Synthesis Of Nano-SiO₂/Fluorine-silicon Polyacrylate Emulsion And Its Application In Amphiphobic Finishing Of Cotton Fabric

Cellulose is a natural polymer compound,and has the characteristics of biocompatibility and biodegradation.The fabric made from cellulose has excellent skin affinity,comfort and degradability,so it is more and more favored by people.However,due to the strong hygroscopic property of cellulose,it is vulnerable to the erosion of water-based stains,and easy to breed bacteria in the humid environment,thus reducing the service life of fabric.Therefore,it is necessary to finish the hydrophobic and oleophobic functions of the cellulose fabric,which not only endows the cellulose fabric with certain functionality,but also improves the added value of the product.Fluorinated polyacrylate emulsion is widely used in amphiphobic（hydrophobic and oleophobic）finishing because of its low surface energy and easy film formation.The organic-inorganic nanohybrid material combines the low surface energy of fluorinated polyacrylate with the use of inorganic nanoparticles to construct rough structures on the substrate surface.The synergistic effect of the two materials gives the material better amphiphobic properties.In addition,in order to reduce the use of fluorinated monomers,usually using a core-shell structure of fluorinated acrylate emulsion,the shell phase of the fluorinated monomers will be better concentrated to the film surface,effectively improve the utilization of fluorinated groups,effectively reduce costs,and reduce environmental pollution.In this paper,methyl methacrylate（MMA）,lauryl methacrylate（LMA）,dodecfluoroheptyl methacrylate（DFMA）,vinyl triethoxysilane（KH151）,octadecyl methacrylate（SMA）and KH570 modified nano-Si O₂ as raw materials,nano-Si O₂/fluorine-silicon polyacrylate emulsion with core-shell structure was synthesized.The modified nano-Si O₂ has double bonds,and its surface continuously reacts to form organic polymer,so as to wrap nano-Si O₂ to form core phase and construct organic and inorganic composite network.At the same time,the long alkane SMA was introduced into the shell phase to cooperate with fluorinated monomer DFMA,which made the fluorine-containing groups more orderly and the crystallinity of fluorine units improved.Then the cotton fabric was finished by padding and spraying respectively,and the two finishing processes were compared and analyzed.Finally,the properties of the amphiphobic fabric were discussed,and the amphiphobic system of cellulose fabric was improved.The specific work is as follows:（1）Synthesis of composite emulsionNano-Si O₂/fluorine-silicon polyacrylate emulsion（hereinafter referred to as"composite emulsion"）with core-shell structure was prepared by pre-emulsification semi-continuous in situ emulsion polymerization,and the reaction mechanism of the emulsion was analyzed combined with the polymerization process.The static stability,emulsion monomer conversion and coagulation rate of shell phase pre-emulsion and composite emulsion were used as indexes to evaluate the emulsion stability,and the amphiphobic function of composite emulsion was evaluated by the contact angle between water and oil of latex film.From the stability and function of composite emulsion,the effects of pre-emulsification technology,emulsifier type,fluorine monomer and nano-Si O₂ dosage on the properties of emulsion were investigated.The results showed that the optimum reaction conditions were pre-emulsification with high-shear homogenizer,emulsification with 8000 r/min for 30 min,anion reactive emulsifier DNS-86 with3 wt%,DFMA with 20 wt%and Si O₂ with 1 wt%.（2）Study on the properties of composite emulsion and its latex filmFirst,the basic properties of the composite emulsion were tested.The micellar particle structure of the composite emulsion was characterized by transmission electron microscopy（TEM）.The chemical structure,surface chemical element composition and thermal stability of the latex film were characterized by Fourier infrared spectrometer（FT-IR）,X-ray photoelectron spectroscopy（XPS）and thermogravimetric analyzer（TGA）.Finally,two liquid methods were used to calculate the surface energy of the latex film.The results show that the conversion rate of emulsion monomer is 89-92%,and the stability is good.Micellar particles have obvious core-shell structure and the particle size is 220±10 nm.The monomers all participated in copolymerization.The content of fluorine in the film-air interface is 15.8%higher than that in the film-glass interface,and fluorine atoms tend to enrich in the film-air interface.The thermal stability of latex film was improved by introducing nano-Si O₂.The surface energy of the composite latex film is 12.11 m N?m^-1.（3）Comparison and effect evaluation of amphiphobic processes of cellulose fabricsThe composite emulsion was finished on the cotton fabric by padding and spraying methods respectively.The surface morphology and wettability of the cotton fabric before and after padding were compared by scanning electron microscopy（SEM）,water immersion grade test,hydrostatic pressure test and water and oil contact angle test.The amphiphobic properties,antifouling and self-cleaning properties,durability and wearability of the fabric treated by padding were discussed.The results show that the hydrophobic effect of spraying method is similar to that of padding method,but the fabric finished by padding method has better oleophobic property.The contact angle of water and oil can reach the highest of 145.7°and 121.6°for the fabric finished by padding method,and the contact angle of water and oil remains unchanged within 60 s.In addition,the water grade and hydrostatic pressure of the fabric finished by the padding method can reach 4（90 points）,and the hydrostatic pressure can reach 2.69 k Pa.It has a certain anti-fouling and self-cleaning ability,and it can withstand 25 laundering cycles and 800 abrasion cycles,so it has good amphiphobic characteristics.