Synthesis Of Water-Borne Auto-Oxidizable Polyurethane Based On Alkyd As Polyol And Its Anti-Corrosion Properties

Every year,metal corrosion causes a lot of economic losses,so it is necessary to treat the metal surface.One of the most effective and convenient ways to prevent metal corrosion is to coat metal surfaces with inorganic or organic coatings.Water-borne polyurethane can be formulated with water,fillers,and additives to form water-borne polyurethane anti-corrosion coatings for bridges and automobiles.Polyol is an important raw material for the preparation of water-borne polyurethane,which mainly comes from petroleum.However,with the increasing shortage of petroleum resources,it has become extremely important to find green and renewable polyol resources for the preparation of polyurethane.Therefore,in this study,bio-based alkyd was used as a polyol for the preparation of water-borne auto-oxidizable polyurethanes.The effects of the type of chain extender,fatty acid content,and aniline trimer content on the properties of water-borne autoxidation polyurethanes and coatings were investigated.The details are as follows:（1）Firstly,hydroxyl-rich alkyd resins were prepared from bio-based linoleic acid as raw material,and water-borne auto-oxidizable polyurethanes containing different chain extenders were synthesized with polyether polyol N210 as polyol and 4,4’-dicyclohexylmethane diisocyanate,2,2-bis（hydroxymethyl）propionic acid,and ethylenediamine,isophorone diamine,and diethylenetriamine as amine chain extenders.The experimental results showed that when isophorone diamine was used as the chain extender,its dispersion particle size was the smallest,and among the cured films of water-borne auto-oxidizable polyurethane prepared by the three amine chain extenders,the water absorption of the cured film was the lowest when the chain extender was isophorone diamine,which was only 7.52%.The corresponding film hardness was up to 2H and water resistance was up to 7 days.（2）In order to improve the fatty acid content,three different oil-length alkyd resins were prepared,while five water-borne auto-oxidizable polyurethanes with different fatty acid contents（25.02%,30.51%,35.36%,38.39%and 41.41%of fatty acid content,respectively）were prepared by controlling the type and amount of alkyd.The results showed that when the fatty acid content was 41.41%,the static viscosity of its dispersion resin was only 0.043 Pa·s;the crosslink density of its cured film was the largest among the five groups of samples,up to 1.16×10³ mol·m^-3;and the pencil hardness of its coating was H and the anti-anti-impact resistance was 50 cm.（3）In order to further improve the anti-corrosion performance of water-borne auto-oxidizable polyurethane,an aniline trimer with redox properties was selected as a chain extender to participate in the reaction.The results showed that when the content of aniline trimer was 5%（the amount of the total amine chain extender）,the corrosion resistance was greatly improved,and the corrosion rate was reduced from 12.9μm·Y^-1to 1.9μm·Y^-1 compared with that of the water-borne auto-oxidizable polyurethane without aniline trimer,but the viscosity did not change significantly.Therefore,the water-borne auto-oxidizable polyurethane based on alkyd as polyol prepared in this paper meets the requirements for the use of one-component water-borne polyurethane,and the introduction of aniline trimer can further improve the anti-corrosion performance of water-borne polyurethane.