Preparation Of Superhydrophobic And Uv-Blocking Cotton Fabrics Based On Nano-ZnO

Since the discovery of the lotus effect, there have been efforts to develop materials with superhydrophobicity because of its excellent performance. In this paper, nano-ZnO was prepared by chemical bath deposition method and loaded on the cotton substrates with one-step processing. Then stearic acid was used to treat the ZnO roughed cotton fabric for superhydrophobic surface. Due to the characteristic of the absorption and shielding ultraviolet of nano-ZnO, UV-blocking function was also introduced to the treated cotton fabrics.The wettability of cotton fabrics treated with several different zinc sources and alkali agents was compared to find the optimal reactants. The result showed that zinc nitrate treated sample gained the best superhydrophobicity among zinc acetate, zinc nitrate, zinc chloride and zinc sulfate. And among hexamethylenetetramine, urea, ammonia and ammonium carbonate, the ammonia treated sample showed the best superhydrophobicity. The water contact angle (WCA) of cotton fabric treated with zinc nitrate and ammonia is149.08±1.06°. Four processes G1-G4to prepare superhydrophobic cotton fabric were designed and compared according to the wettability of the samples. The result showed that the sample treated with G3method have not only excellent superhydrophobicity but also short process time.The wettability and UV-blocking properties of the samples treated by different processed conditions, such as zinc ion concentration, concentrated ammonia volume, deposition temperature and time and stearic acid concentration were investigated. The results showed that the WCAs first increased rapidly and then remained unchanged with the increase of zinc ion concentration. Between the concentration of zinc ion0.1-0.3mol/L, the WCAs of the samples were all around145°, which showed the superhydrophobic effect was in the a stable state. With the increase of the volume of concentrated ammonia, the WCAs increased gradually except for4mL, then remained substantially unchanged. Superhydrophobicity of the sample kept no changes with the WCAs all above145°when the ammonia volume greater than8mL. As deposition temperature was gradually raised, the WCAs first increased and then decreased with the maximum taken at70℃. With prolonging the deposition time, the WCAs first increased and then remained stable aftetr60min. With the increase of the concentration of stearic acid, the WCAs increased dramatically and then slowly with the WCAs of150±0.83°at20mmol/L. And5uL drop of water could not stand on the surface of fabric treated with50mmol/L stearic acid.The research of UV resistance showed that the UV transmittance of raw cotton and stearic acid treated cotton were essentially coincident with UPF values of4.72and4.82, respectively. UPF values of the samples gradually increased with the increase of the concentration of zinc ion and had the maximum of46.36at0.4mol/L. For different ammonia volume treated samples, the best anti-UV function was achieved at4mL with UPF value of81.57. The UPF values remained almost unchanged between8-16mL. With the increase of deposition temperature, the UPF values of samples increased and reached the maximum at90℃. The anti-UV performance of the samples became better with increase of the deposition time. As stearic acid concentration increased, the UPF values of samples slowly increased with the maximum UPF value of35.39at50mmol/L.XRD analysis indicated that the sediment on the cellulose fibers after deposition processing was revealed to be Zn(OH)2and a small amount of ZnO. However, Zn(OH)2on the fabric was completely converted to ZnO after stearic acid processing and curing. SEM analysis showed that the ZnO deposited on the fabrics existed in the form of flower-like clusters in micro scale, while each flower-like cluster is constituted by a large number of needle-like nano ZnO. After treated with stearic acid, flower-like clusters were obviously covered with a layer of stearic acid.The results also showed that the tensile strength and tear strength remained unchanged. Whiteness of the treated samples was slightly increased. However, the washing durability of the treated cotton fabrics was not good for wearing.