CS:SA was 7:1:5,the hydrophobic paper had good anti-wetting performance and the contact angle was 151°,which could achieve superhydrophobic effect;when the compound ratio of 5-10 nm and 40 nm Ti O₂particles was 7:3,the anti-wetting performance was further improved and the contact angle could reach 160°.In addition,the superhydrophobic coating also exhibits excellent self-cleaning,liquid repellency,easy repair and organic solvent antifouling properties.Next,superhydrophobic and oleophobic coatings were prepared by hydrolytic condensation of tetraethyl orthosilicate（TEOS）and octadecyltrichlorosilane（OTS）as organic components and titanium dioxide nanoparticles as inorganic components,and the organic-inorganic hybridization was achieved by hydrolytic condensation under alkaline conditions.To study the microscopic morphology and chemical composition of the manufactured coatings by SEM,XPS and FT-IR.The effects of the amount of titanium dioxide nanoparticles,hydrolytic condensation time,and the ratio and amount of organosilanes on the interfacial wetting properties of paper were investigated to obtain the best process for preparing superhydrophobic and oleophobic coatings.When the nano-titanium dioxide addition is 0.16%,the reaction time is 6 hours,the volume of organosilane TEOS and OTS is 1:2 and the silicone addition is 23%,the water contact angle of the coating surface reaches 159°±1.5°,the rolling angle is 3.5°±0.5°,the contact angle of glycerol reaches 155°,the contact angle of glycol reaches 142°,the coating has superhydrophobic highly oleophobic effect.The coating is superhydrophobic and highly oleophobic.The coating also exhibits low adhesion to water,excellent self-cleaning ability and corrosion resistance.Finally,superhydrophobic emulsions were prepared by using nano-wollastonite particles to construct rough micro-nanostructures and degradable wax emulsions as low surface energy substances,which were coated on the paper surface and heat-treated to obtain superhydrophobic papers with wear-resistant properties.When the filter paper was coated with the emulsified wax low surface energy emulsion,its surface changed from hydrophilic to hydrophobic and the contact angle reached 120°.And after the superhydrophobic wax emulsion was coated and heat treated,the contact angle of the coated surface was as high as 157°with a rolling angle of 3.5°.This low-cost and simple coating is self-cleaning for a wide range of food liquids and exhibits excellent resistance to repeated bending and multiple abrasion damage（e.g.severe sandpaper polishing）while maintaining its hydrophobicity.In addition,the coating can be applied to the inner surface of various food packages to reduce or even eliminate liquid food residues.