| SiO2 hydrosol prepared without organic solvent of ethanol and fluoride hydrophobic modifying agent is in accordance with the ecological environment requirement and is the latest research trend of sol-gel hydrophobic finishing of textiles. The SiO2 hydrosol was synthesized using tetraethoxysilane (TEOS) as the precursor and non-fluorinated long-chain silane reagents as hydrophobic modifying agents under the surfactant emulsification. The hydrophobic cotton fabric was obtained by dip-padding process. To endow superhydrophobic property on cotton fabric, a silica coating was directly in-situ deposited on cotton fabric by electrochemically assisted deposition technology with SiO2 hydrosol. And the silane coupling agents was also doped to the silica hydrosol to fabricate the durable superhydrophobic fabric surface.The SiO2 hydrosol with different dosages of TEOS, HC1 and deionized water, different structure and concentration of surfactants was prepared using octyltriethoxysiliane (OTES) as the hydrophobic modifying agent and surfactants as the emulsifiers. The particle size and polydispersity index of SiO2 hydrosol were studied. The results presented that the 67.5 nm SiO2 hydrosol with polydispersity index of 0.36 was obtained under the optimum conditions of 0.4 g/L SDBS,6.0 TEOS,3 mL HCl and 100.0 g deionized water. FT-IR spectra confirmed that SiO2 nanoparticles were successfully prepared via sol-gel emulsion polymerization method and and non-fluorinated alkyl long-chain of hydrophobic modifying agents had been bonded onto the SiO2 nanoparticle surface.Hydrophobic cotton fabric was fabricated from the SiO2 hydrosol prepared via sol-gel emulsion polymerization method by dip-padding process. The finished cotton fabric showed good hydrophobicity with water contact angle of 150.8°and spray rating of 90 under the optimum conditions of 6.0 TEOS,0.4 g/L SDBS,3 mL HC1 and 8 wt% isooctyltriethoxysiliane (iso-OTES). However, the finished cotton fabric exhibited poor washing durability of hydrophobicity. Through 10 washing times, the water contact angel of finished cotton fabric was merely 104.9° with the spray rating of 50. The whiteness and mechanical property of cotton fabric coated with SiO2 hydrosol via dip-padding process were changed slightly, while the breathability was weakly decreased, which did not affect the wearing performance.To obtain superhydrophobic cotton fabric at the fluoride-free condition, a homogeneous and dense film was directly in-situ deposited on cotton fabric by electrochemically assisted deposition technology with SiO2 hydrosol. The effects of deposited voltage, deposited time, surfactant SDBS concentration and hydrophobic modifying agents with different structure and concentration on the hydrophobicity of deposited cotton fabrics were investigated. The contact angle of the deposited cotton fabric reached about 157.0° exhibiting superhydrophobicity with deposited voltage of 15.0 V, deposited time of 10 min, surfactant SDBS concentration of 0.4 g/L. For hydrophobic modifying agents with different structures, the water contact angles of deposited cotton fabrics increased gradually with increase in the concentration of hydrophobic modifying agents up to 6 wt% and then almost remained constant thereafter. The water contact angle values of deposited fabric samples functionalized from SiO2 hydrosol doped with 8 wt% OTES, dodecyltriethoxysiliane (DTES) and iso-OTES were 157.7°,158.6° and 162.3°, respectively. In terms of the deposited fabric sample functional ized from SiO2 hydrosol doped with 8 wt% iso-OTES, the larger water contact angle value was due to the introduction of the non-polar and hydrolytically stable of-Si(CsH17) groups on the cellulose substrate surface.The mechanical properties of deposited cotton fabrics from SiO2 hydrosol via electrochemically assisted deposition were changed. The breaking strength and breaking strength rate of deposited fabric in warp were decreased by 7.7% and 14.8%, while the breaking strength and breaking strength rate in weft changed little. The whiteness of deposited cotton fabric showed slight change, while the breathability was decreased to 105.6 min.s-1 from 129.4 mm.s-1, which did not affect the wearing performance. XPS results showed that there was Si element on the deposited cotton fabric and a large increase of the C/O ratio from 1.84 to 2.85, which confirmed that the SiO2 hydrosol modified with long alkyl group was deposited onto cellulose fibers. Through soap washing, the contact angle of the deposited cotton fabric was 151.1°, and the hydrophobic property was still good. However, the water contact angel of deposited cotton fabric was merely 104.9° with 10 washing times. The results presented the deposited cotton fabric exhibited poor washing durability of hydrophobicity.In order to improve the washing durability of hydrophobicity of deposited fabrics, the silane coupling agents with different structures were used to dope the silica hydrosol during the electrochemically assisted deposition process. The results showed that even the addition of γ-mercaptopropyltriethoxysiliane (MPTES) decreased the water contact angle from 162.3° to 154.2°, the washing durability of hydrophobicity of deposited fabric was improved with the MPTES as the silane coupling agent. Especially, for the fabric sample functionalized from silica hydrosol doped with 1.0 wt% MPTES, the water contact angle still remained 130.0° after 20 washing times. The results of SEM, XPS and TGA demonstrated that with the addition of silane coupling agent MPTES, the adhesion between cellulose substrate and silica gel coating was enhanced and the washing durability of hydrophobicity of deposited fabric was improved. |
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