Flowability of Cellulose Powder Depending on the Morphology and Hydrophobicity

Flowability is an essential property that must be evaluated to ensure smooth and consistent feeding of powder materials into hoppers. It can be influenced by particle shape, size and its distribution, and surface chemical characteristics. In the case of cellulose powders, their physical and chemical properties are not uniform and can vary depending on the cellulose source and powder preparation method. In this study, the flowability of cellulose powders was evaluated through static and dynamic analyses. The angle of repose was measured to assess static flow characteristics, while avalanche behavior was analyzed using a revolution powder analyzer. Cellulose nanofiber, microcrystalline cellulose, and milled kenaf pulp were classified by particle size to investigate the effects of morphology. Larger and more spherical particles exhibited superior flowability, whereas particles smaller than 70 µm showed a sharp decline in flowability. Particle size had a stronger influence than size distribution. Increasing moisture content improved the flowability of fine particles but reduced that of coarse ones. Moderate hydrophobization enhanced flowability by reducing surface energy, whereas excessive treatment caused deterioration due to aggregation. These results identified the key parameters governing cellulose powder flow and clarified the characteristics advantageous for stable feeding and uniform product quality.