Preparation And Properties Of UV-Curing Waterborne Fluorinated Pure Acrylic Polyurethane Acrylate

In the past decade, UV-curable waterborne polyurethane acrylate resins have beenextensively studied for its unique combination of environmental-friendliness, lowerenergy consumption and excellent properties. Fluorinated polyurethane coating waswidely used in many areas because of the lower surface energy and excellent water andoil repellency resistance. The polyacrylate random copolymers with side chaincontaining hydroxyl, carboxyl and different fluorine terminal group were prepared, andwere further modified to prepare waterborne UV-curable fluorinated pure acrylicpolyurethane acrylate. The structure of resin, emulsification process, properties ofemulsion and coating were studied. And then the migration and surface enrichmentbehavior of fluorine terminal group during the film formation process were also studied.According to the change of film surface energy, the effect of structure and content offluorine terminal group on water resistance of film were discussed. The mainconclusions were as follows:A series of polyacrylate random copolymers, with different content side chains ofcarboxyl and hydroxyl, were synthesized via the solution polymerization of methylmethacrylate, butyl acrylate, hydroxyethyl methacrylate and acrylic acid. The resultedresins were further modified by isophorone diisocyanate and hydroxyethylmethacrylate to prepare UV-curable pure acrylic polyurethane acrylate. The structureof the products were characterized by Fourier transform infrared spectroscopy (FTIR),1Hnuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC). Theconversion of-NCO during the preparation of polyurethane was characterized. And thephysical properties of cured films were tested. The results showed that the expectedproduct was prepared successfully. The appropriate temperature of reaction PA withpolyurethane (PU) intermediate was45℃. And the physical properties of cured filmsare good.The waterborne UV-curable emulsion were prepared by neutralization and emulsion of pure acrylic polyurethane acrylate. The effect of AA content, shear rateand shear time on the size and stability of emulsion were studied. The results showedthat the emulsion viscosity increased as the content of AA increased, while the size ofemulsion decreased at first and then increased, and hydrophilic of cured filmsincreased with increasing AA content. The appropriate shear rate, shear time and AAcontent were2000r/min,20min and10～15%respectively.The polyacrylate random copolymers with hydroxy, carboxyl and differentfluorine terminal group side chain were prepared. The resulted polyacrylate was furthermodified to prepare waterborne UV-curable fluorinated pure acrylic polyurethaneacrylate emulsion. The structure of products were characterized by FTIR,1H NMR andDSC. The particle size and stability of emulsion were also studied. The surfaceenrichment behavior of fluorine terminal group and surface energy of films werestudied by X-ray photoelectron spectroscopy (XPS) and contact angle measurement.The results showed that the size of emulsion increased with the fluorinated groupaddition, while the stability of emulsion declined. Meanwhile, the surface enrichmentphenomenon of fluorine group was very obvious and the migration of fluorine terminalgroup could further improve after annealing. The surface energy of coatings decreasedsignificantly, and water contact angle increased significantly. Therefore, the waterresistance of coatings was improved, and the hydrophilic of cured films decreasedsignificantly. In addition, the stability of emulsion and surface properties of films weresuitable as the fluorine monomer content about6%.