Colorants - Pigments and Dyes

An object that reflects only part of white light (between, say, 540 and 600 nm) appears yellow. Yellow light can also be generated by the 

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The object is the second part of our triad. Here we will discuss how materials interact with the energy from the light source. In this book we consider objects made of polymeric materials. Generally, polymers are colorless or at best weakly colored, and the aim always seems to be to cover up the undesirable color of the polymer in favor of the more desirable color selected by the designers. This requires the addition of colorants (pigments and dyes) to the polymer. The subject of colorants will be covered in depth in another chapter. However, because colorants become part of the object, we will first discuss some aspects of how they interact with light. 

Adhesives Organic and inorganic bases Coolants Cleaners colorants (pigments and dyes) Fragrances Inks Paints Plasticisers (e.g., in plastics) Polymers (rubbers and plastics) Sealants Solvents Stabilisers Synthetic fibres Varnishes Biocides Detergents Fertilisers Fuels Foodstuff additives and flavourings to foodstuffs Medicinal products (for humans and animals) Plant protection products Radioactive substances... 

Colorants n. Colored pigments and dyes. Color aptitude n. Ability to work with color, involving inborn factors as well as acquired abilities. 

This concludes the combustion portion of the text. Next we move into the world of colorants—pigments and dyes. These compounds, are the key ingredients in paints, inks, and dyes, and will lead us into an exploration of questioned documents and the world of trace evidence such as fibers. 

Colorants Pigments and dyes used to give color to plastic material. Provides any desired color. 

S. W. Souci, Z. Eebensm. Forsch. 108, 189—195 (1958). The Color Committee of the Deutsche Forschungsgemeinschaft. List of Pigments and Dyes for Cosmetics. Toxicological data on dyes and their suitabiUty for food in various countries. 

Colorants. This is often the determining feature of a plastic article. Two types of colorants are used pigments and dyes. Pigments are mostly inorganic... 

Addition of low levels of certain additives to PBT can be a desirable way to enhance properties. The most common additives are colorants. Both pigments and dyes can be used to color PBT. Carbon black and titanium dioxide are most widely used. Carbon black and other pigments, for example, phthalocyanines, can also act as a nucleant for speeding crystallization. 

Other studies have shown how monodispersed silica particles can be used as carrier material for pigments and dyes (68-73). Various reactive dyes, containing a sulfonic acid group, can be attached to the surface or incorporated into the growing silica particles (71). The resulting pigment particles have better color properties due to the con-... 

The metal effect depends not only on particle size and particle size distribution, but also on the orientation of the metal flakes within the coating film, particle shape, the transparency of the binder matrix, and the presence of colored pigments or dyes. 

Pigments and dyes provide paint and ink colors. Many highly toxic pigments, such as copper acetate (blue-green), arsenic trisulfide (yellow), and mercury II iodide (red), are no longer used. However, other hazardous pigment compounds, such as lead carbonate, mercury II sulfide, and cadmium sulfide, are still used today. These compounds present a danger to those artists who use their mouths to make a brush more pointed. 

Commercial anthraquinoid vat dyes are dye preparations that consist of a vat-table colored pigment and a dispersing agent. Such vattablepigments are polycyclic quinoid compounds that contain two or more carbonyl groups in a closed system of conjugated double bonds (Section 3.4). 

Both pigments and dyes have been used successfully as colorants. With liquid epoxy resins, inorganic pigments seem to provide optimal properties. Organic pigments are generally less effective with epoxy resins. 

Colorants are typically defined as pigments and dyes that, when added to plastics, define a specific color. The subject of colorants has been discussed in numerous books and papers. However, in the context of this chapter, a dye is defined as a substance that is soluble in the resin system and produces color only by the absorption of light and no scattering of light. Pigments are not soluble in the resin system and therefore must be mixed into the resin by one of many dispersion processes. Factors such as pigment particle size and ease of mixing or dispersion directly influence their... 

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