Study On Synthesis And Properties Of Organic Fluorine Modified UV-curable Waterborne Polyurethane

C-F bond energy in fluorocarbon materials is very high,and fluorocarbon materials have low surface free energy.Fluorine can enrich in the surface of polymer and can shield and protect the polymer.So fluorocarbon materials have unique properties,such as superhydrophobic,low polarization,heat resistance and flame retardant,etc.But raw materials are expensive,production costs are very high.Waterborne polyurethane because of its excellent properties,such as chemical resistance,abrasion resistance and thermal stability,etc.,has been widely used in various fields,and waterborne polyurethane is a kind of green environmentally friendly coating.However,properties of polyurethane films can decline to some extent for introduction of hydrophilic groups.Study was carried out to modified polyurethane with fluoride monomers.And effects of fluoride monomers on the structure and surface properties of UV-cured films were investigated.First,UV-curable waterborne polyurethanes were synthesized by end-capped with hydroxyethyl methacrylate and synthesis conditions and process parameters were optimized.Effects of 2,2-bis(hydroxymethyl)propionic acid(DMPA)and the amount of photoinitiator on properties of emulsions and films were studied.The results showed that the optimum temperature of first step of polyurethane synthesis was 80℃,and dosage of dibutyl tindilaurate catalyst was 0.1 wt%.With increasing hydrophilic monomer DMPA,the particle size of emulsions decreased and stability can be improved.When amount of photoinitiator was 2.0 wt%,films were fully cured and were of excellent performance.Then,organic fluorine modified polyurethane systems have been studied.The main contents are as follows.Fluorine-containing polyurethane prepolymers were synthesized by end-capped using fluoride monomer.GMA were grafted into side chain of fluorinated polyurethane prepolymers and UV-curable waterborne fluorinated polyurethane prepolymers were finally prepared.The prepolymers were characterized via Fourier Transform Infrared Spectroscopy(FTIR).Properties of emulsions and surface of UV-cured films were characterized by laser particle size analyzer,thermal gravimetric analysis(TG),differential scanning calorimetry(DSC),water contact angle,and X-ray photoelectron spectroscopy(XPS)etc.The results showed that the optimum temperature of GMA grafting reaction was around 80℃.The particle size of emulsions increased with increasing fluorine content and emulsion stability decreased.Fluoride monomer can improve thermal stability of the polymer in a certain extent,and can improve the microphase separation of the hard segments and soft segments.The little fluoride monomer can significantly improve water contact angle.With increasing fluorine content,water contact angles of UV-cured fluorinated films increased and can reach 117°.Fluorine significantly enriched in the surface of films.And the water repellency were improved.Therefore,fluorine may reduce surface free energy and improve the water repellency of films.Fluorine-containing acrylate diols were synthesized with fluorinated acrylic monomer,MMA by solution polymerization,1-thioglycerol as the chain transfer agent,azobisisobutyronitrile as the initiator,tetrahydrofuran as solvent.UV-curable waterborne fluorinated polyurethanes were synthesized by incorporating fluorine-containing acrylate diol into polyurethane.The structure of fluorine-containing diol and fluorinated polyurethane acrylate were characterized via Fourier Transform Infrared Spectroscopy(FTIR)and nuclearmagnetic resonance spectrum(~1H-NMR).Molecular weight and its distribution were characterized via gel permeation chromatography(GPC).With increasing the reaction temperature of polymerization and the mass ratio of fluorinated acrylic monomer and MMA,the molecular weight distribution became wide.As the mole ratio of 1-thioglycerol and acrylic monomers increased,molecular weight decreased.The particle size of emulsions increased with increasing fluorine-containing diol.As the double bond content increased,the crosslinking density of films increased,and can improve heat resistance of films.Introduction of fluorine-containing diol can improve the surface water contact angle,and effectively reduce the surface free energy.