Study On Preparation And Properties Of Two-Component Waterborne Polyurethane

Two-component waterborne polyurethane(2K-WPU)not only has the advantages of low film forming temperature,strong adhesion,good weatherability,but also meets the environmental protection requirements.However,the presence of hydrophilic groups in the molecular chain,result in poor water resistance of the film.In addition,the film’s heat resistance,chemical resistance,also need to be improved.In order to expand the scope of application of 2K-WPU,this paper starts from the point of molecular design,and appropriate to add modifier to modify the main chain to improve the comprehensive properties of 2K-WPU films,and applied to anti-corrosion coatings.(1)With isophorone diisocyanate(IPDI),poly(propylene glycol)(PPG),dimethylol propionic acid(DMPA),triethylamine(TEA)as main raw material,polyurethane polyol dispersion was prepared by prepolymer method,and then compounded with hydrophilic isocyanate curing agents to form film.The effects of Ri,DMPA dosage,three hydroxy methyl propane(TMP),RT and neutralization degree,n-NCO/n-OH and curing temperature on the properties of HPUA and 2K-WPU films were discussed.When Ri,DMPA,TMP,RT,neutralization degree,solid content,n-NCO/n-OH,curing temperature of films was respectively 1.6,6%,2%,0.8,100%,40%,1.2,50℃,the film comprehensive performance is better.(2)Silicone modified waterborne two-component polyurethane was prepared with dihydroxybutyl terminated polydimethylsiloxane(DHPDMS)as modifier.Through infrared spectrum and nuclear magnetic resonance spectroscopy test,DHPDMS was found to be successful in the polyurethane molecular chain.When the amount of DHPDMS was 5%,the viscosity of polyurethane was small,and the particle size was moderate,which could be stored for more than 6 months.The contact angle and water absorption of the modified film were respectively increased and decreased.The water absorption was reduced from 13.9%to 6.2%with the addition of 5%DHPDMS,and the contact angle increased from 60 to 95.TGA experiment showed that the heat resistance of the film was improved from 266.3℃ to 272℃when heat loss was 5%.XRD experiment showed that the crystallinity of the film was decreased with the increase of the organic silicon content.(3)The composite modified two-component waterborne polyurethane was prepared with epoxy resin,E-44 which was bisphenol A type and DHPDMS as 2K-WPU compound modifiers.The structure of polyol and its cured film were tested by infrared spectrum and nuclear magnetic spectrum.The results showed that E-44 and DHPDMS were all successfully connected with polyurethane molecular chain.When the dosage of DHPDMS was 5%and the dosage of E-44 was 4%～6%,the performance of the polyol was better.The heat loss data of the film showed that the heat resistance of the film was improved remarkably,and the temperature of the film was 287℃ when the weight loss was 5%.With the increase of the amount of E-44，the water absorption rate of the film decreased first and then increased,and the contact angle had been increasing.When the amount of E-44 was 6%,the water absorption rate was 4.4%,and the contact angle was 106°.The comprehensive properties of the compound modified films were better than that of the unmodified-film and polysiloxane-modified film.(4)Polyol component was prepared with silicone,epoxy resin modified polyurethane polyol dispersions as main film-forming substance,which mixed with coloring pigment titanium dioxide,anti-corrosion filler,and some coating additives.and polyol component mixed with curing agent component to form two-component polyurethane anticorrosive coatings.And The calculation of PVC and P/B showed a linear relationship between 1/PVC and 1/(P/B).Through single factor experiment method,the coating formulation was got the preliminary optimization,and got the optimum condition of the process and the main raw material usage.On this basis,this paper adopted orthogonal test to further optimize coating formulation.The results showed that when the dosage of Si/E-HPUA,the content of titanium dioxide,glass flake dosage,n-NCO/n-OH were respectively 65%,18%,15%,1.2,the acid,alkaline and salt resistant performance of anti corrosion coating could achieve the best.Hiding power,hardness,adhesion of the coating was respectively 86g/m2,2H,0 level.After separately immersed in acid solution for 22d,alkali solution for 20 days,salt water for 20 days,the coating surface had no obvious abnormality.Anti-corrosion performance was good.