Preparation Of Flourinated Polyacrylate And Polyurethane Composite Emulsion By Microemulsion Polymerization And Its Self-organized Gradient Distribution Behavior

Waterborne polyurethane(WPU)which has hydrophilic structure shows the excellent properites of adhesion and elasticity.But lacked of chemical crosslinking and solvent resistance are not ideal.Fluorinated acrylate polymers have a wide range of applications due to their excellent surface properties,weatherability and environmental friendness,but their appliciationgs are limited because of high cost and difficulty in binding to most substrates.The introduction of fluorine-containing groups into the WPU structure not only retain the excellent mechanical properties and the two-phase microstructure characteristics of the WPU,but also greatly improve the surface properties and the overall performance of the WPU.It has become an emerging development direction of the WPU.Blending polymer gradient material is a mixture of different polymer components through physical methods.The particle size or composition of the dispersed phase in the blend system present a gradient structure,which has become a hot spot in recent years and the self-assembled polymer gradient materials are striking.The emulsions was synthesized by microemulsion polymerization.Isophorone diisocyanate(IPDI),polyether glycol(PTMG),N-methyldiethanolamine(MDEA),trimethylolpropane(TMP)and perfluoroalkyl acrylate(FA)were used to prepare fluorinated polyurethane(PUFPA)emulsions at different amounts of FA.The effects of formulation components,process conditions and dosage of FAon the polymerizability of PUFPA blend emulsion and the relationship between the microstructure and properties of the composite emulsion and its latex films were studied.The PUFPA emulsions with different amounts of FA were deposited on PTFE at 45?.The influence of the amount of FA on the distribution behavior of self-organized gradient structure and the surface properties of the latex films were analyzed.Moreover,the influences of the different base material,film-forming temperature of FA and heat treatment on the self-assembled gradient structure and surface properties of the blended latex films were discussed.The results showed:(1)The average particle size of WPU emulsion was 56.38 nm.With the increased of the amount of FA,the stability of the emulsion decreased.The viscosity decreases with the increased of FA content and the surface tension of PUFPA emulsion decreased obviously.The shape of the most gel particles was ellipsoid,and the size was basically uniform.The highest tensile strength,which was11.97 MPa,when the amount of FA was 40 %,increased by 292 %compared with WPU latex film;(2)With the increase of FA content,the difference of surface energy between film F-A(film-air)and film F-P(film-polytetrafluoroethylene substrate)was not obvious when FA content was below 30 %,the phase stratification of film sections were fuzzy,and the fluorine concentration was evenly distributed in the film thickness direction.When the amount of FA was 30 %,the difference of surface energy between film F-A and film F-P began to increase,the phase of film was delaminated.The film closed to the surface of F-A was flat,while close to the surface of F-P was rough.When the amount of FA was 40 %,the difference of surface energy between film F-A and film F-P was the largest,and the phase stratification of film sections were obvious.The concentration of fluorine element near F-A surface was higher than that of F-P surface,the fluorine concentration in the thickness direction of the film basically showed a gradient change.The PUFPA40% latex film showed a gradient structure;(3)When the film forming temperature on the base material of PTFE and Glass was higherthan 45?,phase separation occurs in the cross section of the film.The concentration of fluorine in F-A(film-air)began to be higher than the F-P/G(film-substrate)surface.The fluorine-containing component was enriched in the F-A surface.Fluorine element concentration decreased gradually from the F-A surface to F-P/G surface.The content of F element in the F-G surface was 35.59 % when the film forming temperature was 60? and the base material was Glass.When the films were heat-treated,the content of F element in the F-G surface was19.72 % and 15.87 % lower than that at 60?,The fluorine component was enriched on the F-A surface,and the gradient structure was more obvious.The content of fluorine in F-A surface(40.35 %)was significantly higher than that of fluorine in F-G(20.39 %),and the structure gradient was more obvious after heat treatment(110 ? /2h).The content of F element in F-P began to show a gradual difference when the the film forming temperature were exceed 45?and the base material was PTFE.When the film forming temperature was 60?,the content of F element on the F-P surface was 24.86 %.After the latex film was heat-treated,the content of F element on the F-P surface was20.39 %.For 110?/2h heat treatment,the gradient structure resulted in distinctly different free energy on both sides of the film.The contact angles of the F-A surface after the PTFE and glass films are formed132.5° and 137.7°,respectively.And the film reached the level of superhydrophobicity and formed gradient structure in the direction across the film thickness.