Preparation And Performance Of Waterborne Polyurethane Anti-corrosion Coatings

Polyurethane is a structurally adjustable block copolymer linkage with urethane groups,containing soft and hard segments.The solvent of waterborne polyurethane(WPU)is water,which has the advantages of environmental-friendly.It has been successfully applied in coat-ings,leather finishing,biomaterials,elastomers and other fields.In this paper,room temper-ature curing waterborne polyurethane coatings were prepared by stepwise polymerization method,and waterborne anti-corrosion coatings with excellent anti-corrosion properties were prepared by increasing the network density of the system and the introduction of sub-sequent fillers.The specific studies are as follows:(1)First,the effect of different levels of vinyl-terminated WPU is discussed.WPU emul-sions with different end-closing rate were synthesized using hydroxyethyl methacrylate(HEMA)as capping agent,and the effect of HEMA addition on the performance of water-borne polyurethane emulsions and coatings was investigated.The results showed that with the increase of HEMA content,the particle size of WPU lotion increased from 77 nm to 117nm,and the mechanical properties decreased from 33.59 MPa to 1.61 MPa.When the end-closing rates was 70%,the comprehensive performance of the coating was the best,the static water contact angle can reach 89°,and the impedance modulus can reach 1.4×10~3Ω/cm~2.FT-IR analysis also showed that the target product was successfully synthesized.(2)Furthermore,to improve the network density of the coating,a room-temperature cur-ing system was introduced into the system.The effects of introducing diacetone acrylamide and dihydrazide on the waterborne polyurethane(WPU)emulsion and coating performance were investigated.The results showed that as the content of ketone hydrazine(TJ)increased,the emulsion particle size of WPU-TJ increased from 76 nm to 103 nm,and the tensile strength increased from 1.7 MPa to 6.8 MPa.When the ketone hydrazine addition was 4%,the static water contact angle of the coating reached 96°,and the impedance modulus reached3.1×10~3Ω/cm~2.The coating exhibited excellent corrosion resistance and the comprehensive performance of the coating wae the best.FT-IR analysis also confirmed the successful syn-thesis of the target product.(3)Finally,the two best-performing WPU coatings from the previous two chapters were compared with WPU coatings separately incorporating zinc powder(Zn)and graphene oxide(GO),as well as a WPU coating incorporating both fillers simultaneously.The five prepared coatings were separately applied to iron plates for electrochemical,pencil hardness,adhesion,and acid-base-salt resistance tests.The following conclusions were drawn from the tests:all five coatings performed well in pencil hardness and adhesion tests.The polyurethane coating modified with Zn/GO composite(WPU-Zn/GO)exhibited the best electrochemical and acid-base-salt resistance properties.The electrochemical impedance modulus reached 1×10~5Ω/cm~2,and it showed long-term anti-corrosion properties in a 9-day salt spray test.Its hard-ness reached 3H,and adhesion reached grade 0.