Effect of NaCl concentration on stability of a polymer–Ag nanocomposite based Pickering emulsion: validation via rheological analysis with varying temperature

Abstract

The utility of a Pickering emulsion (PEm) under saline conditions is strongly dependent on the stability of the emulsion in the presence of different salt concentrations. In this study, we have evaluated the effect of NaCl and temperature on the stability of a polyacryloyl hydrazide (PAHz)–Ag nanocomposite (NC) based PEm utilizing ocular observation, an optical microscope with a thermal stage, TGA, DLS, electrical conductivity, and rheological studies at different temperatures. The creaming stability of PEm in the presence of salt concentrations in the range of 0.5 to 5.0 wt% was evaluated by adding different amounts of PAHz–Ag NC stabilizer. The effect of NaCl on emulsion stability is strongly dependent on the aggregation behaviour of the nanocomposites, showing signs of aggregation at low NaCl concentration (<3 wt%) and re-dispersion at high NaCl concentration (>3 wt%). As per the microscopy analysis, 25 wt% of PAHz–Ag NC was sufficient to stabilize the PEm for a period of up to 7 days in the presence of salt concentrations up to 3 wt% in the aqueous layer at 95 °C. Thus, the balance of ionic strength provides an important insight into the nature of nanocomposite interactions in emulsion systems and a possible mechanism for designing emulsion properties via salt inclusion.