Synthesis And Application In Waterborne Coatings Of Composite Latex Based On Poly(Vinylidene Fluoride)

In this paper,we demonstrate a simple method for fabricating composite latex based on poly(vinylidene fluoride)(PVDF)with safe,environmentally friendly and low-cost characteristics,and its application in the field of waterborne coatings was investigated.First,the mixed acrylate monomers were added to the PVDF seed emulsion to swell it,and the poly(vinylidene fluoride)/polyacrylate(PVDF/PACL)composite latex with reactive groups was synthesized by seeded emulsion polymerization.By adjusting the feed ratio among different kinds of acrylate monomers,the as-prepared composite latex could easily form a film at room temperature with no baking.In addition,the chemical composition,morphology,phase transition behavior and self-assembly film-forming process of composite colloidal particles,as well as the surface composition,surface microstructure and comprehensive properties of latex coatings were systematically explored.The chemical composition,micromorphology,internal structure,self-assembly film formation process,size and size distribution,crystallization behavior,thermal stability,and glass transition temperature(T_g)of composite latex particles were characterized by fourier transform infrared spectrometer(FTIR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),environmental scanning electron microscopy(ESEM),dynamic light scattering(DLS),differential scanning calorimeter(DSC),thermal weight loss analyzer(TGA),dynamic mechanical analyzer(DMA),respectively.Moreover,the surface microstructure and surface composition of the composite coating were investigated by scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).The adhesion and organic solvent resistance of the coating were tested by the grid method and manual wiping method,respectively.The UV aging resistance of the coating was explored by ultraviolet aging tester and gloss meter.The results showed that:in this reaction system,the ratio of acrylate comonomers and the feed ratio of PVDF/mixed acrylate monomers were keys to the preparation of room-temperature curing waterborne coatings with excellent properties.SEM test results showed that the amount of butyl acrylate(BA)had a great effect on the morphology of PVDF/PACL composite particles.The DLS,DSC and TGA test results showed that the composite latex particles had a narrow particle size distribution,PVDF produced confined crystallization behavior and there was no longer a significant PVDF weight loss peak when the feed ratio of PVDF/acrylate monomers was 1:2 or less.These results showed that a uniform structure was formed with PVDF and PACL,and PVDF core particles could be completely encapsulated by PACL.Through DMA characterization,the T_g of composite particles with different methyl methacrylate(MMA)additions were obtained.The results showed that the PVDF/PACL composite latex could form a film at room temperatur when the MMA content was 35 wt%or less.The film formation process of composite latex particles was a dynamic drying process.A uniform coating with PVDF dispersed phase and PACL continuous phase was finally formed.The water-based composite coating showed good adhesion to the substrates and outstanding organic solvent resistance.Moreover,the coating almost retained the original gloss after tolerating high-intensity UV irradiations,indicating that the coating had excellent UV aging resistance.The above experimental results showed that the obtained PVDF/PACL composite latex had important application value in the field of waterborne coatings.