Preparation And Properties Of Green Superhydrophobic Materials

Superhydrophobic materials have the unique self-cleaning properties like the surface of lotus leaves.Thus,superhydrophobic materials have wide potential applications in self-cleaning,anti-adhesion,anti-icing,and oil-water separation,etc.,and have received great attention in various fields.Various methods have been invented for the preparation of superhydrophobic materials.However,there are some issues of the traditional preparation methods,such as complicated preparation process,high cost,and many pollutive byproducts.In order to solve these issues,here we prepared two kinds of“green”superhydrophobic materials with excellent properties by the spray-coating method and the sol-gel method,respectively,based on food-grade waxes and silanes.Also,the applications of the superhydrophobic materials in anti-adhesion of viscous liquid foods and oil-water separation were studied in detail.A wax suspension was prepared using the food grade paraffin wax by heating dissolution-cooling precipitation-ultrasonication.Superhydrophobic coatings can be prepared by spray-coating the suspension onto substrates.The superhydrophobic coatings showed a high water contact angle of 158.6°and a low rolling angle of 7.8°.In addition,annealing at 40°C for 5 min can enhance mechanical stability of the coatings without changing their superhydrophobicity.In order to study the applications of the superhydrophobic coatings in the anti-adhesion of viscous liquid foods,the suspension was sprayed on various food packaging materials such as PET,PP,and glass to form superhydrophobic coatings.The results showed that the coatings have excellent anti-adhesion properties for liquid foods?e.g.,cola,orange juice,milk and honey?,good chemical stability and high resistance to fatigue bending.Compared with the traditional methods for the preparation of superhydrophobic coatings,the method is simple and green,and is applicable for the other waxes.Polysiloxane aerogels were prepared by the“green”sol-gel method.The polysiloxane hydrogels were prepared by hydrolytic condensation of methyl trimethoxysilane and dimethoxydimethylsilane in and acetic acid aqueous solution in the presence of trace amouts of Na₂CO₃ and surfactant.The polysiloxane hydrogels can be directly dried at 60°C and ambient pressure to obtain the polysiloxane aerogels.The polysiloxane aerogels have a water contact angle of 156°.The polysiloxane aerogels are very strong with a compressive strength of 0.12 MPa at50%strain,and superelastic with small stress loss after 500 compressive stress-strain cycles.Also,the strength and flexibility of polysiloxane aerogels can be controlled by adjusting the contents of Na₂CO₃ and the surfactant.The The polysiloxane aerogels has excellent absorption capability and recycle ability in oil-water separation.The preparation of the polysiloxane aerogels only requires trace amounts of surfactant,Na₂CO₃ and acetic acid.Therefore,this method not only saves raw materials and preparation costs,but also avoids the complicated,time-consuming and pollutive process in the washing and drying of traditional aerogels.In summary,two environmentally friendly superhydrophobic materials have been prepared by a simple and green method.This method solved the defects of conventional preparation methods of superhydrophobic materials,and is helpful for the design of new superhydrophobic materials.The as-prepared green superhydrophobic materials have excellent properties,and are very promising materials in the fields of anti-adhesion of liquid foods and oil-water separation.