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High hiding power and weather durability of film-coated titanium dioxide particles with a yolk-shell structure.

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Title: High hiding power and weather durability of film-coated titanium dioxide particles with a yolk-shell structure.
Authors: Liang, Yong1, Yu, Keyi1, Xie, Jiuren1, Zheng, Qinzhong1, Wang, Ting-Jie1 wangtj@tsinghua.edu.cn
Source: Colloids & Surfaces A: Physicochemical & Engineering Aspects. May2017, Vol. 520, p736-742. 7p.
Subjects: Titanium dioxide, Structural shells, Povidone, Durability, Metallic films, Surface coatings
Abstract: High hiding power and weather durability are the key characteristic indices of the high-performance pigmentary titanium dioxide (TiO 2 ). The film-coated TiO 2 particles with a yolk-shell structure of silica were prepared by surface-protected etching with polyvinyl pyrrolidone. The hiding power of the TiO 2 particles with the yolk-shell structure was 90.6, which is significantly higher than the hiding power of 87.7 for the dense film-coated TiO 2 particles with the same amount of coating (20%). However, the TiO 2 particles with the yolk-shell structure have low weather durability. The apparent degradation rate constant K app for rhodamine-B had a high value of 13.2. An improvement was made by coating a dense MgO film on the TiO 2 particles first, and then coating a yolk-shell structure. The hiding power of the TiO 2 particles with the improved yolk-shell structure reached 90.6, and the weather durability was significantly increased as the apparent degradation rate constant K app decreased to 2.2, reaching the excellent weather durability of the TiO 2 particles with 5 wt% dense film coating (Si3 + Al2), which is a common product in industry ( K app = 1.8). For the same indices of hiding power and weather durability, the TiO 2 particles with the improved yolk-shell structure obviously decreased the consumption of TiO 2 , compared with the dense SiO 2 -coated TiO 2 particles (TiO 2 @SiO 2 ). It is inferred that the void in the yolk-shell structure increased the light reflectivity of the TiO 2 particles by increasing the difference of the refractive index between the core TiO 2 and the surroundings, and the dense MgO film increased the weather durability of the TiO 2 particles. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:High hiding power and weather durability are the key characteristic indices of the high-performance pigmentary titanium dioxide (TiO 2 ). The film-coated TiO 2 particles with a yolk-shell structure of silica were prepared by surface-protected etching with polyvinyl pyrrolidone. The hiding power of the TiO 2 particles with the yolk-shell structure was 90.6, which is significantly higher than the hiding power of 87.7 for the dense film-coated TiO 2 particles with the same amount of coating (20%). However, the TiO 2 particles with the yolk-shell structure have low weather durability. The apparent degradation rate constant K app for rhodamine-B had a high value of 13.2. An improvement was made by coating a dense MgO film on the TiO 2 particles first, and then coating a yolk-shell structure. The hiding power of the TiO 2 particles with the improved yolk-shell structure reached 90.6, and the weather durability was significantly increased as the apparent degradation rate constant K app decreased to 2.2, reaching the excellent weather durability of the TiO 2 particles with 5 wt% dense film coating (Si3 + Al2), which is a common product in industry ( K app = 1.8). For the same indices of hiding power and weather durability, the TiO 2 particles with the improved yolk-shell structure obviously decreased the consumption of TiO 2 , compared with the dense SiO 2 -coated TiO 2 particles (TiO 2 @SiO 2 ). It is inferred that the void in the yolk-shell structure increased the light reflectivity of the TiO 2 particles by increasing the difference of the refractive index between the core TiO 2 and the surroundings, and the dense MgO film increased the weather durability of the TiO 2 particles. [ABSTRACT FROM AUTHOR]
ISSN:09277757
DOI:10.1016/j.colsurfa.2017.02.046