Study On Preparation And Properties Of Antibacterial Waterborne Polyurethane

Waterborne polyurethane（WPU）,which has low organic volatile emissions（VOCs）,is gradually replacing the conventional solvent-based polyurethane as environmental protection and safety become more and more important.However,WPU can be easily invaded by bacteria or microorganisms,which causes cross-infection by forming biofilm,not only shortening the service life of the material but also harming human health during the application process.At present,antibacterial WPU is prepared by adding antibacterial agents such as small molecule antibacterial agent,metal particles（Ag,Cu）or nanoparticles（Zn O,Ti O₂）,which has the problems of thermal instability,and environmental pollution caused by antibacterial agents migration.To solve the above problems,three kinds of non migratory WPU materials with excellent antibacterial properties were prepared.The main research contents are as follows:（1）Quaternary ammonium salt antibacterial waterborne polyurethane was prepared by introducing amine compounds.Polyurethane prepolymer containing tertiary amine was synthesized by compounding polycarbonate diol（PCDL）and polyethylene glycol（PEG）as soft segment,isophorone diisocyanate（IPDI）as hard segment,3-dimethylamino-1,2-propanediol（DMAPD）as chain extender and 2-hydroxyethyl methacrylate（HEMA）as capping agent.Alkanes with different chain lengths were introduced for quaternization reaction,and quaternary ammonium salts WPU were prepared by UV curing.The results showed that the tertiary amine group in WPU molecular chain was successfully quaternized.When the dosage of DMAPD was 9 wt%and the number of alkyl long chains of quaternary ammonium salt was10,the degree of quaternization of the material was higher,and the Q value indicating the reaction degree was 0.187.The surface of WPU film was hydrophilic,and the antibacterial rates of WPU-9-10 and WPU-9-12 to E.coli and S.aureus were all above 95%,with no bacteriostatic circle.The tensile strength of WPU film increased with the increasing of DMAPD content,and the longer the introduced quaternary ammonium alkyl chain,the better the toughen effect.However,the introduction of quaternary ammonium salt decreased the thermal stability of WPU,as the thermogravimetric temperature decreasing to 247.5℃when the mass loss was 5%.（2）In order to improve and enhance the thermal stability and antibacterial property of WPU film,quaternary phosphonium salt WPU was prepared.Firstly,the quaternary phosphonium salt antibacterial monomer（QPS）was successfully synthesized and its chemical structure and minimum inhibitory concentration were determined.Then,the QPS was introduced into hexamethylene diisocyanate trimer,which together with IPDI as the hard segment,PCDL as the soft segment,and DMAPD and BDO as the chain extender to prepare the quaternary phosphonium salt WPU.The structure of QPS was analyzed by FT-IR and NMR,and the effect of QPS content on the properties of quaternary phosphonium salt WPU was discussed.The results showed that as a hydrophilic monomer,QPS could reduce the particle size of WPU dispersion and increase the surface potential.When the content of QPS reached 3wt%,the antibacterial rates of the quaternary phosphonium salt WPU film against E.coli and S.aureus were above 98%and the antibacterial circles of its dispersion could reach 12.96 mm and 13.09 mm,respectively,indicating that the antibacterial property of the quaternary phosphonium salt WPU was better than that of the quaternary ammonium salt WPU.In addition,the quaternary phosphonium salt WPU had good thermal stability.The interaction of the WPU molecular chain’s hydrogen bonds,however,was dramatically diminished with an increase in QPS concentration,which led to a decline in the material’s mechanical characteristics.（3）For further improving the antibacterial and mechanical properties of WPU,the antibacterial WPU/modified graphene oxide composites were prepared.The quaternary phosphonium salt monomer（TPP-OS）with siloxy groups was successfully synthesized by the allyl-triphenylphosphonium bromide and（3-mercaptopropyl）trimethoxysilane allyl-mercapto click addition reaction.Condensation reaction was employed to modify the GO,and then the modified GO was combined with waterborne polyurethane to prepare composite films.The chemical structure of TPP-OS was confirmed by FT-IR and NMR.The strength ratio of I_D to I_Gin the XRD of TPP-GO increased to 1.18,which indicates that the degree of defect increases,proving the successful preparation of modified GO.The antibacterial properties of GO material before and after modification were studied.It was found that the antibacterial property of GO material grafted with TPP-OS was significantly improved.Furthermore,the SEM characteristics demonstrated that using modified GO may boost the compatibility and interfacial effect between the particles and the matrix and prevent the aggregation of nanoparticles.When the content of TPP-GO was 0.5 wt%,the antibacterial activity of WPU/0.5TPP-GO film against E.coli and S.aureus reached more than 98%,indicating excellent antibacterial performance.And the maximum thermal weight loss temperature(T_max1)of WPU/0.5 TPP-GO composite film was about 20℃higher than that of pure WPU,the thermal stability performance was improved.Besides,the tensile strength of WPU/0.5 TPP-GO composite film reached 17.2 MPa,the elongation at break reached 625.1%,the mechanical properties were significantly improved.