Journal of Colloid and Interface Science ( IF 9.4 ) Pub Date : 2020-08-17 , DOI: 10.1016/j.jcis.2020.08.055 Steffen B Fischer 1 , Erin Koos 2
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Hypothesis
Lateral accumulation and film defects during drying of hard particle coatings is a common problem, typically solved using polymeric additives and surface active ingredients, which require further processing of the dried film. Capillary suspensions with their tunable physical properties, devoid of polymers, offer new pathways in producing uniform and defect free particulate coatings.
Experiments
We investigated the effect of small amounts of secondary liquid on the coating’s drying behavior. Stress build-up and weight loss in a temperature and humidity controlled drying chamber were simultaneously measured. Changes in the coating’s reflectance and height profile over time were related with the weight loss and stress curve.
Findings
Capillary suspensions dry uniformly without defects. Lateral drying is inhibited by the high yield stress, causing the coating to shrink to an even height. The bridges between particles prevent air invasion and extend the constant drying period. The liquid in the lower layers is transported to the interface via corner flow within surface pores, leading to a partially dry layer near the substrate while the pores above are still saturated. Using capillary suspensions for hard particle coatings results in more uniform, defect free films with better printing characteristics, rendering high additive content obsolete.
中文翻译：
使用添加的液体抑制硬质颗粒涂层中的干燥缺陷。
假设
硬质颗粒涂料干燥过程中的侧向堆积和膜缺陷是一个普遍的问题，通常使用聚合物添加剂和表面活性成分解决，这需要对干燥的膜进行进一步处理。不含聚合物的具有可调节物理特性的毛细管悬浮液为生产均匀且无缺陷的颗粒涂层提供了新途径。
实验
我们研究了少量辅助液体对涂料干燥行为的影响。同时测量在温度和湿度受控的干燥室中的应力累积和重量损失。涂层的反射率和高度轮廓随时间的变化与重量损失和应力曲线有关。
发现
毛细管悬浮液均匀干燥，无缺陷。高屈服应力抑制了横向干燥，使涂层收缩至均匀的高度。颗粒之间的桥防止空气侵入并延长恒定的干燥时间。下层中的液体通过表面孔内的角流传输到界面，导致靠近基材的部分干燥层，而上方的孔仍处于饱和状态。将毛细管悬浮液用于硬质颗粒涂料可产生更均匀，无缺陷的膜，并具有更好的印刷特性，从而使高添加剂含量过时。
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