Preparation Of Oxidized Chitosan/TiO₂ Composite Nanomaterials And Study On Their Modification Of Cotton Fabrics

Due to the increasing depletion of fossil resources such as oil and coal,how to effectively use natural fiber resources to achieve the"carbon peaking and carbon neutrality goals",has become a hot research topic.Cotton as the main natural cellulose fibres,because of its soft feel,moisture absorption and breathability,warmth and comfortable to use,play an important role in the field of textile materials,but cotton fibres and their products in the wearing,washing process easy to shrink,antibacterial poor,single function,low added value and other problems seriously plagued the sustainable development of the cotton industry.On the basis of maintaining the excellent natural properties of cotton fibres,functional modification of cotton fibres and their products to expand their applications and enhance the added value is urgent.The main research results are as follows:（1）Selective oxidation of chitosan at C2 and C3 positions by sodium periodate（Na IO₄）and selective oxidation of chitosan at C6 position by HNO₃/H₃PO₄-Na NO₂oxidation system were used to obtain water-soluble oxidized chitosan（OCS）,and then nano-oxidized chitosan（Nano-OCS）was prepared by ionic gelation method at OCS mass concentration of 0.4%,H₂O₂ degradation OCS time 3 h,p H value of reaction solution 4.0,Span-80 concentration 2 g/L,TPP concentration 0.2 g/L,and reaction temperature 25℃,Nano-OCS particles with average particle size of 140.5 nm,polydispersity coefficient PDI of 0.233,and Zeta potential of 35.13 m V were prepared,and their effects on Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）were observed.The minimum inhibitory concentrations（MICs）for E.coli and S.aureus were 0.16 mg/m L and 0.08 mg/m L,respectively,which were 8 times higher than chitosan and 4 times higher than OCS.（2）In order to increase the application range of oxidized chitosan,anatase Ti O₂sol and Nano-OCS were mixed in a mass ratio of 1:8 to prepare OCS/Ti O₂ composite nanomaterials with an average particle size of 198.8 nm,a PDI of 0.274,and a Zeta potential of 38.87 m V.The MICs of composite nanomaterials for E.coli and S.aureus were 0.08 mg/m L and 0.04 mg/m L,and the inhibitory activities were both twice as high as those of Nano-OCS.Compared with pure Ti O₂,the specific surface area of composite nanomaterials is as high as 67.11 m²/g,the bandgap energy is reduced to 2.81 e V,and the response activity to visible light is improved;Using methylene blue（MB）dye as a simulated pollutant,the degradation rate of MB by the composite nanomaterial reached98.72%after 120 minutes of UV irradiation.After 5 cycles of experiments,the degradation rate of MB dye remained at 80.03%;In the photodegradation dyes of OCS/Ti O₂ composites,superoxide radical（·O₂^-）is the active substance that plays a major role,while hydroxyl radical（·OH）and photogenerated hole（h⁺）play a secondary role in degradation.（3）By grafting cotton fabric with Nano-OCS to endow it with functionality,the grafting rate of Nano-OCS modified cotton fabric reached 6.03%under the conditions of Nano-OCS mass concentration of 0.4%,dispersion p H value of 4.0,grafting reaction temperature of 60℃,and reaction time of 2 h.FTIR analysis showed that Nano-OCS formed a semi acetal chemical binding with cotton fibers.SEM showed that Nano-OCS particles were more uniformly bound on the surface of cotton fibers.XRD and TG/DTG analysis showed that the crystal structure of modified cotton did not change significantly,and the thermal stability of the modified fabric was improved.The breaking strength of modified cotton fabric increased by 7.21%,the wrinkle recovery angle increased by 18.64%,the moisture regain slightly increased,the whiteness remained basically unchanged,and the breathability did not change much.Cotton fabric has good wearing performance.After 50 washes,the antibacterial rates of modified cotton against two test strains,E.coli and S.aureus,were maintained at 92.38%and93.27%,respectively,demonstrating good antibacterial and washable properties.（4）Using OCS/Ti O₂composite material modification to enhance the functionality of cotton fabric,the grafting rate of modified cotton fabric reached 4.74%under the conditions of OCS/Ti O₂composite nano material mass concentration of 0.6%,dispersion p H value of 4.0,grafting reaction temperature of 60℃,and reaction temperature of 3 h.Structural characterization shows that OCS/Ti O₂ composite nanoparticles have been grafted onto the surface of cotton fibers,and the crystalline configuration of the modified cotton fabric by composite nanomaterials has not changed significantly.The thermal stability of the modified fabric has slightly increased.The performance test showed that the breaking strength of the modified cotton fabric increased by 13.79%,the wrinkle recovery angle increased by 25.02%,the moisture regain slightly improved,the whiteness increased by 10.06%,and the permeability decreased slightly（8.35%）;After 50 washes,the antibacterial rates of the composite nano material modified cotton against E.coli and S.aureus were 94.14%and 95.28%,respectively.The antibacterial durability was good,and the UV resistance UPF value of the modified cotton fabric reached 124.85,while the UVA transmittance decreased to 2.79%.