471620 Surface Chemical Modification and Its Effect on Dynamic Flow Properties
C.G. Jange; R. P. K. Ambrose
Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN
Powder flow properties are crucial parameters in handling and processing operations, including discharge from hoppers and silos, transportation, mixing, compression and packaging. Particle size, shape, density, and particle size distribution are some of the factors that influence the flow properties. The interparticle forces are highly dependent on surface properties of particles and may impact flow behaviour. van der Waals, electrostatic and capillary forces, and mechanical interlocking are the possible interparticle interaction that could exist between particles. This research quantified the effect of surface chemical composition on the powder flowability. Qualitative and quantitative understanding on the effect of surface chemical modifications on interparticle interactions and flow behavior remain poor in published literature. To study the general effect of surface composition on bulk flow properties of powders, samples of uncoated and coated glass beads with size range of 125 µm and 180 µm were used. Flow property measurements were performed using the FT4 Powder Rheometer with pre-consolidation stress from 1kPa to 9kPa. The samples were coated with gluten, starch, and fat before flow property analysis. The average values of unconfined yield strength (UYS), major consolidation stress (, cohesion index (C), flow function coefficient (ffc), and angle of internal friction, for 125 µm size uncoated glass beads were 0.25kPa ± 0.03, 2.50kPa ± 0.31, 0.09 ± 0.01, 20.27 ± 3.96, 18.66 ± 0.32, respectively. For 180 µm samples, the values were 0.23kPa ± 0.06, 2.35kPa ± 0.02, 0.08 ± 0.02, 30. 46 ± 10.58, 19.66 ± 0.52, respectively. Results indicated ‘easy flowing’ characteristics for both size ranges followed by a slight increase in ffc for particles in the range of 180 µm. Particle size of coated and uncoated glass beads were measured using G3-ID-Raman Spectrometer (Malvern Instruments, UK). In completion of this study, we expect to quantify the influence of surface chemical composition on the dynamic flow properties of particulate material.
Key words: Surface Composition; Flowability; Interparticle Forces