Preparation And Anticorrosive Property Of Polyurethane/Water Glass Composite Coatings

Waterborne organic anticorrosive coatings are most widely applied but difficult to meet the corresponding requirements in special corrosive environments like high-temperature corrosive environment.Waterborne inorganic silicate coatings are just appropriate but still have some problems such as strong hardness,poor flexibility and water resistance,which affect anticorrosive properties.Polyurethane has excellent flexibility and water resistance.Therefore,this paper took potassium water glass?PWG?as the research object and used polyurethane elastomer and zinc powders to modify PWG.Polyurethane/water glass composite coatings were prepared and their related properties were studied.The detailed research contents and results are as follows:?1?The extraction process of active silanol in potassium water glass is explored.It analyzed four factors on the system stability and the effective concentration of active silanol solution concluding the diluent concentration of PWG,pH value after acidating,the quantities of extraction agent?THF?and extraction time by single factor and orthogonal test methods.The optimum extraction process was acquired that the mass ratio of PWG:H₂O=1:9,pH=2 after acidating,the mass ratio of PWG:THF=1:10and the extraction time was 2.5h.?2?Polyurethane aqueous dispersions based on active silanol?Si-WPU?were synthesized by using isophorone diisocyanate?IPDI?,polypropylene glycol 1000?PPG-1000?and 2,2-dimethylolpropionic acid?DMPA?as raw materials and active silanol as internal crosslinking agent.The properties of Si-WPU and its film were investigated by analyzing four factors concluding the isocyanate index?R?,the content of DMPA,soft segment and active silanol.The optimum synthesis process was that R=1.2,the contents of DMPA were 5%of prepolymer,the contents of soft segment were40%and the additive amouts of active silanol were 70%of prepolymer by analyzing dynamic potential polarization curves and electrochemical impedance spectroscopies.?3?The blending systems of Si-WPU/water glass were prepared.The optimum additive amounts of Si-WPU were 7%by researching effects of Si-WPU on properties of the blends.With water resistance time as the evaluation standard,the best curing conditions were obtained:the curing temperature was 60°C and the curing time was 4h.The addition of Si-WPU improved water resistance and flexibility of the coatings,but the heat resistance was reduced.?4?With zinc powders as curing agents and Si-WPU/water glass blending system as the main materials of forming film,Si-WPU/water glass composite coatings were prepared.The best additive amounts of zinc powders were 50%mass of Si-WPU/water glass blends and the best additive amounts of flake zinc powders were 35%mass of total zinc powders.Comparing with the pure potassium water glass coatings and the marketed inorganic zinc silicate coatings,the prepared composite coatings had excellent mechanical property and water resistance.The problems of poor water resistance and flexibility of the waterborne inorganic silicate coatings have been solved.