| As an environment-friendly method, the hydrophobic finishing of cellulose fabrics by sol-gel method is rapidly developed and become a hot research in recent years. Al2O3sol has been synthesized in nanometer range to introduce roughness on the surfaces by different surface architectures. Moreover, the Al2O3film is high transparency, strong mechanical strength, and satisfactory abrasion and/or scratch resistance.However, the development of non-fluorinated and cheap modifying agents, and cheap precursors for Al2O3films is very important for the fabrication of environmentally friendly coatings on textile substrates. Monocarboxylic acids (CH3-(CH2)n-COOH, n=8-22) or salts, especially stearic acid or stearates, are safe, environmentally friendly, industrial availabile and cheap. They have been known to act also as low surface energy materials for aluminium alloys.In this study, the super-hydrophobic surface with monocarboxylic acids as low surface energy materials and Al2O3as inorganic particles to impart rough surface by sol-gel method was investigated. Aluminum oxide sol was obtained using aluminum nitrate nonahydrate (Al(NO3)3.9H2O) as precursor of Al2O3by precipitation and peptization. Al(NO3)3.9H2O was first precipitated by ammonium and transferred into AlOOH under vigorous stirring. After laundering, the resulting slurry was peptized by using nitric acid as peptizor. The molar ratio of AlOOH to nitric acid to water was1:0.17:100. It has been concluded that the size of nanoparticle in the aluminum sol prepared by changing the precursor (Al(NO3)3.9H2O) concentration did not show no remarkable change (-65nm). The sol prepared under these conditions showed high stability at room temperature. The broad peaks of the Al gel (XRD) indicate that the powders can be considered as amorphous boehmite (AlOOH).Super-hydrophobic surface has been successfully prepared first by dip-coating the nano-Al sol, then the surface of the Al coating was modified with monocarboxylic acids or salts, to gain a thin film through self-assembly. The wettability of treated fabrics was characterized by water contact angle, spray test and hydrostatic pressure test. The paper also investigated the effect on hydrophobicity of hydrophobic agents, Al content of the nano-Al sol, sodium stearate (SS) concentration, baking temperature and time. It has been concluded that sodium stearate is the best hydrophobic agent and has good durability. Hydrophobic treatment by stearic acid or stearates on aluminum surface is based on the spontaneous adsorption and self-assemble of stearate molecules on the aluminum oxide surface. The water contact angle values first increased rapidly with raising the Al content of nano-Al sol and sodium stearate (SS) concentration, then asymptotically reached plateau values at high concentrations. The hydrophobicity of samples increased with raising the baking temperature and time. The results showed that the cotton fabrics treated with1.5%Al sol,20mmol/L sodium stearate and cured at170℃for2min showed excellent hydrophobic properties and UV protection efficiency, the water contact angle could reach146.27°and the UPF value was164.06(UPF rating50+).In order to study the change of fabric surface morphology after hydrophobic finishing, scanning electron microscopy (SEM) was used to observe the surfaces of native cotton and samples treated with different Al content of nano-Al sol and sodium stearate, and to discussed furtherly the effect of the Al content of nano-Al sol on hydrophobicity. It has been concluded that the roughness of fabric surface has great effect to the hydrophobicity from the AFM images. In order to elucidate the interaction between sodium stearate and Al coating, XPS spectra of Cls, Ols and A12p were deconvolved.As a whole, energy was saved and cost was reduced by cheap Al(NO3)3in place of expensive aluminium isopropoxide, and water in place of ethanol in course of Al sol. In addition, sodium stearate is not only cheap and decomposes easily in the environment, but also has excellent hydrophobicity. Thus, it would be enlarged the application of sol-gel technology in the textiles and is possible to industrialize in the future. |
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