Development Of Fluorine-free Water Repellent Based On Two-component Polyacrylate Copolymer Latex

Water-repellent finishing of fabrics refers to the use of water-repellent agents in post-processing to change the surface structure of the outer fibers of the fabric,forming a hydrophobic surface that prevents water from wetting the fabric and penetrating through it.Currently,most water-repellent agents are organic fluoropolymers with low surface energy,which have excellent water-repellent properties.However,with the discovery of their environmental and biological toxicity,there is an increasing demand to ban the use of such polymers,which has spurred the rapid development of environmentally friendly,fluorine-free water-repellent agents.There are three main types of fluorine-free water repellents: polyurethane,organosilicon,and polyacrylate.Compared to the first two types of water repellents,polyacrylate water repellents have the advantages of low raw material costs and simple production processes.However,their applicability to fabrics is limited,especially for loosely structured fabrics such as Oxford cloth and cotton,where the water repellency effect is poor.Cassie-Baxter simulation calculations have shown that waterproofing is the comprehensive result of the chemical composition of the water repellent and the surface physical morphology formed by its film formation.Inspired by this,this paper designs a high-film-forming PAs emulsion and a high-shape-retention PAh emulsion,and combines the two.The high film-forming property of PAs allows it to form a film covering the outer fibers,giving the surface a "chemical composition" of water repellency;the high shape-retention property of PAh allows it to form nano-sized "protrusions" and embed them in the water-repellent film formed by PAs,forming a lotus-leaf-like waterrepellent morphology,thereby enhancing the water repellency performance of the fabric.The study shows that:(1)In the emulsion polymerization of stearyl acrylate(SA),the addition of ethylhexyl acrylate(2-EHA),dodecanethiol(1-DDT),and isopropanol(IPA)can respectively decrease the glass transition temperature of the polymer,the polymer chain length,and the average particle size of the emulsion,and improve the film-forming performance of PAs emulsion.However,it was found through testing that when the content of 2-EHA in the copolymer composition exceeded 10%,the water repellency of the emulsion film rapidly decreased.Additionally,excessive amounts of IPA(>8.08%)and 1-DDT(>2%)no longer significantly improved the film-forming performance of the copolymer emulsion.Therefore,considering all factors,this paper adopts a copolymer composition of PAs emulsion with 10% 2-EHA by monomer weight,2% 1-DDT by monomer weight,and 8.08% IPA by water phase weight,and obtains a PAs emulsion with an average particle size of 120 nm and excellent film-forming ability;(2)In the emulsion polymerization of stearyl acrylate(SA),PAh latex particles with excellent shape retention ability were obtained through copolymerization with crosslinking monomers.During the process,four crosslinking monomers,namely 1,4-butanediol diacrylate(1,4-BDDMA),allyl methacrylate(AMA),γ-(2,3-epoxypropoxy)propytrimethoxysilane(KH560),and 3-Methacryloxypropyltrimethoxysilane(KH570),were investigated.The surface morphology of the latex film after copolymerization with the four crosslinking monomers was observed using atomic force microscopy,and combined with the analysis of the roughness of the latex film,it was found that KH570 was the most effective crosslinking monomer for improving the shape retention ability of the latex particles,with an optimal usage range of 12% to 15% of the monomer mass.Therefore,PAh-D and PAh-E latexes with particle sizes of 190 nm and 220 nm,respectively,were obtained by using KH570 at 12% and 15% of the monomer mass;(3)When PAh-D or PAh-E were separately paired with PAs to form two-component latex,the resulting products were used as water repellents to treat different densities of polyester fabrics such as chiffon,spun yarn,and Oxford cloth,as well as cotton fabrics.The water contact angles of the treated fabrics were all above 138°.Atomic force microscopy was used to examine the fabrics after treatment,and it was found that when the 190 nm particle size PAh-D emulsion was paired with PAs emulsion,it formed a "micro/nano" structured film with higher roughness on the surface of the fabric fibers compared to the 220 nm particle size PAh-E emulsion,resulting in better water repellent performance.;(4)After using the PAs/PAh dual-component polyacrylate fluorine-free water repellent agent for finishing,the water repellency of the fabric has good resistance to friction.After 50 friction cycles,the water repellency level of the finished fabric can still reach level 5,and the air permeability and moisture permeability are excellent.