Surface Functional Modification With In-situ Decorated Hybrid Silica Sol On Fabric

Dyeing and finishing industry is typical on severe pollution, more energy-wasting andcomplicated process, and the textile industry suffers enormous pressure. Therefore, the dyeingindustry is requested to use ecological, energy-saving, emission-reduction, high of additionalvalue and recyclable new technologies. Fabrics should also present non-polluting, functional,intelligent and reusable characteristics after treatment process.According to in-situ decorated sol-gel technology, colorant, silane coupling agent,polyurethane were doped into silica sol to prepare functional sols. dye/SiO₂hybrid sol,dye/CPTS/SiO₂hybrid sol and cationic TiO₂/SiO₂hybrid sol were prepared. After the hybridsol was treated on fabric by spin-coating, layer-by-layer electrostatic self-assembly, and otherprocesses, the color property, fastness and mechanical property of fabric were improved.Meanwhile, the fabric treated by the functional silane coupling agent will present goodhydrophobic and oil repellent property, controlled wettability, anti-bacterial property,anti-ultraviolet behavior, and the mechanical property. This method will shorten the treatingprocess, reduce the pollution and energy, and provide a novel dyeing and printing method.According to the sol types and the coating functionalities, the main conclusions on this topicare listed as following:The preparations of the silica sol doped with colorants are investigated according toin-situ decorated organic-inorganic hybrid technology. Sol properties, including stability andcolor properties are analyzed, and the color and fastness of the treated fabric by the hybridsilica sol also are discussed. In the silica sol doped with organic dye or pigment, themaximum absorption wavelength is consistent with that of the pigment disperse solution.From atomic force microscope （AFM）, there are scraggly micro-surface topographies on thedoped silica film, and the peak sizes in the AFM are inconsistent with the particle sizes of thesilica sols. The color strengths （K/S value） of the coated fabric with doped silica sol are higherthan that of the dye solution or pigment dispersion, and the maximum absorption wavelengthdoes not change. With the dye/SiO₂coating, the dry and wet rubbing fastnesses are increasedby one grade, and the washing change and staining fastnesses are enhanced by half a grade,respectively, while the dry and wet rubbing fastnesses with the pigment/SiO₂coating areincreased by half a grade, and the washing change and staining fastnesses are enhanced morethan half a grade, respectively. These results indicate that the fabric modification withdye/SiO₂presents good color and fastness properties via the wastewater-free and one-stepprocess.Modified silica sols are in-situ prepared by doping hexadec-ltrimethoxysilane,（HTEOS） γ-chloropropyltriethoxysilane （CPTS）, and tridecafluorooctyltriethoxysilane （FAS） to obtainthe hydrophobic or oil repellent coatings on cotton, silk and wool fabrics. Also, a sol-gelderived hybrid silica sol consisting of C.I. Direct Red23dye and inorganic silica issuccessfully synthesized by adding coupling agent CPTS, and via spin-coating, the fabric canobtain good hydrophobicity and color properties. After coated with HTEOS/SiO₂hybrid sol,the fabric could support a subglobose water droplet, and the contact angle is increased to139.8°. The hydrostatic pressure of fabric coated with hybrid HTEOS/SiO₂hybrid sol is4.1KPa, which is significantly higher than that of the control sample （1.8KPa）. The contact angleof the treated fabric with dye hybrid silica sol is increased to112.4°and the contact angle isincreased to131.48°when the fabric was treated with CPTS/dye hybrid silica sol. Thehydrostatic pressure of the cotton fabric coating with CPTS/dye hybrid silica sol is4.5KPaand increased by136.7%compared with that of the untreated fabric. The K/S value （5.15） ofthe dye/CPTS/SiO₂hybrid silica coated cotton fabric is increased by higher30.4%than thatof the control coated sample （3.95）. The dry and wet rubbing fastness with dye/CPTS/SiO₂hybrid silica coating are increased to3and2-3grades, respectively, and the washing changesand stain fastnesses are enhanced to3and3-4grades, respectively. These indicate excellentcolor and hydrostatic properties.An integrated approach to preparing a novel cationic TiO₂/SiO₂hybrid sol withanti-ultraviolet and anti-bacterial performances is investigated by Tetraethoxysilane （TEOS）,Tetrabutyl titanate （TBT） and Polyquaternium. The particle is elliptic from the TEMphotograph, and from FIRT spectrum, the Si-O-Si, Ti-O-Ti and Si-O-Ti bonds are formed inthe cationic TiO₂/SiO₂hybrid coating. From XPS spectra, only the characteristic bands C andO are presented for the original cotton fabric （56.4%C1s and43.6%O1s）. After coated withCSTHS, besides33.2%C1s and48.4%O1s,18.1%Si2p and0.3%Ti2p are confirmed in thecoating. During the UVB （280-320nm） and UVC （200-280nm） wave bands, the lowest URTof the original cotton fabric without washing is higher than7.0%, but the URT of the coatedcotton fabric is almost smaller than5.0%and after washing the URT is lower than6.0%. Thebacteriostatic capabilities of the coated cotton fabric to Gram-negative bacteria E. coli andGram-positive bacteria S. aureus are90.9%and95.2%, respectively, while the antibacterialratios are decreased to61.1%and71.5%during washing respectively, which indicate a goodwashing fastness. The K/S value of the original