| Polyurethane(PU) coating material is quite popular in the market for itsadvantages, such as the strong wear resistance, excellent adhesion, good anticorrosionperformance, fine thermal endurance and wide scope of construction. Polyurethanecoating material is mainly divided into two types that are solvent ones and waterborneones. Though solvent polyurethane coating materials are used more than waterborneones, they are inflammable and explosive, easy to volatilize organic compounds(VOC), and do harm to environment. Besides these, laws on controlling VOCemissions have been come up with by the international organizations. Therefore,people turn to waterborne polyurethane coating materials, which use water as basicdispersant. Waterborne polyurethane(WPU) coating materials have vast potential forfuture development because of non-flammable, light odor, environmental protection,energy conservation, easy operation etc.In this study, TDI and N220are used as the basic materials, DMPA as thehydrophilic monomer, diglycol as the chain extender, TEA as the salt forming agent,and acetone as the viscosity reducer. The PU pre-polymer is synthesized byprepolymer method, then WPU latex can be got after PU pre-polymer is put intowater. Analyze the structure of WPU coating film through Fourier transforminfrared spectroscopy(FT-IR). Making coating films on tinplate, glass slide and PET,and then a series of performance tests are done on these coating films. Experimentalresults show that, WPU coating film has poor adhesive power and water resistance.In order to improve adhesive power and water resistance of WPU, this paper usetwo aspects to modify WPU. One aspect is to add hydrophobe components into thesystem, and another aspect is to put in polar groups which can be reacted withhydrogen bond in the process of WPU latex forming coating film. Thus waterresistance will be reduced by enhancing the degree of cross-linking. Differentpercentage composition of silicone acrylic emulsion, fluorocarbon resin, silanecoupling agent, amino-silicon oil, graphene oxide(GOs) are chosen and be mixedwith WPU. And then, using these composite emulsion to make coating films on three above-mentioned substrate. Next step is to observe appearance of coating films byscanning electron microscope and to analyze structure by FT-IR. Lastly, test theproperties such as adhesion, contact angle, water absorption, viscosity, heat stabilityand so on. The experiment result indicates as follows: the water absorption is low,about18.19%when the percentage composition of silicone acrylic emulsion is3%,however the adhesive power level can reach Grade1when the percentagecomposition of silicone acrylic emulsion is4%and5%. When the percentagecomposition of fluorocarbon resin is7%, the effect is best, and water absorption is11.80%and adhesive power level is Grade1. The adhesive power level can reachGrade1, and water absorption is16.64%when the percentage composition of silanecoupling agent is3%.The effect of amino-silicon oil modifies WPU is not obvious.Neither does the GOs. However, the coating films of GOs/WPU have no foamingphenomenon, and the surface of films is smooth. What’s more, the heat stability isalso improved before unmodified one. |
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