Studies On Fluorine-Free Water Repellent Finishing On Cotton Fabrics Via Thiol-Ene Click Chemistry

Water repellent finishing fabrics which firstly used to be uniforms,protective clothing,are now widely used as sportswear,travel wear,travel bags,tents and so on.The traditional perfluorinated finishing agent mainly based on perfluorooctane sulfonic acid(PFOS)or perfluorooctanoic acid(PFOA)has the advantages of excellent thermal stability,chemical resistant,high surface activity and hydrophobic-oleophobic properties.But with the deepening of realization of the defects of PFOA/PFOS,such as hard degradation,environmental persistence and bioaccumulation,to find alternatives and alternative technology has become the research hotspots in recent years.Thus,we propose that water repellent fabrics were prepared by modification with functionalized polyhedral oligomeric silsesquioxanes(POSS)based on click chemistry in this thesis.In this study,cotton fabrics were firstly modified with 3-Mercaptopropyltriethoxysilane(MPTES)to graft thiol reactive groups on the cotton surface.Then,these groups could react with vinyl-POSS and 1-dodecanethiol under UV irradiation to produce hydrophobic surface.The results showed that cotton fabric modified with MPTES successfully,which grafted thiol reactive groups on the cotton fibers.Vinyl-POSS and long chain alkyl hydrosulfide formed a self-assembled layer on the fiber surface during the process.The cotton fabric has been covered by the micronanostructure of hydrophobic layer with water-contact angle of ?149.2°,approaching the level of superhydrophobicity.After 30 cycles of standard washing,water-contact angle still retains ?146.3°,indicating this treatment can be applied to cellulose fibers with durable water repellent properties.In addition,the pretreatment of silica could increase the degree of thiol modification to cotton fabric,and the WCA reached ?153.66° with water repellent finishing.After 30 cycles of standard washing,WCA still remains ?149.23°.We also studied that preparation of alkylfunctionalized silsesquioxanes bearing additional triethoxysilyl groups by way of a photochemical thiol-ene click reaction,and modification of the cotton fibers with these silsesquioxane derivatives.The results of FTIR and NMR showed that,by tuning the equivalents of 1-dodecanethiol,MPTES and vinyl-POSS,POSS derivatives composed of different,but strictly defined,amounts of DDC and TES groups were obtained.The optimum reaction conditions were as follows: room temperature,30 min,500 W UV power,dichloromethane solvent,0.5 wt.% DMPA photocatalyst.The prepared fluorine-free POSS derivatives were applied to cotton surfaces to produce enhanced hydrophobic properties by creating a micro/nanostructure water-repellent layer.The results showed that the WCA value was influenced by the content of the alkyl chain in POSS compounds.These results,obtained after multiple standard washing cycles,also demonstrated that alkyl-POSS bearing additional reactive groups(capable of binding to the surface)can enhance durability.The most effective and durable derivatives appeared to be those containing four DDC groups and four TES groups,which gave rise to surfaces with water contact angles of ?146° and low roll-off angles,leading to considerably higher durability during washing,and represent a promising hydrophobic agent to be used in practical applications.