(21g) Surface Energy and Its Effect on Interparticle Interaction during Particle Flow

C.G. Jange¹; R. P. K. Ambrose²

¹Graduate Research Assistant; ²Assistant Professor, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana, USA.

The aim of this study is to understand the mechanism that drives the surface intermolecular interaction effects on dry cohesive powder flowability. Silica beads of 125 µm, 180 µm and 250 µm were coated with chemical components to mimic the intermolecular interaction of surface components present in common food products. The average Sauter mean diameter (d_3,2) of coated particles were 143.32 ± 8.92 for 125 µm, 176.21± 6.05 for 180 µm and 257.23 ± 2.57 for 250 µm, respectively. As per dynamic flow properties, the stability index for all samples ranged from 0.9 to 1.1, indicating stable powder flow. No significant sensitivity to change in flow rate was reported. An increment in specific energy was observed for all surface modified samples as compared to the control group, except for particles coated with molasses. Lower basic flow energy values were observed for particles coated with butter and molasses as compared to the control specimens. The surface modified samples presented higher compressibility percentages as compared to control systems. The angle of internal friction (AIF) also varied with surface composition and applied pressure. To investigate the influence of surface composition over kinematic performance, dispersive and polar contributions of the surface free energy of the solids were obtained using a surface energy analyser (SEA) . Heptane, octane, nonane, and decane were used as probe molecules based on an infinite dilution method. With the completion of this study, a granular Bond number based relationship will be developed to establish a relation between surface composition and powder flow.