(13b) Graphical Comparison of Image Analysis and Laser Diffraction Particle Size Analysis Data: a Demonstration of the Incorrect Assumptions of Random Particle Orientation and Equivalent Spherical Volume for Acicular Particulates

Since the commercial introduction of laser diffraction (LD) particle size analysis (psa) systems, interpretation of LD psa data has been characterized by confusion. Despite a decade long effort of particle characterization scientists and applied mathematicians to effect demystification, there still exists a general lack of appreciation in the user community of the limitations and the consequences resulting from these limitations of the assumptions made within the analysis algorithms of past and current generation LD psa systems, which include:

· Particles are spherical · Particles are optically homogeneous · No multiple scattering exists · Particles are randomly oriented in the measurement zone · Particle size estimators are expressed in terms of equivalent spherical volume diameters · Particle volume measurements are obtained

This status quo has been primarily responsible for the limited ability to verify LD psa results by means of comparison to results from an orthogonal technique such as image analysis (IA). When provision is made, however, for the limitations of the LD psa analysis algorithm assumptions, a straightforward graphical comparison can be made of LD psa and IA psa results.

The presentation will include; a review of the results obtained from LD and IA experiments conducted on materials of varying morphology, demonstrations of the application of an Excel macro set developed to facilitate the graphical comparison of LD and IA psa results, and a discussion of the frequent incorrectness of the random particle orientation and equivalent spherical volume diameter assumptions as revealed through experimental results.