Time-Dependent Rheological Behavior of Surface-Coated Calcite Powder: Implications for Industrial Applications

In this study, the effects of stearic acid coating concentration (0.85%, 1%, and 1.15% wt.) and storage duration (up to 30 days) on the flow properties of surface-modified micronized calcite powder were investigated to evaluate their implications for critical industrial processes including transportation, feeding, dispersion, and production capacity. The results demonstrated that both stearic acid concentration and storage duration significantly influenced the rheological properties of the coated calcite powders, suggesting that the calcite surfaces had dynamic characteristics. The Conditioned Bulk Density (CBD) values increased significantly from day 1 to day 30, indicating efficient packing of the powders. Although stearic acid-coated calcite powders initially demonstrated enhanced flowability (SE: 5.1→3.7 mJ/g; BFE: 77→59.3 mJ) within the first 8 days, a subsequent increase (SE: 4.6 mJ/g; BFE: 74.3 mJ) by day 30 indicated a time-dependent surface reorganization of the coated particles. The reduction in the Flow Rate Index (FRI) values after a 30-day period indicated a decrease in cohesiveness. The stability index (SI) values initially indicated instability but improved after 30 days. These findings highlight the importance of considering the coating amount and time-dependent behavior when designing experiments, formulating products, and establishing quality control procedures involving calcite fillers.