Dynamic image analysis is a method to determine the particle size distribution and particle shape of a sample by continuously photographing the silhouette of dispersed particles. In contrast to laser diffraction and DLS, particle shape and aggregation state can be determined by this measurement method. During a measurement, the sample constantly flows past a camera. The dispersed particles can move randomly, which means that the camera can view them from all sides and thus determine their actual shape and particle size. The instrument software then calculates all relevant parameters and results in order to describe the particle’s size and shape:
- Particle size
- Projection area
- Aspect ratio
- Feret diameter
- Area equivalent diameter of particle
The most accurate results are obtained in a size range of 1 µm to 1000 µm. Examples of particle size and shape analysis applications are the analysis of fractions of different samples (e.g., catalysts, granules, breakage studies, etc.), determination of particles’ angularity, or the prediction of flow and compacting behavior in dependence of particle size and shape. The ISO norm 13322-2:2006 describes image analysis methods, making it possible to use this method in highly regulated industries as well.
Dynamic image analysis is a fast measurement method, usually taking up to only five minutes. Not only particle size, but also shape parameters, such as aspect ratio or convexity, can be obtained. As for laser diffraction, a representative sample volume is required to obtain meaningful and accurate results. For this method, sampling errors are the main source of unreliable measurement results.