Preparation And Characterization Of Self-cleaning Meterials Based On SiO₂Areogel

Self-cleaning materials refers to materials who can maintain its cleaning surface in thenatural conditions, removing stains automatically without artificial cleaning, which greatly reducethe cost of cleaning. The preparation of self-cleaning materials is mainly based onsuperhydrophobic and superhydrophilic principle.Chose the methyl silane as precursor system for the preparation of SiO2gel particles with aserial of good properties, such as hydrophobicity, large specific surface area, high stability, highporosity, small density, low thermal conductivity,which has extensive application value in variousfields. But it is easily polluted with oil in the process of application, effecting the cleaning effect.Therefore, two methods were chosen to prepare the self-cleaning material based on the structureand the superhydrophobicity of SiO2aerogel in this paper. The main research contents andconclusions are as follows:(1)The preparation of self-cleaning fabric with superhydrophobic and superoleophobicproperties and the testing of self-cleaning properties:SiO2aerogel was prepared using MTMS as the precursor, oxalic acid and ammonia as thecatalyst via sol-gel technique and atmospheric pressure drying technology. In order to improve thefastness properties in reality, GPTMS and APTMS were chosen for modification in the sol gelprocess. At last, it turned to be with epoxy group and amino group respectively. The study foundthat SiO2aerogel still had nano porous network structure after modification.The cotton fabric with pretreatment was dipped in chitosan solution, and its surface wascovered with a large number of amino groups. After dried in natural air, it was pad in SiO2gelparticle dispersion with epoxy and amino groups in turn, finally PFTMS was sorted to the fabricsurface with CVD or soaking method. With such finishing, the cotton fabrics’ contact angle ofwater droplets, cooking oil and hexadecanewereup to164°,157°and162°respectively, showing excellent self-cleaning performanceand rubbing fastness properties. Even after12500times, itscontact angle still around150°. Contact with the CVD method, the rubbing fastness was slightlybetter with soaking method after modification.(2) The preparation of self-cleaning materials with photocatalytic and superhydrophobicproperties, and its application on cotton fabric.Multiphase semiconductor photocatalyst TiO2is famous for non-toxic non-polluting, highefficiency, simple operation, mild reaction conditions, wide scope of application in the field ofself-cleaning. But some problems exist, such as poor adsorption performance, agglomeration,recovery and high cost. Therefore, this article selected the SiO2as the carrier of TiO2. Ascomposite photocatalyst, SiO2-TiO2had a large specific surface area, high oxidation activity,strong adsorption, easy to recycle, etc.Using MTMS as precursor system for the preparation of SiO2gel particles, and choosingTiCl4and benzyl alcohol under the condition of low temperature to growth TiO2in its suspension,composite material SiO2-TiO2was prepared. The study found that SiO2-TiO2-A and SiO2-TiO2-Bthe two samples who loaded with different content of TiO2had both anatase type structure and astrong light absorption in the ultraviolet area. Their grain sizes were4.0nm and3.5nm and thespecific surface area were341.7m2/g and379.0m2/g respectively.SiO2aerogel has a large number of-CH3groups, with nano porous network structure,whichis superhydrophobic, and SiO2has a big specific surface area, which is easy to adsorp organiccontaminants. When TiO2with small size and perfect crystallization was distributed on the surfaceof SiO2,which was helpful to the photocatalytic degradation performance of TiO2. With traditionalleaching-rolling-drying method, the water contact angle of cotton fabrics was up to160°. Oncethe cotton fabric was polluted with oleic acid, the cotton fabric transmitted fromsuperhydrophobicity to superhydrophilicity and its water contact angle would be less than5°, butit could recover to around160°under the irradiation of uv light,which showed excellentself-cleaning and reusable performance.