Most established particle size techniques assume all particles are round. In reality, most industrial particles are not — leaving critical information unmeasured.
Volume-weighted histograms emphasize the presence of larger particles, while number-weighted histograms reveal large quantities of fine particles that may cause clogging or filtration issues. Both views are essential for thorough characterization.
Irregular particle shape can significantly impact how particles interact with each other, how they flow, and how they compact, ultimately impacting the efficacy of final products. Because of this, many years ago, scientists embraced and elevated the characterization of particles based on shape and size by using direct measurement techniques such as microscopes. Although slow and tedious, microscopy allows users to obtain qualitative information about their raw materials particles even though it is practical to measure only a small population of particles.
It wasn’t until the early 1990s when improved machine vision cameras and higher performing computers were around to start analyzing the shape of particles in a more standardized way with a much higher sampling of particles. Image Analysis, whether the particles are static or dynamically moving, involves very fast image processing.
Commercial shape analysis systems began to appear on the market in the 1990’s and 2000’s. Approximately in 2014, new add-on shape analysis systems, such as the Particle Insight Shape Module, were developed to attach to existing size-only instruments as a shape complement. From this, shape analysis has become known as a complementary method to different size-only techniques.
Dynamic image analysis is a number-based technique — it measures particles individually. Because of this, it can report particle size in both number-weighted and volume-weighted distributions. Having accurate results of both is critical: monitoring fine particles impacts flowability and filter clogging, while volume-weighted data identifies agglomerates or large particles that can impact the final product.
Equivalent Circular Area Diameter — Histogram & Statistics
Number-Weighted Distribution
Volume-Weighted Distribution
Because dynamic image analysis is number-based, every particle is represented on the histogram with thumbnail images.
By only looking at a size histogram, an analyst might think all particles are in the 50-micron range. In fact, the sample may be made of three different shaped particles — all measuring ~35 microns in size-only data. These different shapes will blend, compact, flow, and behave differently in a process.
Size histogram hides shape differences
Thumbnails reveal three distinct particle types
Dynamic image analysis gives thumbnail images of every measured particle. Besides making 30+ shape measurements, the ability to see thumbnails as objective evidence eliminates the need for an expert to make decisions based only on statistical graphs and numerical data.
Size histogram hides shape differences
Thumbnails reveal three distinct particle types