Using an added liquid to suppress drying defects in hard particle coatings

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:582

Article

Fischer, Steffen B.^1,2  Koos, Erin¹ 

[1] Katholieke Univ Leuven, Soft Matter Rheol & Technol, Dept Chem Engn, Celestijnenlaan 200f, B-3001 Leuven, Belgium

[2] Karlsruhe Inst Technol, Inst Mech Proc Engn & Mech, Karlsruhe, Germany

关键词: Drying;    Particle coatings;    Capillary suspension;    Stress measurement;    Lateral drying;    Corner flow;    Yield stress;    Shrinkage;    Uniform film;   

DOI  :  10.1016/j.jcis.2020.08.055

来源: Elsevier

【 摘 要 】

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 poly-mers, 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. (C) 2020 Elsevier Inc. All rights reserved.

【 授权许可】

Free