Biomimetic Preparation And Characterization Of Superhydrophobic Surface On Cotton Fabrics

With the rapid developments of micro/nano-technologies, people have learned much about microstructures from natural materials, and are trying to find out approaches to mimic these natural materials. The demands of tailored surfaces, such as superhydrophobic surface, also motivate people to explore the physical and chemical mechanisms of superhydrophobicity in nature. Superhydrophobic surface has attracted tremendous interest in both fundamental researches and practical applications.Recently, as markets in leisure and outdoor sporting textiles have been expanded, the needs for superhydrophobic fabrics have continuously increased. Cotton has always been the principal clothing fabric due to its attractive characteristics such as softness, comfort, warmness, biodegradation, and low cost. However, the abundant water-absorbing hydroxyl groups on cotton surfaces make the fabrics absorbent and easily stained by liquids. Therefore, additional finishes are required to impart superhydrophobicity and self-cleaning properties on cotton fabrics. In our study, we prepared superhydrophobic cotton fabrics by sol-gel method and self-assembly based on inorganic-organic hybrid material.The main contents and results of the work are as follows:(1) Superhydrophobic cotton fabric was successfully obtained first by dip-coating the silica sol, and then the fabric was modified with fluorinated alkylsilane (G502B) through self-assembly methods. Silica sols with different sizes were prepared by controlling the concentration of ammonia and the reaction time. The experimental results indicated that the finished cotton showed superhydrophobicity with water contact angle of 155°. Scanning electron microscopy was used to observe the cotton fabric surfaces treated with and without silica sol.(2) A superhydrophobic ZnO nanorod film on cotton substrate was fabricated via a wet chemical route and subsequent modification with different carboxylic acids (C8-C18). The as-obtained cotton sample was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), respectively. The wettability of the cotton fabric sample was also studied by contact angle measurements. The effects of ZnO features, different carboxylic acids and different pre-wetting time on contact angles were investigated. The results showed that the cotton fabrics modified with stearic acid exhibited best superhydrophobicity with a high contact angle of 163°for 6μL water droplets. It was shown that the proper surface roughness and the lower surface energy both played important roles in creating the superhydrophobic surface.(3) Water repellency and ultraviolet (UV) protection are desirable properties for textiles. In this chapter, the cotton fabrics were first treated with CeO2 sol and then modified with a layer of dodecafluoroheptyl-propyl-trimethoxylsilane (G502). The as-obtained cotton sample was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and fourier transformation infrared spectroscopy (FTIR), water contact angle measurement, and UV-vis spectrophotometry, respectively. The modified cotton surface not only exhibited robust superhydrophobicity with a high contact angle of 158°and low roll-off angle of 14°for 5μL water droplets, but also rendered excellent protection against UV radiation because of incorporation of CeO2 particles.