Wedin Pär, Martinez Carlos J, Lewis Jennifer A, Daicic John, Bergström Lennart
YKI, Institute for Surface Chemistry, P.O. Box 5607, SE-11486 Stockholm, Sweden.
J Colloid Interface Sci. 2004 Apr 1;272(1):1-9. doi: 10.1016/j.jcis.2003.12.030.
Stress development during drying of coatings produced from aqueous dispersions of calcium carbonate particles in the presence and absence of organic binders was studied using a controlled-environment stress apparatus that simultaneously monitored drying stress, weight loss, and relative humidity. Specifically, the influence of two organic binders on drying stress evolution was investigated: (1) carboxymethylcellulose, a water-soluble viscosifying aid, and (2) a styrene-butadiene latex emulsion of varying glass transition temperature. The stress histories exhibited three distinct regions. First, a period of stress rise was observed, which reflected the capillary tension exerted by the liquid on the particle network. Second, a maximum stress was observed. Third, it was followed by a period of either stress decay or rise depending on the organic species present. Significant differences in stress histories were observed between coatings containing soluble and nonsoluble binders. Maximum drying stresses (sigmamax) of 0.2-0.5 MPa were observed for coatings produced from pure calcium carbonate or calcium carbonate-latex suspensions, whereas coatings with carboxymethylcellulose exhibited substantially higher sigmamax values of 1-2 MPa. Upon drying, these coatings were quite hygroscopic, such that cyclic variations in relative humidity induced large cyclic changes in residual stress.
使用一种可控环境应力装置研究了在有和没有有机粘合剂的情况下，由碳酸钙颗粒水分散体制备的涂层干燥过程中的应力发展，该装置可同时监测干燥应力、重量损失和相对湿度。具体而言，研究了两种有机粘合剂对干燥应力演变的影响：（1）羧甲基纤维素，一种水溶性增稠助剂，以及（2）具有不同玻璃化转变温度的丁苯胶乳乳液。应力历程呈现出三个不同的区域。首先，观察到一个应力上升期，这反映了液体对颗粒网络施加的毛细管张力。其次，观察到最大应力。第三，随后是一个应力衰减或上升期，这取决于存在的有机物质种类。在含有可溶性和不溶性粘合剂的涂层之间观察到应力历程存在显著差异。由纯碳酸钙或碳酸钙 - 胶乳悬浮体制备的涂层观察到的最大干燥应力（σmax）为0.2 - 0.5MPa，而含有羧甲基纤维素的涂层表现出明显更高的σmax值，为1 - 2MPa。干燥后，这些涂层具有很强的吸湿性，使得相对湿度的循环变化会引起残余应力的大幅循环变化。
