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Absorption Pigment Cores for Pearlescent Pigments

Title data

Matejdes, Marián ; Hausner, Josef ; Grüner, Michael ; Kaupp, Günter ; Breu, Josef:
Absorption Pigment Cores for Pearlescent Pigments.
In: Clays and Clay Minerals. Vol. 68 (2020) Issue 5 . - pp. 428-435.
ISSN 1552-8367

Abstract in another language

A lustrous appearance and interference-based colors make pearlescent pigments attractive for use in applications such as automotive paints, plastics, consumer electronics, and cosmetics. A combination of interference and absorption in the visible light spectrum improves significantly the hiding power as well as the color strength of pearlescent pigments while potentially extending their color range. The aim of the present study was to introduce synthetic fluorohectorites, having an appreciable diameter (similar to 20 mu m) and aspect ratio (similar to 1000), as promising colored cores for pearlescent pigments. Fluorohectorites can adopt a variety of colors by ion-exchange reaction with cationic organic dyes of high absorption coefficient. Unlike related dye-exchanged natural montmorillonite clays, which undergo acid activation accompanied by release of dye at low pH, as is required for subsequent coating with TiO(2)in an environment with low pH and elevated temperature, no leaching was observed with dye-exchanged synthetic fluorohectorites ([Na-0.5](int.)[Mg2.5Li0.5](oct.)[Si-4](O10F2)-O-tet.). Due to its significantly greater layer charge, more organic dye molecules were adsorbed per volume of the fluorohectorite than for montmorillonite. Consequently, the free volume available in the interlayer space for H(3)O(+)diffusion was less for synthetic fluorohectorite than for montmorillonite. Acid attack via interlayer space was, therefore, retarded significantly for fluorohectorite. Acid attack from the external edges of synthetic fluorohectorites was in the range of conventionally applied mica pigment core (fluorophlogopite, ([K](int.)[Mg-3](oct.)[AlSi3]O-tet.(10)(F,OH)(2)) because of the comparable large diameter of the platelets. Montmorillonite, however, occurs with particle diameters typically <200 nm and the much increased relative contribution of edges to the total surface area also makes them more prone to acid attack and concomitant leaching. Aside from leaching stability, the confinement of organic dyes in the interlayer space restricts rotational and vibrational motions, which in turn stabilizes the dyes typically by similar to 100 degrees C against thermal decomposition as compared to chloride salts of the dyes.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: Absorption cores; Acid stability; Natural montmorillonite; Pearlescent pigments; Synthetic fluorohectorite; Thermal stability; ACID ACTIVATION; LAYER CHARGE; NANOPLATELETS; MINERALS; CAPACITY; DYES
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry I > Chair Inorganic Chemistry I - Univ.-Prof. Dr. Josef Breu
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 06 Apr 2023 06:29
Last Modified: 06 Apr 2023 06:29