Colorants pearlescent

The colors found in industry today can be grouped into four main categories of finishes solid or straight shade colors, metallic colors, pearlescent colors and special effect colors. Any... 

Have a pleasant appearance (color, pearlescence, and a good viscosity). 

Colorability is another reason IDs select plastics for many products. Molding color into a product eliminates finishing and painting operations, thus reducing costs. Beyond cost, integral color also masks the nicks, chips and scratches that impair appearance during the life of the product. Color effects are almost limitless. Transparent, translucent, pearlescent, fluorescent, or marbleized colors are readily available for use in plastics. 

Colorants have been developed for special effects. Pearlescent or iridescent give an attractive appearance. They are often used for coating paper (e.g., cosmetic packaging). The pigment consists of thin platelets, less than 1 pm thickness, which have a high refractive index, e.g., mica coated with Ti02. 

Pearlescent pigments contain small flakes or platelets of the mineral mica that are additionally coated with a very thin layer of titanium dioxide. The simultaneous reflection of light from many layers of small platelets creates an impression of luster and sheen. By varying the thickness of the coating on the surface of the mica particles, pigment manufacturers can achieve a range of colors for the pearlescent effect. 

The presence of mica in pearlescent pigments only partly accounts for the appearance of the pigment. A very thin layer of the inorganic oxide titanium dioxide (TiC>2) or iron oxide (Fe2C>3) or both is coated on the mica platelets. The various colors and pearlescent effects are created as light is both refracted and reflected from the titanium dioxide layers. The very thin platelets are highly reflective and transparent. With their plate-like shape, the platelets are easily oriented into parallel layers as the paint medium is applied. Some of the incident light is reflected... 

Microscopic photo of pearlescent paint, http //www.standox.de/standote/englisch/color/3schicht.htm... 

Synthetic or natural pigments used to achieve lustrous, brilliant, or iridescent color effects by interference on thin optical films are called nacreous or pearlescent pigments [5.190]—[5.194]. They were originally used to simulate the appearance of... 

The development of the mica-based pigments started with pearlescent colors (Fig. 76 A, TiOz - mica). It was followed by brilliant, mass-tone-colored combination pigments (i.e., mica, Ti02, and another metal oxide) with one color (interference color same as mass tone) or two colors (interference and mass tone different) that depend on composition and viewing angle (Fig. 76 B). In the 1980s further development was made by coating mica particles with transparent layers of iron(III) oxide (Fig. 76 C) [5.222]. 

For known refractive indices, the maximum and minimum intensities of the reflected light, which are seen as interference colors, can so be calculated. The results are in good agreement with experimental data. Refractive indices of materials playing an important role for pearlescent pigments are listed below ... 

Practically applied platelet-like crystalline materials are produced with layer thickness (d) which are necessary to obtain the desired interference colors (iridescence) [11], Most of the pearlescent pigments synthesized today consist of at least three layers of two materials with different refractive indices. A simplified structure of such pigments and their interaction with light is shown in Fig. 15.4. For the case of metal oxide-mica pigments, thin flakes of mica (thickness ca. 500 nm, compara-... 

The most common class of pearlescent pigments today is based on thin platelets of mica (see Fig. 15.5). Mica itself is a natural mineral and belongs to the sheet layer silicates. Nacreous pigments are usually based on natural, transparent muscovite and only in some cases on synthetic phlogopite. Muscovite occurs worldwide, but only few deposits are suitable for pigment production. Mica is biologically inert and approved for use as a filler and colorant. 

Colorant A pigment, dye, or other chemical that imparts color (including black and white) or any special effect appearance to a polymer. These special appearances could be metallic, pearlescent, stone and fleck, flourescent, phosphorescent, thermochromatic, or photochromatic. 

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