Preparation And Study Of Properties Of Anticorrosive Waterborne Polyurethane Coatings For Container

A kind of anticorrosive water-borne polyurethane exterior surface coating forcontainer with both good anticorrosion performance and excellent workability isprepared, and different influencing factors of the anticorrosion performance andworkability of the coatings are discussed in detail in this paper. The paper consists oftwo parts.In the first part, the anticorrosive properties are studied by use of electrochemicalimpedance spectroscopy (EIS),Observation with Scanning Electron Microscope(SEM),salt spray test and conventional immersing experiments. Effectes of type ofwaterborne polyurethane dispersion and type of Acrylate Emulsion as film formingmaterial, ratio of film forming material, type of anti-rust pigments, pigment volumeconcentration (PVC)on the anticorrosive properties were discussed in detail. Theresults show that:the film reach the best balance between mechanical property andanticorrosion performance when One-Component waterborne polyurethane dispersionA with good mechanical property and styrene-acrylic emulsion E with excellentanticorrosion performance are chosen as main film forming material and the massratio of film forming material A to E is8:2; the optimal anti-rust pigment is zincphosphateate and the anticorrosive properties of coatings are excellent when it isapproximately17percent of the total amount of pigments; the optimal PVC is25%and the film of coatings is the densest;experiments have proved that the results ofEIS&SEM and soaking experiment&salt spray test are basically the same.In the second part, effectes of pinhole, shrinkage, sagging on the film of coatingswere discussed in detail by using simulation of construction and evalution onworkability. The early water resistance of coatings, film formability at lowtemperature,anti flash rust,winter resistance,storage stability have been improved byreasonably designing formulation of paint. The results show that:right type anddoesage of defoaming agent,film-forming agent can help reduce or even eliminatepinhole in the film surface when airless spraying;Shrinkage is related to preparation process,substrate wetting agent/leveling and viscosity. Wet film thickness of maximumresistance to sagging is up to270μ m when high thixotropy acrylic thickener is used; The earlywater resistance of coatings increase significantly by using hydrophobe SR17;whenthe usage of film-forming agent M2/M3with good plasticity is more than3percentsby weight,the film of coatings can form normally at0～5°C; Raybo60with0.3%byweight is able to prevent flash rust; The freeze-thaw stability of coating is good withadding propylene glycol3%by weight; the storage stability of the coating withpolycarboxylic acid sodium salt dispersant is the best.All the properties of the anticorrosion performance and workability ofwater-borne polyurethane exterior surface coating for container prepared in this paperbasically reach the demands for solvent-based coatings for container in thestandardes of JH/T E01-2008. The anticorrosive water-borne polyurethane exteriorsurface coating for container will have a broad future for application.