| In terms of the mechanical strength, anti-aging,corrosion resistance and other performance requirements for polyurethane elastomer coating in areas such as bridges, dams and marine corrosion, in this paper, combined with the development trend of environmental protection and energy conservation, a solvent-free polyurethane elastomer coating with high-performance was prepared based on the actual background.The experimental study was made on the effects of different raw materials and reaction conditions on the properties of the polyurethane prepolymer.The results showed that 4,4'-dicyclohexylmethane diisocyanate(HMDI) and polymer diol can react with the use of catalyst. The order of the reactivity between polymer diol and HMDI containing the catalyst and the corresponding prepolymer viscosity was:polycaprolactone diol(PCL)1000 > polytetrahydrofuran diol(PTMG)1000 > polyoxypropylene glycol(PPG)1000. The optimum prepolymerization temperature was(80 ± 3) ?, the optimum reaction time for PTMG1000 and PCL1000 was 2h ~ 2.5h, PPG1000 was 3~3.5h.The prepolymer viscosity decreased with the amount of isocyanate increased.Verified by the single factor test of the relationship between polyurethane elastomer properties and molecule structural, PPG- type polyurethane elastomer was softer, PTMG- type was rigid, PCL-type was of good overall mechanical properties. With the increase of prepolymer isocyanate(-NCO) content, elastomer elongation at break decreased, strength rose to a peak followed by a gradual reduction; the amount of crosslinking agent(SGN) increased, strength and hardness rose to a peak followed by a gradual reduction, breaking elongation decreased; the smaller the steric hindrance of substituent molecular structure of poly-aspartate resistance, the smaller correspondsing elastomer tensile strength. A good elastomeric coating with overall performance could be obtained when the prepolymer-NCO content is 8.5%, SGN content is 0.3%, the chain extender is F420.In this paper, the polyurethane elastomer coating prepared with high solid content, appropriate two-component coating operation time and drying time. After curing, the coating had excellent flexibility and impact resistance as well of high strength and hardness, good elasticity; and strong adhesion to Q235 steel substrate. After 2000 h salt spray and 30 d media immersion test,no blistering or loss and other damage appeared on the coating,no rust appeared on the steel substrate surface; After 30 d medium immersion, the decrease rate of the coating adhesion to the substrate and tensile strength of the coating itself was no more than 10%. The polyurethane coatings prepared had long-term corrosion resistance.The UV aging properties of the polyurethane elastomer was tested. After UV 500 h, HMDI-PTMG1000 elastic coating gloss decrease rate was 8.11%, the color variation value ?E was only 1.57, the tensile strength of the coating decresed by 8.55%, the elongation at break dropped 10.71 %, no cracking or chalking appeared; the aromatic MDI-PTMG1000 elastomeric coating color turned from transparent to dark tan, gloss decrease rate was 59.43%, the color change value ?E was 7.01, the tensile strength decrease rate was 9.83%, elongation at break decline rate was 12.47%. Different aging times of polyurethane infrared spectroscopy showed that the urea bonds in polyurethane molecules are easy to break under ultraviolet light, while urethane bond has good anti-ultraviolet aging performance. |
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