Size and shape characterization of fines and fillers - a review

Many properties of fines and fillers are dependent on their size and shape. This review is on the literature on size and shape characterization of fines and fillers. It takes into account measurement techniques of particle width, length, equivalent diameter, area, and shape/morphology. The advantages and limitations of different methods are discussed. Measurement of other particles properties, e.g., optical, chemical or rheological, were not included in the review. Size and shape characterization methods can be roughly divided into gravimetric and non-gravimetric methods. Gravimetric measurements methods account for all particles in the sample, but give only indicative size and shape information. Non-gravimetric methods usually give more direct size and shape information, but only account for particles larger than the resolution of the instrument. Additionally, measuring both larger and smaller particles simultaneously is rarely possible. An implication is that current analysers fail to measure a larger share of the sample, for example fibrils, which have a high impact on product properties. Of the reviewed measurement techniques, flow microscopy had the highest potential. Based on instruments found in other application areas, possible developments for flow microscopes include multiwavelength illumination and sensors, fluorescent staining, and hydrodynamic focusing.