Fundamentals of Colored Pigments
Pigments are chemicals that absorb and scatter visible radiations, and are generally dispersed in a medium to create an appearance, known as color. There are over 800 commercially available pigments, about 90% organic (based on C, H, N, type elements) and the rest inorganic (based on metals like Fe, Ni, Cd, Pb, Cr, Bi etc), which offer a number of choices in shades, cost of use, and other properties. Formulator’s common dilemma is, “Pigments” what is good combination for what application? Organic pigments offer high chroma, bright hues, and a variety of opacity, durability and other key properties which determine their suitability in specific applications. Inorganic pigments on the other hand are opaque, have relatively dull hues and lower tinting strength, but good resistance to chemicals, and weathering properties. A combination of key organic and inorganic pigments is very important to achieve a most cost effective color recipe for the given application. Organic pigments, although relatively large in number, can be classified in two main chimerical types, Azo, and Polycyclic chemistries, however offer a number of choices in physical and chemical properties. Light & weather fastness, heat stability, opacity and other properties vary from poor to excellent depending on chemistry and particle size. It is very important to understand these limitations for proper selection of organic pigments for a given application. In this presentation, discussion will focus on, basic chemistry, physical and chemical properties, and a comprehensive guide to selection of organic pigments for your applications. Some important references are given below.
Useful Books about organic pigments
Industrial Organic Pigments – Production, Properties, Applications
W. Herbs & K. Hunger
High Performance Pigments
Editors – E. Faulkner and R. Schwartz