(293e) Analyzing Segregation in Free-Flowing Powders Using Near-Infrared Spectroscopy Along with a Novel Sample Preparation Technique

Powder segregation can lead to variations in composition and properties, resulting in inconsistent product quality, dosage variations, and challenges in achieving desired attributes for powder-based formulations and products. This phenomenon has significant implications across industries such as pharmaceuticals, food processing, chemical manufacturing, and powder metallurgy. The primary contributors to segregation include differences in the physicochemical properties of the constituents, including particle size, density, shape, cohesion, etc. Despite its significance, segregation in fine powder mixtures is not well understood, and existing predictive models do not fully account for key segregation drivers. Moreover, current segregation testers require large quantities of materials and lack standardized validation, limiting their practicality in industrial applications.

This study aims to address these challenges by investigating segregation behavior in fine, free-flowing powder blends and with an ultimate goal of consolidating key segregation mechanisms into a unified framework. The major objectives include: (1) developing and validating a novel sample preparation technique that enhances the accuracy of segregation quantification, improves content uniformity assessment beyond the conventional relative standard deviation (RSD) methods, and minimizes material usage and sampling errors; (2) standardizing a Near-Infrared (NIR) probe-based segregation tester using disparate granular materials to ensure consistent, repeatable, and accurate results, (3) assessing the impact of particle property-based segregation drivers, including particle size ratio, density ratio, and shape, on segregation intensity of free-flowing powder blends.

A new sample preparation technique, combined with the Near-Infrared (NIR) spectrometer, SPECTester, was designed and validated, demonstrating enhanced precision in assessing content uniformity and segregation trends. The method significantly reduced material requirements to a few tens of grams while minimizing sampling errors common in free-flowing powder analysis. The SPECTester accurately quantified the segregation tendencies, capturing particle property effects both qualitatively and quantitatively. Various fine, free-flowing powders were tested to span a range of particle properties, ensuring that binary blends exhibited measurable segregation tendencies. Results revealed that particle size ratio, density ratio, and aspect ratio significantly influence segregation behavior. Notably, the ratio of median particle size (d₅₀) and bulk density (ρ) between larger and smaller particles exhibited a strong linear correlation with segregation intensity, with additional contributions from powder cohesion and shape effects. The findings underscore the importance of controlling particle properties to mitigate segregation and achieve homogeneity in granular free-flowing systems. It is hoped that such efforts will help develop tools for predicting and managing segregation in industrial powder processing, enhancing blend uniformity and process control.