Characterization of Rheological and Tribological Properties of Sodium Alginate Microspheres Prepared by High-speed Shear and Microfluidics

Sodium alginate microspheres have a wide range of applications in the fields of biomedicine and food industry. However, until now there is a lack of systematic discussion on the rheological and tribological properties of sodium alginate microspheres. In this study, sodium alginate microspheres with different particle size distributions were prepared using high-speed shear and microfluidic methods respectively, and dispersed the microspheres obtained at three concentrations of no packing (0.5 wt%), semi packing (5 wt%), and close packing (20 wt%) respectively in water to obtain suspensions. Particle size, morphology, rheological properties (flow properties, viscoelastic properties, thixotropic properties), and tribological properties were compared. Results showed that the microspheres prepared by the high-speed shear method had a particle size of 127.7±55.0 µm, while the microspheres prepared by microfluidic method had a more regular shape with the particle size of 91.2±3.3 µm. The microspheres prepared by the high-speed shear method exhibited stronger shear thinning behavior. In the low concentration range (0.5 wt%~5 wt%), the microspheres prepared by microfluidic method showed obvious viscous characteristics, while the microspheres prepared by the high-speed shear method showed obvious elastic characteristics. The microspheres prepared by microfluidics exhibited stronger thixotropy and recovery ability, and their tribological coefficient was less affected by the concentration. Overall, the microspheres prepared by microfluidic method had more stable rheological and tribological properties. This study is significant for understanding the impact of concentration and particle size distribution of sodium alginate microspheres on their rheological and tribological properties, and worthwhile for developing microsphere products with controllable rheological and tribological properties.