Pigments core-shell

Firstly it can be used for obtaining layers with a thickness of several mono-layers to introduce and to distribute uniformly very low amounts of admixtures. This may be important for the surface of sorption and catalytic, polymeric, metal, composition and other materials. Secondly, the production of relatively thick layers, on the order of tens of nm. In this case a thickness of nanolayers is controlled with an accuracy of one monolayer. This can be important in the optimization of layer composition and thickness (for example when kernel pigments and fillers are produced). Thirdly the ML method can be used to influence the matrix surface and nanolayer phase transformation in core-shell systems. It can be used for example for intensification of chemical solid reactions, and in sintering of ceramic powders. Fourthly, the ML method can be used for the formation of multicomponent mono- and nanolayers to create surface nanostructures with uniformly varied thicknesses (for example optical applications), or with synergistic properties (for example flame retardants), or with a combination of various functions (polyfunctional coatings). Nanoelectronics can also utilize multicomponent mono- and nanolayers. 

Fig. 9. The core shell pigment zircon red (top) consists of 90-95% shell (Si02-Zr02) and 5-10% core (color). The cobalt blue pigment (middle) and the black pigment (bottom) are much smaller. (Note the different magnification.)...

Vesely et al. [47] investigated organic coating properties dependence on chemical composition and structure of pigment particles. Metal oxide (MO)-based pigments (M = Zn, Mg) were synthesized with different particle shapes and core-shell pigments... 

For some applications the formation of compact films can be substituted by dispersing polymer pigments in a polymer coating. Instead of pigments for purely conducting polymers, modified pigments have been developed that are based on a core-shell concept. ... 

Kalendova, A. and Vesely, D. Study of the anticorrosive efficiency of zincite and peri-clase-based core-shell pigments in organic coatings. Progress in Organic Coatings, 4(1), 5-19 (2009). 

Core/shell particles have been described that may be used as special effect pigments for use in coatings, paints and inks (16). With respect to their cores, the particles may have a regular arrangement and are based substantially on high molecular polymers. The par-ticulated pigments may be applied to the substrates in the form of solid, liquid or paste preparations with the aid of auxiliary constituents and additives. 

Further, an inkjet method has been described wherein the inkjet recording material such as paper or plastic comprises a top layer containing core-shell particles of a refractive nature (17). Preferred pigment particle sizes are 0.005-0.3 jum. 

Generally, the film formation and pigment binding qualities of core/shell polymers are inferior to solvent coalesced systems and their use should be restricted to interior coatings or highly bound external paints such as gloss wood finishes and varnishes. 

Acrylic core-shell polymers have been used as principal pxjlymers for aqueous metallic basecoat paints [37—40]. The anionic shell allows pseudoplastic flow behavior which ensures parallel orientation of the aluminium pigments in the wet paint film. This orientation and the low solids content are responsible for the metallic gloss and high color flop (change in color observed on varying the viewing angle) of the basecoats. 

Coated particles are of interest for investigations involving catalysis, medicine and pigment production. The coatings which can be used to modify the properties of the underlying Fe oxide, may consist of a continuous, uniform shell around the core particle, or may be made up of very small particles that adhere to the core. 

Pigmentation of tablet core tablet coating gelatin capsule shell... 

Microcapsules containing polymer and pigment were prepared in [299] by dispersing a viscous suspension of pigment and oil-soluble shell monomer forming o/w emulsions. Subsequently, a water-soluble shell monomer was added to the emulsion droplets, encapsulating them via interfacial polycondensation. These microcapsules were then heated for free radical polymerisation of the core monomers. It has been shown that polyvinyl alcohol (PVOH) used as stabiliser reacts with the oil-soluble shell monomers. The decrease of PVOH concentration as result of this interaction leads to coalescence of the particles and to the increase of their equilibrium particle size, however, methods are proposed to prevent the depletion of PVOH. 

Core materials in microcapsules may exist in the form of either a solid, liquid or gas. The core materials are used most often in the form of a solution, dispersion or emulsion. Compatibility of the core material with the shell is an important criterion for enhancing the efficiency of microencapsulation, and pretreatment of the core material is very often carried out to improve such compatibility. The size of the core material also plays an important role for diffusion, permeability or controlled-release applications. Depending on applications, a wide variety of core materials can be encapsulated, including pigments, dyes, monomers, catalysts, curing agents, flame retardants, plasticizers and nanoparticles. 

Figure 68 Yield stress of composite particle with 1,3-butylene glycol dimethacrylate/butyl acrylate copolymer core and titanium hydroxide and phthalocyanine blue pigment shell dispersed in silicone oil (15 voI%) vs. the...

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