cotton fabric printed with disperse dye is2.4at520nm wavelength. After modification with CSTHS, the K/S value of the cotton fabric isenhanced to10.1at the same wavelength （520nm）, and the K/S value is sharply increased by320%. The transfer rate of disperse dye is increased to89%from21%. The peaks of the K/Svalue curve for the coated fabric are high and narrow, which indicates that the color vividness is increased relative to the original cellulose fabric. The λmaxof the coated cellulose fabric isunchanged, and it is coincident with the maximum absorption wavelength of the untreatedcellulose fabric, which indicates that the treatment presents little effect on the color hue. Thesharpness and the color strength of the treated cellulose fabric are improved. The wet rubbingfastness is improved from4grade to4-5grade, whereas the tensile property of the treatedfabric was decreased severely.In order to obtain excellent mechanical properties of the treated fabrics during functionalmodification, directional coatings with alkaline SiO₂, TiO₂and acidic cationic SiO₂sol aredesigned and prepared on fabric. The K/S value of the coated fabric via layer-by-layerself-assembly is increased15.8%. Compared to the average ultraviolet radiation transmittance（URT） and bacterial reduction （R） of the control sample, the URT of the treated fiberdecreases from10.6%to1.3%and the anti-bacterial activities to the Gram-negative bacteria E.coli and Gram-positive bacteria S. aureus are increased to95.3%and96.1%, respectively. Forthe treated fabric, the dry and wet rubbing fastness is enhanced by1grade, respectively, thewashing fade rate is decreased to18.2%from31.5%. And the mechanical properties of thetreated fabrics via layer-by-layer self-assembly are better than that with TiO₂/SiO₂hybrid sol.According to the mechanism of the conversion between Ti4+Ti3+under UV lightand dark, modified TiO₂hybrid sol is prepared and coated on fabric to presenthydrophobic-hydrophilic switchable property via UV response. The contact angle of thecoated fabric is121.3°and hydrophobic, but after radiated in UV for18h, the contact angle is0°and hydrophilic. When the radiated fabric is kept in dark place for12h, the contact angle isincreased to93.2°from0°. The difference of the contact angle between93.2°and121.3°iscaused by the polarity of the silane coupling agent. When the fabric is kept in UV and darkplace for10times, the contact angle is switched between0°and94°, and the fabric showshydrophobic-hydrophilic switchable property. From the ultraviolet spectrum, the ultravioletradiation transmittances of the coated fabrics are decreased slightly via radiation UV for18h,whereas, the ultraviolet radiation transmittances are increased when the radiated fabric is keptin dark place for12h. This change of the ultraviolet radiation transmittances verifies themechanism of switchable wettability.Silane coupling agent FAS was in-situ doped in TiO₂sol （TiO₂/FAS hybrid silica sol） toimprove the switchable wettability and the rangeability of contact angle. The anatasecomponent in TiO₂/FAS hybrid silica powder is mixed with rutile component from XRD, andthe crystal component is unchanged in UV light and dark store condition. The switchablecycle of the cotton is84h, while the switchable cycle of the polyester is168h. The TiO₂/FAShybrid silica powder floats on the water surface for its excellent hydrophobicity, and the sample deposits at the bottom of water as the wettability of coated fabric increased via UVirradiation. The irradiated sample floats on water again when it is placed in dark. The coatedcotton and polyester fabric is hydrophilic with UV irradiation, and shifts to be hydrophobic indark. The effect of the fiber morphology on the cycle is more important than that of the fabricconstruction. The water diffusivity and permeable capacity further confirmed the excellentswitchable wettability of coated fabrics by F/TiO₂hybrid sol through UV irradiation orstorage in dark. Some ions, including Ba2+, Mg2+, Fe3+, F-, N3+were doped into the TiO₂hybrid sol via by co-solution method, and the cotton fabric coated with the hybrid sol wasirritated under UV light. The F/TiO₂hybrid sol shortened the damping time of the frontcontact angle and the60°C condition was beneficial to the recover of contact angle in dark.To separate spandex from the waste polyamide/spandex fabric and improve themechanical properties of the cotton fabric, ureido between the isocyanate and diamine wasbroken during heating process, leading to the spandex degradation. After washed with ethanol,the spandex component and nylon component are separated. The spandex component isdissolved in N,N-dimethylformamide （DMF）, and then in-situ doped in silica sol.Nylon/Spandex fabric is treated with dry and opened heating method （DOHM） at220°C for2h, and then washed with ethanol at60°C for60min. The spandex is almost separated andextracted. After coating, the wrinkle resistance and fabric style of the coated the fabric areimproved. The fast wrinkle recovery angles of the treated fabric in warp and weft directionsare improved by27.3%and44.8%, and the slow wrinkle recovery angles in warp and weftdirections are improved by26.0%and28.3%, respectively. With the silica treatment, thecompressing, shearing, tensile strength, bending and washing properties of the fabric are alsoenhanced significantly. The enhancements of these properties are the coatings of the PU/SiO₂hybrid sol on fiber, which is a good pathway for waster spandex recycle.