Synthesis And Properties Of Crosslinked Core-shell Fluorinated Cationic Waterborne Polyurethane Acrylate Emulsion

Waterborne polyurethane is one of the most important waterborne environment-friendly resins.Cationic waterborne polyurethane(CWPU)is especially suitable for surface treatment of leather,fabric and paper due to its positive charge.Traditional CWPU has a single structure and a hydrophilic group,so it is not good in water and solvent resistance.There are two ways to improve water resistance of CWPU:One is crosslinking modification;The other is that hydrophobic groups are introduced into the polymer.In this study,the fluorinated cationic water-based polyurethane acrylate(FPUA)with cross-linked core-shell structure was synthesized by modifying CWPU,with fluoroalkyl acrylate and internal crosslinking agent.Due to its excellent surface properties,FPUA materials are widely used in high-end architectural coatings,fabric finishing agents and leather finishing agents,etc.,with obvious industrial value.In this study,an internal crosslinked CWPU emulsion was prepared by using IPDI and PCDL as the main raw materials,n-methyl-diethanolamine(MDEA)as the hydrophilic chain extender,TMP as the internal crosslinking agent,and HEMA as the blocking agent.The effects of hard section content,MDEA dosage,TMP and HEMA dosage on the comprehensive properties of emulsion and rubber film were mainly discussed.A CWPU emulsion sealed with an ene bond as a seed,the monomer preemulsifier was prepared by mixing with vinyl monomers such as dodecafluoroheptyl methacrylate(DFMA),diacetone acrylamide(DAAM)and methyl methacrylate(MMA).The crosslinked FPUA composite emulsion with PU as shell and PA as core was prepared by core-shell emulsion polymerization.The effects of core-shell ratio PA/PU on the surface properties,mechanical properties and heat resistance of FPUA emulsion and film were mainly discussed.The emulsion and film were characterized by transmission electron microscopy(TEM),contact Angle measuring instrument,X-ray photoelectron spectroscopy(XPS)and atomic force microscopy(AFM).The results show that:when hard segment content is 45%,w(MDEA)=8%,w(TMP)=1.5%,n(HEMA/-NCO)=1:1,the storage stability of CWPU emulsion was not more than 6 months,the hardness was H,the adhesion level was 0,the impact resistance was50Kg/cm~2,and the tensile strength was 7.8MPa.In addition,when w(PA)=30%?50%,the stability of FPUA emulsion was the highest.When w(PA)=30%,the tensile strength was23.35MPa.When w(PA)=50%,the fluoride content on the film surface was 14.75%,the contact angle was up to 98.5~o,the water absorption rate was reduced by 80%,showing good hydrophobic performance.Under AFM observation,the surface flatness of the film is relatively high,and the size of the phase region fluctuates within 20nm.