Synthesis, Characterization And Application Of Fluoirne-containing Polyacrylate Soap-free Latexes

Owing to their low surface free energy, outstanding water-andoil-repellency and self-cleaning properties, high thermal and chemical resistance,etc., fluorine-containing polymers have been widely used in textile finishing,functional coatings, biomedical materials, and aerospace as well asmicroelectronics fields. Fluorinated acrylate copolymers possess both thefavorable adhesion property of acrylate resin and the inherent characteristics offluorine-containing polymers, such as high thermal, chemical, and agingresistance; low surface energy; excellent oil-and water-repellency. Hence, ithas attracted much concern. On basis of the reinforcement of the people’sresource and environmental awareness, how to synthesize fluorinated acryliccopolymers emulsion with anticipated macromolecular structure and propertiesin dispersed phase systems has proved to be a challenge in theoretical researchand products development. Common fluorinated polyacrylate emulsionprepared with traditional emulsion polymerization method contains lots of lowmolecule emulsifiers in physically adsorbed state, which have high mobility andan undesirable effect on the environment and the performance properties of thefilm like optics, electricity, surface property, hydrophobicity, and adhesion.Meanwhile, the relatively high market prices of the fluorinated monomers limittheir use, so researchers always hope to exploit possible polymerization strategyto minimize dose of the fluorinated monomers and simultaneously preserve theexcellent properties.Therefore, the soap-free emulsion polymerization method was utilized inthis context to design and synthesize three sorts of fluorine-containing acrylate copolymers soap-free latexes with novel molecular structure and particlemorphology. Some factors influencing the stability of emulsion polymerization,relevant properties of the latexes and their films were systematicallyinvestigated later. Then, the as-prepared latexes were applied in the textilefinishing, and also film morphology and chemical compositions on the cottonsurface as well as its performance properties were researched in depth. Themain research contents are listed as following:(1) Cationic fluorinated polyacrylate soap-free latexes (CFMBD) withcore-shell structure and blue fluorescence were synthesized by semi-continuousseeded emulsion polymerization of dodecafluoroheptyl methacrylate (DFMA)with methyl methacrylate (MMA), butyl acrylate (BA), anddimethylaminoethyl methacrylate (DM), maleic acid double ester-octadecylpoly(ethyleneoxy)20ether-ethylene trimethyl ammonium chloride (R303) as thecopolymerisable emulsifier and2,2′-azobis(2-methylpropionamidine)dihydro-Chloride (VA-50) as an initiator. Meanwhile, cationic fluorinated polyacrylatetraditional latex (GFMBD) was also fabricated as control with the sameprocedure and formulas except substituting R303for the1831/AEO-9mixedemulsifying system. Effects of the R303, VA-50and DFMA doses wereinvestigated on the stability of emulsion polymerization, the particle size andproperties of the latex film. The optimal condition for emulsion polymerizationwas that the R303and VA-50doses were3%and0.8%based on the totalmonomers weight, respectively, and the DFMA amount was8g in our recipe.Stable CFMBD latex with the average particle size of136.8nm could beobtained.Performance properties of the latex and its film were characterized bytransmission electron microscopy (TEM), scanning electron microscopy (SEM),thermogravimetry analysis (TGA), atomic force microscopy (AFM), X-rayphotoelectron spectroscopy (XPS), contact angle goniometer (CA), Fouriertransform infrared (FTIR) spectrometry, and nuclear magnetic resonancespectrum, etc. Results showed that the latex particles possessed the apparentcore-shell structure by TEM observation. Surface tensions of the CFMBDlatexes were among63.7-67.2mN/m and very close to that of water; whereassurface tension of the control fluorine-containing latex was36.9mN/m and almost equal to that of the mixed emulsifiers system (1831/AEO-9). Theaforesaid facts illustrate that R303copolymerizes with other monomers and isincorporated into the copolymer main chains, however,1830/AEO-9areadsorbed onto the latex particle surface and prone to separate from the body,finally it will freely disperse in water which should heavily lower the surfacetension of the system. Those latex films showed the increasing thermal stabilitybut the decline of surface tension and water absorption with augment of DFMAamount in polymer. When the DFMA dose was employed as10g, CA of wateron latex films could maximally attain108.5°and that of diiodomethane was91.5°while the surface free energy and water absorption were12.65mN/m and7.6%, respectively. XPS analysis indicated the fluoroalkyl groups had thetendency to enrich at the film-air interface, which plays a crucial role in thehydrophobicity and micro-morphology of the latex films. The fluorine-free latexfilm showed the relatively smooth surface morphology in its AFM image,however, there were numerous little protuberances on the film surface of theCFMBD latex from the polymer containing27.5wt%DFMA in total monomersweight dried at room temperature. Especially, after the annealing process, somepeaks and lots of protuberances on that film appeared and the surface roughnesswas greatly increased. Water contact angles (WCAs) of fluorine-free latex film,those of CFMBD film dried at room temperature and after the annealing processcould attain62.5°,102.5°and108.5°, respectively.Those would further confirmthat the fluoroalkyl