Effects of starch nanoparticles on phase inversion of Pickering emulsions

摘要

Understanding the effects of interfacial additives such as surface-active nanoparticles on phase inversion of Pickering emulsions is important from a practical point of view. In this work, we studied the effects of surface-active starch nanoparticles on catastrophic phase inversion of Pickering emulsions by continuous addition of a dispersed phase. Two types of experimental-grade starch nanoparticles were used: hydrophilic starch nanoparticles (HSNP) and hydrophobic starch nanoparticles (HOSNP). The dynamic oil-water interfacial tension was measured using the pendant drop method at varying starch concentrations in the aqueous phase while the contact angles were measured using the sessile drop method of the Axisymmetric Drop Shape Analysis-Profile (ADSA-P). Both types of starch nanoparticles (HSNP and HOSNP) were effective in delaying the phase inversion of emulsions from water-in-oil (W/O) type to oil-in-water (O/W) type. This delay in phase inversion was directly correlated with the concentration of starch nanoparticles. The interfacial tension decreased as the drop aged at a given starch nanoparticle concentration. The contact angles for both types of starch nanoparticles were within the intermediate wettability range that confirmed the irreversible adsorption of starch nanoparticles at the oil/water interface leading to an increased stability of emulsions.