The Synthesis And Property Of Crosslinking Cured Polyurethane Cathodic Electrophoresis Resin

Polyurethane cathodic electrophoretic paint with aliphatic isocyanate as hard chain segment possess the low VOC content,non-flammable,anti-yellowing and good resistance to chemical.Based on the stronger adhesion,resistance to chemical corrosion and solvent of cross-linking cured waterborne polyurethane electrophoretic paint.In this paper,the synthesis and property of single-component and two-component waterborne polyurethane electrophoretic coating were studied,this thesis includs the following two parts.First,cross-linking cured single-component waterborne polyurethane electrophoretic coating was studied.We discussed some problems as following.The effects of electrophoretic conditions such as electrophoresis voltage,emulsion temperature and solid content on the appearance of paint film were researched.The effects of the different solvents and aid solvents on the performance of paint film were researched.The effects of soft chain segment,di-isocyanate,sealing side agent,PPG-EA,BPO,roast temperature on the appearance and property of paint film were researched.The results showed that the thickness and acid resistance of film could be improved with increasing electrophoresis voltage.Smooth and density film could be obtained at 30?for emulsion temperature,13%for solid content,1,4-Dioxane as main solvents,5%PPH as co-solvent.With molecular weight becoming smaller,the swelling rate of paint film with the same type of polyols was lower,water resistance was better,water resistance of polyether was better than polyester.When Wt(MDI)=100%,water resistance of the film reached to 480h and acid resistance reached to 18h.When Wt(HEMA)=5%?water resistance of the film reached to 528h and acid resistance reached to 16h.When Wt(PPG-EA)=3.08%,Wt(BPO)=0.6%and at 140? for baking temperature,acid resistance of the film reached to 18h and fog-corrosion reached to 984h.Second,cross-linking cured two-component waterborne polyurethane electrophoretic coating was studied.Water extender chain reaction process of curing agent was detected by NMR.The de-block process of cross-linking agent and the curing cross-linking process of two-component polyurethane resin were detected by in-situ FTIR.The thermal performance of film were analysed by TG and DSC.The morphological structure of film were analysed by XRD.The effects of roast temperature,roast time and emulsion solid content on the appearance and performance of paint film were researched.The effect of soft chain segment on the property of paint film was researched.The effects of catalyst,co-solvents on the appearance and performance of paint film were researched.The results showed that the proper MDEA extension reaction time was 60 min.When the temperature was over 70 ?,the bands sites,such as-NH and-C=O groups associated with hydrogen bond interaction,shifted to the higher wave-numbers,and the-NCO groups were de-blocked and to participate in cross-linking reaction at or above 120 ?.The de-block process and the curing cross-linking process of two-component polyurethane resin were detected by in-situ FTIR.The change of the temperature mainly influenced the absorption intensity of-NH and-NCO groups.The catalyst DBTDL helped improve film thermal stability.The internal structure of polyurethane became neater at 5.0 for R.Under the condition of 140?*1h,solid content at 15%,curing agent content at 15%and PTMG-1000 as soft segment,the film was smooth and density,acid resistance reached to 24h.Acid resistance of film could be effectively enhanced by DABCO.The de-blocked temperature of curing agents could be reduced and the sagging phenomenon of paint film could be improved by DBTDL.The surface tension of emulsion could be reduced by isopropanol and the film defects such as pinhole and bubble could be improved.