Applied Rheology in the Protective and Decorative Coatings Industry

The success of a wide range of commercial products and industrial processes depends on meeting specific flow requirements. Industrial applied rheology attempts to relate fundamental properties to fitness-for-use of fluids of commerce. Architectural and industrial coatings, molded plastics, adhesives, personal care products and cosmetics, inks, cement, drilling muds, ceramic slips, solder pastes, foodstuffs and medicines are examples of rheologically complex fluids whose commercial viability depends on having the “right” rheology. For such materials, the necessary rheological properties must be defined with due regard to the prevailing conditions of stress and strain rate in processing and application. Unfortunately, the predominant practice in industry with respect to rheological characterization is to rely on rugged but simple viscometers or “viscometry devices”. These typically measure within a limited range of stress or strain rate, generally returning arbitrary numbers of uncertain value. On the other hand, it is often very difficult to link fundamental rheological properties with “real-world” performance. The challenge to the applied rheologist is to design experiments having relevance to the process at hand and then usefully apply the result in other words, to bridge rheology and technology. This article discusses the use of, in particular, controlled-stress rheometry to characterize complex fluids, with the main thrust toward the coatings industry.