Preparation And Properties Of Cationic Waterborne Polyurethane Emulsion Modified By Fluorosilicone

The water resistance of waterborne polyurethane film is reduced due to its hydrophilic groups,which limits the application of polyurethane materials.In this paper,waterborne polyurethane was modified by fluorine and silicon compounds to improve its water resistance so as to expand the application field of polyurethanes.Firstly,the cationic waterborne polyurethane emulsion was synthesized by selfemulsifying method using 3-dimethylamino-1,2-propanediol(DMAPO)as the cationic hydrophilic chain extender.Then,a series of waterborne polyurethane/fluorinated acrylate(WFPUA)emulsions were prepared by free radical emulsion polymerization using polyurethane emulsion as seed emulsion,methyl methacrylate(MMA)and hexafluorobutyl acrylate(F6BA)as modifiers.The effects of MMA and F6 BA content on the properties of hybrid emulsions and polymer films were investigated.In addition,cationic polyurethane has unique antistatic and bactericidal effects because of its quaternary ammonium group in the molecular chain.In order to prevent the undesirable accumulation of microorganisms on the substrate surface,improve the hydrophobic property of the coating and endow it with antibacterial effect,the effect of DMAPO content on the stability and antibacterial properties of the hybrid emulsion was checked and the properties of polymer films such as thermal stability,mechanical property and water resistance were discussed.The results show that when the R value is 1.6,n(PTMG): n(DMAPO)=1:0.65,the mass percentages of MMA and F6 BA are 25% and 20%,respectively,the WFPUA hybrid emulsion has good stability,and the film has the best hydrophobicity and excellent antimicrobial activity.The introduction of fluoroacrylate monomers into polyurethane molecular chains by grafting can improve the hydrophobicity of polyurethane film,however,the migration of fluorocarbon chains to the surface of the film is limited to some extent.The hydrophobicity of fluorinated polyurethane can not be greatly improved unless excessive fluorinated monomers are added,but the excessive fluorinated monomer will increase the cost of the product as well as affect the stability of the emulsion,resulting in the decline of the comprehensive properties of the film.Therefore,in order to further improve the hydrophobicity of waterborne polyurethane,polyurethane containing silicon(WSPU)emulsion was synthesized by using hydroxypropyl poly(dimethylsiloxane)(PDMS)as modifier monomer.And then,the fluorosilicone modified polyurethane(WSFPU)hybrid emulsion was successfully prepared by adding F6 BA monomer.The effect of the PDMS content on the properties of WSPU and WSFPU emulsion and film was studied.The results show that the average particle sizes of WSPU and WSFPU emulsion increase gradually and the stability becomes worse with increasing PDMS dosage,but the hydrophobicity of the film can be significantly enhanced.While maintaining the stability of the emulsion,the water contact angle and water absorption of the WSFPU film can reach 121.87° and 2.42%,respectively.