Study On The Superhydrophobic Modification Of Cotton Fabric By Enzymatic Caffeic Acid

Natural fiber is an important source of traditional textile fibers.As one of the main natural fibers,cotton fiber is rich in sources and naturally renewable and biodegradable.It is widely used because of its softness and skin friendliness,good moisture absorption and air permeability.With the development of science and technology,textile materials gradually tend to be functionalized,and superhydrophobic functional textile materials are one of the research hotspots today.At present,there are some shortcomings in the preparation of superhydrophobic cotton fabrics,such as complex process,high equipment requirements,high industrialization cost,expensive hydrophobic finishing agent and pollution of fluorine-containing finishing agent.At the same time,during the use of superhydrophobic textile materials,their micro-nano rough structures are easily destroyed or the hydrophobic coating is not firmly combined with the substrate,resulting in poor solvent resistance,washing resistance and wear resistance of superhydrophobic materials.These deficiencies need to be solved urgently.Guided by the application of self-cleaning and oil-water separation,this paper develops an environmentally friendly and durable superhydrophobic cotton fabric modification method to prepare superhydrophobic modified cotton fabric for oil-water separation,and then explores its related properties.The main research contents and conclusions are as follows:The hydrophobic modification of cotton fabric was carried out by using laccase to catalyze the polymerization of caffeic acid and chelate deposition with Fe²⁺to construct micro-nano rough structure on the surface of cotton fiber.Characterized by contact angle,the modification effects of laccase-catalyzed caffeic acid polymerization and caffeic acid self-oxidation polymerization on cotton fabrics were compared.The effects of various process conditions on the hydrophobic properties of modified fabrics were investigated by single factor method.The results showed that the laccase catalytic system not only improved the polymerization rate of caffeic acid,but also showed better hydrophobic properties.Under the conditions of caffeic acid concentration of 3 mg/m L,laccase concentration of 0.75 U/m L,Fe²⁺concentration of 12mg/m L,reaction temperature of 70°C and reaction time of 2 h,the contact angle of the prepared modified cotton fabric（LCF）could reach 153.4°and the rolling angle was 30.6°.It shows good hydrophobicity without using hydrophobic finishing agent,but has great adhesion to water.After 1000 friction and 20 washing cycles,the contact angle decreases by 10.39%and 10.85%respectively.Under strong acid and alkali test conditions,the contact angle decreased by 12.36%and 12.88%,respectively,reflecting good durability.In order to improve the hydrophobic durability stability of superhydrophobic cotton fabrics and reduce the rolling angle to meet the practical application requirements,a low surface energy hydrophobic finishing agent hexadecyltrimethoxysilane（HDTMS）was introduced to modify LCF modified cotton fabrics to form a composite structure of superhydrophobic cotton fabrics（HDTMS@LCF）.The effects of HDTMS concentration and drying temperature on the hydrophobic properties of superhydrophobic modified fabrics were discussed.When the HDTMS concentration was 1%and the drying temperature was 120°C,compared with the LCF modified cotton fabric,the contact angle increased from 153.4°to 164.6°,and the rolling angle decreased from 30.63°to 6.75°.Compared with LCF modified cotton with only rough structure,the introduction of HDTMS improves the hydrophobicity and makes the superhydrophobic composite structure closer.The prepared HDTMS@LCF superhydrophobic cotton fabric was tested.The results showed that the contact angle of the modified fabric remained within 7%after 1000 friction cycles,20 washing cycles and strong acid-base conditions tests.It had good acid and alkali resistance,friction resistance and water washing hydrophobic stability.It showed good self-cleaning performance in self-cleaning test,and the oil-water separation efficiency remained at about 95%after 15 times of light and heavy oil separation tests,showing good oil-water separation performance.In order to improve the oil-water separation performance of superhydrophobic fabric and realize the controllable size of rough structure,the metal organic framework ZIF-8 was introduced to construct the micro-nano structure on the surface of cotton fabric.Laccase was used to catalyze the polymerization of caffeic acid and ethylenediamine was used to form an aminated polycaffeic acid coating.ZIF-8 crystals were grown in situ on the surface to form a micro-nano-scale rough structure to prepare a modified cotton fabric（LCE-ZIF）,and HDTMS was used for low surface energy modification to prepare a superhydrophobic cotton fabric（LCE-ZIF@HDT）.By controlling the molar ratio of 2-methylimidazole to Zn²⁺to change the size of the rough structure,the effect of molar ratio on the hydrophobic properties of superhydrophobic cotton fabrics was investigated.The results show that when the molar ratio of 2-methylimidazole to Zn²⁺is 15:1,the prepared superhydrophobic cotton fabric has a contact angle of 164.8°and a rolling angle of 5.84°.SEM,FTIR,EDS,XPS and XRD tests showed that ZIF-8 and HDTMS were successfully introduced on the surface of cotton fabrics.The prepared LCE-ZIF@HDT was tested for 1000 friction cycles,20 washing cycles and strong acid and alkali conditions.The results showed that it had good superhydrophobic and durable stability,and showed good self-cleaning performance in self-cleaning tests.After 15 oil-water separation tests of light oil and heavy oil,the oil-water separation efficiency was still higher than 97%,which had good potential in self-cleaning and oil-water separation applications.