两种水性聚氨酯涂层在3种加速老化试验中的性能对比

Property Comparison of Two Water-based Polyurethane Coatings in Three Accelerated Aging Experiments

目的研究目前水性涂料中两种应用广泛的水性脂肪族聚氨酯涂层与水性丙烯酸聚氨酯涂层的耐候性与防腐性能的差异,探讨加速老化方法对涂层性能的影响。方法利用3种加速老化试验(中性盐雾、紫外-冷凝以及中性盐雾-紫外冷凝循环试验)对涂层进行240 d的加速老化。通过涂层的失光率、色差以及红外吸收光谱变化,研究涂层老化情况。利用交流阻抗法判断涂层防腐性能强弱,分析两种涂层体系在不同加速老化试验中的性能变化。结果在各加速老化试验条件下,水性脂肪族聚氨酯涂层相比于水性丙烯酸聚氨酯涂层,失光率与色差变化小,阻抗下降较少,涂层基体官能团分解程度小,说明水性脂肪族聚氨酯涂层老化程度小,防腐性能更好。3种老化加速试验对涂层阻抗影响顺序为:中性盐雾试验>循环试验>紫外-冷凝试验。对涂层色差、失光率影响顺序为:紫外-冷凝试验>循环试验、中性盐雾试验。结论连续的盐雾渗透对涂层的防腐屏蔽性能影响最严重。紫外线对涂层官能团分解具有加速作用,是涂层老化的主要原因。水性脂肪族聚氨酯涂层比水性丙烯酸聚氨酯涂层具有更好的耐候性以及防腐性能,可以应用在强紫外线、高湿热的环境。

This paper studied the difference in corrosion resistance of two kinds of water-based aliphatic polyurethane and water-based acrylic polyurethane coatings,which are widely used in water-based coatings.The effect of accelerated aging methods on coating performance was discussed.Three tests(neutral salt spray,UV-condensation,and neutral salt spray-UV condensation cycle test)were used to accelerate the aging of the coating for 240 days.Study the aging of the coating through the loss of light,color difference,and infrared absorption spectrum changes;Use the AC impedance method to judge the anti-corrosion performance of the coating,and analyze the performance of the two coatings in different accelerated aging tests.The results show that the water-based aliphatic polyurethane coating has smaller changes in gloss loss and color difference,less impedance reduction,and weaker decomposition of the functional groups of the coating matrix compared with the water-based acrylic polyurethane coating.Aliphatic polyurethane coating has lower aging degree and better anti-corrosion performance.The order of the three kinds of accelerated aging tests on the coating AC impedance is:neutral salt spray test>cycle test>ultraviolet-condensation test;the order of influence on the color difference and loss of the coating is:ultraviolet-condensation test>cycle test,neutral salt fog test.Therefore,continuous salt spray penetration has the most serious impact on the shielding performance of the coating;Ultraviolet rays accelerate the decomposition of the functional group of the coating matrix,which is the main reason for the aging of the coating.Water-based aliphatic polyurethane coating has better weather resistance and corrosion resistance than water-based acrylic polyurethane coating,so it can be used in environments with strong ultraviolet rays and high humidity.