Preparation Of Superhydrophobic And Photocatalytic Self-cleaning Cotton Fabric And Its Properties

In recent years,there have been more and more reports on superhydrophobic cotton fabrics.However,superhydrophobic fabrics currently have shortcomings such as poor washing and abrasion durability,and unrecoverable superhydrophobic property after surface damage.In addition,in daily use,superhydrophobic fabrics will be contaminated by oil molecules from the air or oil secreted by the human body.Due to the hydrophobic interaction between the oil molecules and the superhydrophobic surface during washing,it is relatively difficult to clean away the oily substances.Meanwhile,detergent will remain on the surface after washing,and the continuous accumulation of these organic pollutants will cause the failure of the superhydrophobic function.To this end,this topic combines the photocatalytic effect with superhydrophobic properties,by using ultraviolet light to decompose organic pollutants deposited on the surface of superhydrophobic cotton fabrics,to achieve the purpose of superhydrophobic performance recovery.At the same time,to resolve the problem that the photodegradation of low surface energy substances can cause the deterioration of superhydrophobic properties,heating treatment is used to induce the migration of the low surface energy substances to the top surface and thus to achieve the self-healing of superhydrophobic properties.The specific research content and results are as follows:(1)Preparation and performance study of fluorine-free superhydrophobic photocatalytic self-cleaning cotton fabricTiO2@HDTMS was first prepared through the hydrolysis-condensation reaction by mixing hexadecyltrimethoxysilane(HDTMS)with TiO2 nanoparticles dispersed in water.Then the TiO2@HDTMS was mixed with water-based polyurethane solution(WPU)to prepare the finishing solution.Cotton fabric was then finished with this solution by padding.The optimized finishing solution contained 1.25 g L-1 TiO2,12 g L-1 HDTMS and 24 g L-1 WPU,respectively.The water contact angle(WCA)of the cotton fabric finished using the optimized solution was about 166.2°,and the roll-off angle(WSA)was about 6.2°.The contact angle for various droplets such as milk,coffee,tea stains,vinegar was more than 150°.The waterproof grade could reach level 4.In addition,the coated fabric had excellent washing durability.After 11 times of laundering,the WCA remained at 158.1°.The superhydrophobic property could withstand UV irradiation for 12 h,and recover after further UV irradiation Meanwhile,the finished cotton fabric also had the ability to photodegrade methylene blue and oleic acid and excellent ultraviolet resistance performance(2)Preparation and performance study of fluorine-containing superamphiphobic and photocatalytic self-cleaning cotton fabricPerfluorocage oligomeric silsesquioxane(F-POSS)was first prepared by using perfluorodecyltriethoxysilane as precursor and ethanol as solvent,respectively.Then,fluorocarbon surfactant ST-110 was used to disperse the F-POSS,and the dispersion was added to the ethanol solution containing TiO2 and polytetrafluoroethylene(PTFE)particles to prepare the finishing solution.Cotton fabric was finished with this solution by padding.In an optimized solution,the content of F-POSS,TiO2 and PTFE was 12 g L-1,1 g L-1 and 1 g L-1,respectively.The cotton fabric finished using the optimized solution showed a WCA of 162.5° and hexadecane contact angle(OCA)of 154.0°,taking into account the superhydrophobic and superoleophobic properties,which is mainly due to the long fluorine-containing carbon chain in F-POSS that has low surface energy.Tests on the photocatalytic degradation of methylene blue,oleic acid,surfactant(sodium dodecyl sulfate,SDS)and human secreted oils and fats on this modified cotton fabric showed that it had an excellent photocatalytic degradation ability.It was found that the fluorine-containing superamphiphobic and photocatalytic cotton fabric had stronger photocatalytic resistance than the fluorine-free superhydrophobic photocatalytic cotton fabric,and could still maintain a supehydrophobic state after 36 hours of UV irradiation.This is mainly because the C-F bond has a higher bond energy than the C-H bond,and breaking the C-F bond requires more energy.Moreover,the washing fastness test of the superamphiphobic cotton fabric was carried out.After 20 cycles of washing,UV irradiation to remove surfactant residue and heat treatment for self-healing,it was found that the WCA still reached 160.8°and the OCA was 150.8°,showing that the fabric maintained the superamphiphobic state.In addition,the fluorine-containing superhydrophobic photocatalytic coating has little effect on the breathability of cotton fabrics.The breathability rate of coated fabric was 17.1±0.4 cm3 cm-2 s-1,which is 91.4%of the uncoated cotton.