水性双组分聚氨酯涂料的活化期研究

分别采用水性羟基聚丙烯酸酯分散体(PAD)和羟基聚丙烯酸酯乳液(PAE)与亲水改性多异氰酸酯固化剂配制水性双组分聚氨酯涂料(2K-WPU),通过黏度、硬度、光泽度和耐化学介质性能等测试,研究了2K-WPU在不同放置时间内的物理化学行为.结果发现:随放置时间的增加,PAD型2K-WPU的黏度降低,涂膜的起泡程度逐渐增加,涂膜硬度先降低后增加,3h后耐化学介质性能下降;PAE型2K-WPU的黏度变化无规律,涂膜硬度逐渐降低,4h后耐化学介质性能下降,气泡相对较少;PAD型和PAE型2K-WPU的粒径和光泽均无明显变化;PAE型2K-WPU的活化期一般在4h以内,而PAD型的更短,但涂膜的综合性能更优.因此施工前不能根据2K-WPU的黏度变化来判断其活化期,而须根据涂膜耐化学介质性能和外观变化来判断.

Investigation into Pot Life of Waterborne Two-Component Polyurethane Coatings

Waterborne two-component polyurethane (2K-WPU) coatings were prepared from hydrophilically-modified polyisocyanate reacting respectively with an aqueous hydroxy-polyacrylate emulsion (PAE) and its dispersion (PAD). Then, the viscosity, hardness, gloss and chemical resistance of the films were measured to investigate the physicochemical behaviours of 2K-WPU during the storage. The results indicate that (1) with the increase of storage time, the viscosity of PAD-based 2K-WPU slowly decreases, along with an increase in bubbles and micro-foams in the film, the film hardness first decreases and then increases, and the chemical resistance decreases after a storage for 3h;(2) as for PAE-based 2K-WPU, the viscosity disorderly changes, the film hardness gradually decreases, the chemical resistance decreases after a storage for 4h, and the bubbles in the film even disappear;(3) neither the particle diameter nor the gloss of PAE- and PAD-based 2K-WPU shows obvious change during the storage;and (4) PAD-based 2K-WPU is of better film performance but slightly shorter pot life than the PAE-based one (about 4h). It is thus concluded that it is not the viscosity but the chemical resistance and appearance of the film that determine the pot life of 2K-WPU before the application.