Study On Preparation And Properties Of Antibacterial Waterborne Polyurethane

Waterborne polyurethane（WPU）has gradually replaced polyurethane（PU）due to its environmental protection and simple production process,and its application involves printing ink,leather,biomedical and high-end new materials.However,WPU was prone to be attacked by bacteria during use,which could shorten its service life and caused the propagation of pathogenic bacteria and led to the spread of diseases.And this limited its applications in the field of high sanitary requirements.This paper mainly focused on the preparation of antibacterial WPU and its properties,exploring the combination of WPU material and antibacterial properties and its synthesis strategy,and studied the selection of antibacterial agents and the effects of the introduction of antibacterial agents on material properties.This paper studied the preparation of antibacterial WPU through four strategies.The specific contents are as follows:By grafting hydroxyethyl hexahydrotriazine（TNO）as antibacterial agent,TNO modified WPU（T-WPU）with different R values were prepared by regulating the molecular structure of chain segment.Then,the effects of different R values on the properties of T-WPU were investigated.With the increase of R value from 1.2 to 1.5,the initial decomposition temperature(T_5%)of T-WPU film was increased from 233.90℃to 256.40℃,and the antibacterial activity against Escherichia coli,Staphylococcus aureus remained above 80%,and the water absorption rates were below 11%after 8 h.The effect of changing R value on the glass transition temperature（Tg）of T-WPU was relatively small.But when R=1.5,the particle size distribution of T-WPU was wider than others,which occurred a small amount of sedimentation and the storage stability was slightly worse.T-WPU with R=1.4 showed the best comprehensive properties,the average particle size of the emulsion was 33.60 nm,the tensile stress of the film was 8.80 MPa,and the surface was hydrophobic,most importantly,the antibacterial activity reached 82.80%.Methods to improve the antibacterial activity of T-WPU film were explored,and chitosan（CS）was selected to prepare composite T-WPU.In order to enhance the compatibility between CS and T-WPU emulsion,CS was oxidized by hydrogen peroxide to obtain chitosan with low molecular weight（LCS）,and then chitosan composite WPU（CT-WPU）was synthesized by physical mixing LCS and T-WPU（R=1.4）.The structural changes of LCS were analyzed by X-ray diffrotometry and Fourier total reflection infrared spectroscopy,and the effects of LCS content on various properties of CT-WPU were explored.Besides,the cytocompatibility of CT-WPU was also investigated.The results showed that compared with T-WPU,the introduction of LCS increased the average particle size of CT-WPU composite emulsion,and the particle size distribution became wider.The surface of CT-WPU composite film was hydrophilic,and the antibacterial activity against Escherichia coli,Staphylococcus aureus reached more than90%,and the cytocompatibility was strengthened.When the content of LCS was 0.5%,the composite emulsion was stable and the comprehensive performance of CT-WPU film was the best,it not only had excellent antibacterial activity and cytocompatibility,but also the tensile stress of the composite film was enhanced to 13.30 MPa,decompositon temperature(T_10%)was increased to 289.53℃.However,the water absorption rate of the composite film had been reached 17.18%after 8 h,and the water resistance was poor.For improving the water resistance and antibacterial activity of T-WPU film,nano zinc oxide（Zn O NPs）were selected to prepare nano-composite antibacterial WPU.The surface of Zn O NPs were modified by 3-amino-propyl ethoxysilane（APTES）so as to improve the dispersity of Zn O NPs and reduce the aggregation of nanoparticles.After the organic hybridization,A-Zn O was prepared.And then it was used to prepare composite T-WPU（AT-WPU）through in-situ polymerization,the performance of AT-WPU was also investigated.The results showed that when the content of A-Zn O increased from 0.25%to 0.7%,the average particle size of AT-WPU composite emulsion was enlarged from 44.60 nm to 55.10 nm,the tensile stress of AT-WPU composite film was strengthened up to 11.20 MPa,the decomposition temperature T_10%was increased nearly 10℃.In addition,the antibacterial activity of AT-WPU against Escherichia coli,Staphylococcus aureus was above 90%.After 7 h,the water absorption rate was lower than 10%,the water resistance was enhanced.However,AT-WPU composite film had higher in-vitro cytotoxicity and poorer cytocompatibility than T-WPU.Especially,AT-WPU-0.7 composite emulsion had the aggregation of nanoparticles,which reduced its comprehensive performance.The antibacterial agents used for the three types of antibacterial WPU were relatively single,which was difficult to ensure the continuous and stable antibacterial activity of WPU materials.Phytic acid intercalated hydrotalcite（PA-LDH）was further studied to modify the three types of WPU,hoping to overcome the defects and obtain WPU composite functional materials with better comprehensive performance.First,PA-LDH was prepared by phytic acid（PA）with Aluminum nitrate nonahydrate（Al（NO₃）₃·9H₂O）,Magnesium nitrate hexahydrate（Mg（NO₃）₂·6H₂O）to improve the dispersion of LDH in WPU emulsion.LDH modified WPU（LDH/T-WPU,LDH/CT-WPU,LDH/AT-WPU）were obtained by mixing it with T-WPU（R=1.4）,CT-WPU-0.5 and AT-WPU-0.5.Then the properties of the three WPU composites were investigated.The results showed that the polydispersity index（PDI）of the three WPU composite emulsions were all close to 0.10,indicating that the emulsions had the characteristics of storage stability.The antibacterial activity of three WPU composite films against Escherichia coli,Staphylococcus aureus was nearly 100%.Compared with CT-WPU,the water absorption rate of LDH/CT-WPU decreased to about 15%after 8 h,which improved the water resistance.