Preparation And Anti-corrosion Properties Of Modified Waterborne Polyurethane

Waterborne polyurethane is a new generation of green environmental protection materials,which are widely used in coatings,synthetic leather,adhesives and other fields.In this paper,an aqueous polyurethane emulsion was prepared with isophorone diisocyanate(IPDI)and polytetrahydrofuranether glycol(PTMG)as the main monomers.The hydrophobic properties of waterborne polyurethanes are modified through the step-by-step design of the waterborne polyurethane synthesis process.At the same time,the application of waterborne polyurethane(WPU)emulsion in the field of anti-corrosion coatings has been deeply studied,and the content is as follows:1.Preparation of waterborne polyurethanes by different chain extension methods:1,4-butanediol(BDO)and N-[(2-amino)-amino]ethane sulfonated sodium(AAS)were used as pre/post-chain expanders,respectively,two different types of WPU emulsions were synthesized,and the effects of BDO and AAS addition on the performance of WPU emulsions and membranes were investigated.With the increase of BDO addition,the particle size of the waterborne polyurethane(WPU-Q)emulsion synthesized by the pre-expansion method decreased from 177 nm to 118 nm,and the tensile strength of the polyurethane film increased from 2.4 MPa to 24.2 MPa;with the increase of AAS,the particle size of the waterborne polyurethane(WPU-H)emulsion synthesized by the post-expansion method decreased from 216 nm to 137 nm,and the tensile strength of the polyurethane film decreased from 14.27 MPa increased to 31.59 MPa,water contact angle increased from 62°to 73°.2.Preparation of modified waterborne polyurethane:First,the polyurethane was hydrophobicly modified,and terminal hydroxy polydimethylsiloxane(Si-OH)was introduced into the system to explore its effect on the performance of WPU emulsion and membrane.With the increase of Si-OH content,the emulsion particle size of terminal hydroxy polydimethylsiloxane modified aqueous polyurethane(WPU-Si)increased from172 nm to 358 nm,the tensile strength of the polyurethane film increased from 7.2 MPa to61 MPa,the water contact angle increased from 75°to 83°,and the water absorption rate decreased to 9.5%.Secondly,on the basis of Si-OH modified WPU,the formula with the best performance of Si-OH is selected at a dosage of 6 wt%,and the ketohydrazine crosslinking reaction is introduced in this formula to form a crosslinking network.With the increase of DAAM content,the emulsion particle size of WPU-T decreased from 151 nm to117 nm,and the water contact angle of polyurethane film increased from 84°to 92°.3.Research on the anti-corrosion performance of waterborne polyurethane:Four kinds of waterborne polyurethane prepared by the experiment in the first two chapters are mixed with anti-rust filler to obtain four kinds of waterborne polyurethane coatings.The four coatings were coated on the iron sheet,and the test characterization of corrosion resistance related to hardness test,adhesion test,acid and alkali salt resistance test and electrochemical impedance test was carried out Through the test,the following conclusions were drawn:the four coatings have good hardness and corrosion resistance properties,the polyurethane coating(WPU-T)with ketone hydrazine crosslinking modification has the best corrosion resistance performance,and the electrochemical impedance mode value can reach 7×10~3Ω.