Pigments and dyes are two colorants responsible for making our world so bright and colorful. Though the function of both is the same they differ in their properties and features. The main point of difference arises from their solubility feature. Putting it simply, if a color imparting material dissolves in a liquid like how sugar does in water then the material is called a dye. Pigments are color imparting powders that are not soluble in the liquid in which they are mixed.
There are varied types of dyes and pigments to suit the needs of varied industrial and commercial applications. The dye variety comprises of basic dyes, direct dyes, acid dyes, disperse dyes, synthetic dyes, natural dyes and sulfur dyes. Each class has a wide array of hues which are given specific names like acid red, basic blue, direct black and so on. The pigment class comprises of organic pigments, inorganic pigments, special effect pigments and functional pigments. The following brief discusses on pigments used for plastics and pigments for paints.
Pigments for Plastics
Plastics as we see them in almost every consumer application are colored. Incorporating color evenly throughout a moulded article as plastic is much easier than doing so in ceramics and metals. Pigments which are popularly used for coloring plastics include zinc oxide and titanium oxide which imparts white color; carbon to impart black color and several more inorganic oxides like chromium and iron. Organic compounds also impart color and these can take the form of either pigments or dyes. Dyes, however, have limited use as colorants in this industry as pigments provide more choices to the manufacturer. This is because of their broader chroma range and superior heat stability for a wide number of resins. The functionality of pigments today in the plastic industry is not limited to providing the required hue but it also touches upon in large measure, factors of sustainability, compliance and processability.
Pigments for Paints
A wide range of pigments go into the paint industry, including specialty pigments. The paint formulations which use pigments as the colorant go into applications that are either centered on the decorative aspect or the industry based applications. Industry based applications include automotive, aerospace, refinishing, coil and more.
Today, the rigorous regulatory demands with regard to use of pigments in paint formulations have led to development of newer techniques. Pigment powder preparations have to gear up to meet the stringent demands placed by regulatory authorities. Anti-corrosive, eco-friendly pigments that are economically feasible are increasingly used while formulating paints in the industry. Efforts are made to offer alternatives to anti-corrosive but carcinogenic chrome based pigments. There is more emphasis on using orthophosphate, polyphosphate, organic inhibitor, wide-range anti-corrosives for paint formulations. Calcium modified silica centered anti-corrosive pigments are setting the mark in paint formulations.
On a Concluding Note
The role of pigments and dyes in today’s world cannot be undermined. Pigments and dyes are the colorants that have made today’s world so much brighter and beautiful. In this context, the aspect of using eco-friendly pigments in all applications therefore, must not be forgotten.