Synthesis Of Fluorine-containing Finishing Agents And Their Applications On Surface Modification

It has been known that fluorocarbons have an extremely low surface free energy and they are widely applied for water and oil repellent finishing.Along with the improvement of people's living standard,fluorine-containing finishing agents with excellent water and oil repellency and(or)new function are demanding.The employment of other modification technique to improve water and oil repellency and development of fluorine-containing finishing agents with new functions are needed to meet the above demand.In this study,several kinds of fluorine-containing finishing agents were synthesized,applied on cotton fabric,glass and crystal silica substrates directly or combining other surface modification technique.The properties of the treated substrates were studied.The main work is described as follows.1.At present,the method for the fabrication of superhydrophobic surface has already become the research hot spot.In this study,sol-gel technique was employed and combined with fluorine-containing finishing agents to fabricate superhydrophobic cotton fabric coating.By changing the concentration of NH₃·H₂O catalyst,a series of silica sol samples(sol 1-5)with different silica nanoparticle sizes between 100 and 200nm were prepared successfully.Perfluorooctylated quaternary ammonium silane coupling agents PFSC was synthesized and applied on cotton fabrics with silica sol samples.The hydrophobic and oleophobic properties were determined in terms of H₂O and CH₂I₂ contact angle measurements and water and oil repellency rating measurements.As a result,silica sol sample sol 4 with appropriate size of silica nanoparticles was effective for increasing surface roughness,and the cotton fabric treated with it and PFSC showed better water and oil repellency than with PFSC alone. The H₂O contact angles increased from 133°to 145°,which was nearly superhydrophobic;and the CH₂I₂ contact angle increased from 125°to 131°.The water and oil repellency ratings increased from class 3 to 4 and class 4 to 5 respectively.The cotton fabric treated with other four silica sol samples and PFSC showed no increase in water and oil repellency.2.Usually the dirt particles do not adhere to low-energy surfaces of fluorinated polymers.However,once it was dirty,it is difficult to clean with water due to its good water repellent property.In light of this limitation,the smart surface exhibiting oleophobic/hydrophobic to hydrophilic switching property was demanded for minimizing adhesion in air and facilitating soil release in water.In this study, poly(perfluoroalkylated acrylate-acrylic acid)(PPFAA-AA)copolymers were prepared by the emulsion copolymerization of perfluoroalkylated acrylate and acrylic acid and applied on cotton fabric by pad-dry-cure process,the PPFAA-AA coating thus obtained exhibited oleophobic/hydrophobic to hydrophilic switching property, With the constant concentration of emulsifying agents,PPFAA-AA samples (eopolyl-4)were synthesized by changing the weight ratios of the two monomers, The copoly2 showed the best hydrophobic to hydrophilic switching property among these samples,and the water contact angles decreased from 127°to 33°within 30min. The hydrophobic to hydrophilie switching mechanism was proposed and verified by XPS measurements of chemical composition changes at different depth of the dry and wet PPFAA-AA coatings on cotton fabrics respectively.3.In the daily life,the fog on the transparent substrate and the static on the textile embarrassed people.One solution is to modify the surface with hydrophilic finishing agents.In this study,the polymer Rf-(DMDAAC)n-Rf with hydrophilic and oleophobic properties was designed,the hydrophilicity was used for antifogging and antistatic;the oleophobicity was used for antisticking,so the washing times can be reduced and the finishing effect was prolonged.First,the perfluoropolyether diacyl peroxide((RfCOO)₂)was synthesized and then used for initiating the polymerization of dimethyldiallyl ammonium chloride(DMDAAC)to give the perfluoroalkoxyl end-capped polymer Rf-(DMDAAC)n-Rf.The polymer was applied on cotton fabric by pad-dry-cure process.The treated cotton fabric showed hydrophilic and oleophobic, the water and hexadecane contact angles on the surface were 0°and 117.5°respectively.4.Self-assembly technique is widely used in surface modification.At the end of this study,perfluoroalkyl-containing compound was introduced to the surface of the glass and single crystal silicon substrates by self-assembly technique to lower the surface free energy and prepare ultra-thin water and oil repellent films.Self-assembled dual layer films PFOA-APTES on single crystal silicon and PFOA-TESPA on glass substrate were prepared respectively.The structure and morphology of the dual layer film PFOA-APTES were characterized by means of atomic force microscopy(AFM), ellipsometry and X-ray photoelectron spectroscopy(XPS)and the results demonstrated that the dual layer film was prepared successfully.The water and oil repellency of PFOA-APTES were measured in terms of contact angle measurements. The dual layer film PFOA-APTES obtained by reaction of PFOA with APTES-SAF for 12h showed better water and oil repellency than others.About self-assembled dual layer film PFOA-TESPA,the preparation conditions of TESPA-SAF and PFOA-TESPA were mainly studied.But the water and oil repellency measurements indicated that the preparation was not very successful.