groups tended to enrich at the film-air interface and theannealing process would be in favor of this tendency.Then CFMBD was utilized to treat the cotton fabric, and performanceproperties and surface morphology of the treated fabric were characterized byCA, whiteness meter, flexibility tester, AFM and FESEM. The treated cottonfabric by using the concentration of CFMBD as1.0g/100ml H2O had thefavorable water repellency. CFMBD didn’t influence whiteness of the treatedfabric but would make it slightly stiff at high doses. However, washingdurability of the treated fabric by CFMBD showed improvement compared tothe general emulsion resulting from the disadvantage effect of low molecularemulsifier on the film adhesion. CFMBD could form a smooth resin film on thetreated fabric/fiber surface under FESEM and AFM observations. (2) Self-crosslinking fluorinated polyacrylate soap-free latexes (FMBN)with core-shell structure and blue fluorescence were synthesized bysemi-continuous seeded emulsion polymerization of DFMA with MMA, BA,and N-methylolamide (NMA) as self-crosslinkable monomer, ammoniumallyloxtmethylate nonylphenol ethoxylates sulfate (DNS-86) as thecopolymerisable emulsifier and potassium persulphate (KPS) as an initiator.Impacts of the DNS-86, DFMA and NMA doses were investigated on thestability of emulsion polymerization, the particle size and properties of the latexfilm. The optimal condition for emulsion polymerization was that the DNS-86dose was3%based on the total monomers weight, the DFMA and NMAamounts were8g and1.5g in our recipe, respectively. Stable FMBN latex withthe average particle size of116.3nm could be acquired.Performance properties of the latex and its film were characterized byTEM, SEM, TGA, differential scanning calorimeter (DSC), AFM, XPS, CA,FTIR, and nuclear magnetic resonance spectrum, etc. Results indicated that thelatex particles possessed the uniform core-shell structure by TEM observation.The films formed from the FMBN latices thus had two Tg. Their thermalstability and Tgof the shell phase increased gradually with the augment of theDFMA amount in polymer. CAs of water and diiodomethane on latex films rosewith the increasing amount of DFMA. When the amount of the DFMA was10g,CA of water on latex film could maximally attain117.5°and that ofdiiodomethane was90.5°while the surface free energy and water absorptionwere11.47mN/m. XPS, AFM and hydrophobicity analyses indicated thefluoroalkyl groups had the tendency to enrich at the film-air interface. Thisenrichment of fluorine at the film-air interface was more evident after theannealing process. Meanwhile, hydrophobicity of the self-crosslinking soap-freelatex film showed some improvement compared to the general one and thenon-crosslinked one.Then FMBN was utilized to treat the cotton fabric, and performanceproperties and surface morphology of the treated fabric were characterized byCA, whiteness meter, flexibility tester, AFM and FESEM. The treated cottonfabric by using the concentration of FMBN as1.0g/100ml H2O had thefavorable water repellency. FMBN didn’t influence whiteness of the treated fabric but would make it slightly stiff. FMBN could form a smooth resin film onthe treated fabric/fiber surface under FESEM and AFM observations.(3) Polysilsesquioxane (PSQ) emulsions were firstly prepared by thehydrolysis and condensation reaction of methacryloxy propyl trimethoxyl silane(KH-50) in the aqueous phase, sodium hydroxide (NaOH) as catalyst andDNS-86as the emulsifier. Then fluorinated polyacrylate/PSQ hybrid soap-freelatexes (FPSQ) with core-shell structure and blue fluorescence were synthesizedby semi-continuous seeded emulsion polymerization of DFMA with MMA, BA,and PSQ as the seeded latex, DNS-86as the copolymerisable emulsifier andKPS as an initiator. Influences of the catalyst concentration, the DNS-86andKH-570doses were discussed on the particle size of the PSQ latexes. PSQemulsion with the average particle size of66.7nm could be acquired in100gaqueous solution while the concentration of the NaOH, the doses of the DNS-86and the KH-570were controlled as20mmol/L,0.3g and10g, respectively.Performance properties of the latex and its film were characterized byTEM, SEM, TGA, AFM, XPS, and FTIR, etc. Results demonstrated that thelatex particles possessed the core-shell structure by TEM observation. TheFPSQ film showed more excellent hydrophobicity than those of CFMBD andFMBN since the micro-roughness of the FPSQ had been enlarged due to theimported PSQ besides the role of the fluoroalkyl groups with low surface freeenergy. Their surface free energies decreased firstly and increased slightly withthe increasing amount of the imported PSQ amounts but showed a unilaterallydecreased trend with augment of the DFMA dose. Thermal stability of the FPSQfilms increased gradually with augment of PSQ amount in polymer. XPSanalysis indicated the fluoroalkyl groups had the tendency to enrich at thefilm-air interface. FTIR confirmed the structure of the as-prepared product.AFM results indicated that the hybrid latex film was coarser than the PSQ latexfilm.Then FPSQ was utilized to treat the cotton fabric, and performanceproperties and surface morphology of the treated fabric were characterized byCA, whiteness meter, flexibility tester, and FESEM. The treated cotton fabric byusing the concentration of FPSQ as1.0g/100ml H2O had more favorablehydrophobicity than those treated by CFMBD and FMBN. The treated fabrics became slightly whiter but its handle became worse. FPSQ could form a hybridfilm on the treated fabric/fiber surface under FESEM observation. There weresome nanospheres beneath the hybrid film.