Microencapsulation of sulfur by calcium alginate

Abstract

AbstractThe sulfur blooms on surface of rubber compounds cause loss of the needed tack for formation of multiply articles like tires. Although insoluble sulfur can be used to mitigate this problem, it is expensive to manufacture with a complex and hazardous process. This work examines an alternative approach that involves microencapsulation of soluble sulfur in alginate‐based matrix. The formulations and procedures are developed and evaluated. Alginate crosslinking time, controlled temperature change (e.g., from 10 to 36°C), and the drying method were found to be critical to achieving high encapsulation efficiencies. The higher temperature (36°C) helped with the mass transfer limited removal of CS2 used for dissolving sulfur, and treatment of crosslinked beads with oil prior to air‐drying improved sulfur encapsulation. Formulated beads had higher than 65% sulfur content (>80%, oil‐free basis) with almost 90% of the beads being <150 μm. The process parameters can be adjusted to make even smaller beads.