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.

The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical volume fraction of water where phase inversion from W/O to O/W emulsion took place was determined through conductivity measurements. Cetyltrimethyl ammonium bromide (CTAB) was used as a surfactant to modify the nanoclay. The adsorption of CTAB onto nanoclay had a strong influence on the contact angle and the critical volume fraction of water where phase inversion took place. The modification of the nanoclay brought about by the adsorption of CTAB increased the three-phase contact angle (measured through the aqueous phase), thereby making it more hydrophobic, and prolonged the phase inversion point. CTAB alone and CTAB-modified nanoclay delayed the phase inversion process in a similar manner, showing a strong dependence on the CTAB concentration.