Home » Continuous-Imaging Fluid Particle Analysis in Coatings Research, Development and Production Applications: A Primer
Many scientific endeavors involve the use of particulate matter suspended within a liquid. Typically, these endeavors are a part of a "process" that is being studied for reasons of determining cause and effect during a discovery process, and later for monitoring the state of that particular process once something is known about the causes and effects. Typical examples include water quality analysis and monitoring, chemical process analysis and monitoring in manufacturing, and pure scientific research. A critical issue in these processes is the measurement and analysis of the particulate matter present in the process. In very few cases are the particles under study large enough to be quantified and analyzed by the naked eye. With the advent of the microscope, scientists were able to study some of these particles in great levels of detail. As technology has advanced over the years, with the introduction of instruments such as the Scanning Electron Microscope (SEM), scientists have been able to look at increasingly smaller particles - even down to the molecular level. This article will look at the issues associated with fluid particle analysis, discuss some of the historical methods used and introduce a new technology, the continuous-imaging fluid particle analyzer, which offers an automated method for particle analysis that can be used over a broad range of material types/sizes, both in the laboratory and in the field. Examples from the coatings industry will also be discussed.
While frequency (particle count per unit volume) seems to be fairly straightforward at first, it can be easily complicated by overlapping particles and "clumping" of particles. This potential problem is easily fixed by diluting the subject matter to separate the particles and presenting them in a single cell layer, enabling a straightforward "binary" analysis (particle is either present or it is not). The issue of how we characterize particles presents us with a much more difficult problem, however. For the purpose of analysis, it is usually desirable to quantify particle size as a "single number", which can be plotted against another variable (frequency, dilution, temperature, etc.) on a simple graph. The simplest measure of particle size would be its diameter, but even this is not as straightforward as one would think due to variations in particle shape. In a perfect world, all particles would be of the same shape, allowing a single number to be used to quantify size. But in the real world, particles exhibit a variety of shapes, and the problem becomes how to characterize the distribution of particle shapes. A fair amount of research and applied mathematics have been applied to this very problem1 and is beyond the scope of this article. The generally accepted industry norm for particle size is to calculate its Equivalent Spherical Diameter (ESD). This permits a single number to quantify the size of particles of any shape.
Our March issue features several articles on new bio-based technology available to coatings manufacturers. Other articles discuss new branched surfactants that improve tinting systems for architectural coatings; emerging trends impacting the global coatings market; and air-operated, double diaphragm pump technology.