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. However, the flowability of cellulose powders is difficult to predict due to their complex particle morphology and surface characteristics. In this study, the key factors affecting the flowability of cellulose powders, including particle size, shape, size distribution, moisture content, and surface chemistry, were investigated using cellulose nanofiber, microcrystalline cellulose, and kenaf pulp. Both static and dynamic flowability were evaluated using angle of repose measurements and dynamic avalanche analysis. Among the morphological factors, the average particle size of cellulose powders was identified as the dominant parameter influencing their flowability. Flowability improved with increasing particle size and showed a sharp decline for fine particles smaller than 70 µm. With increasing moisture content, the flowability of fine particles smaller than 20 µm was improved, whereas that of relatively larger particles deteriorated. Hydrophobization enhanced flowability by reducing surface energy and friction. However, excessive hydrophobization induced particle aggregation and decreased flowability. These results identified the key parameters governing cellulose powder flow and clarify the characteristics advantageous for stable feeding and uniform product quality.