Three kinds
of waxy oils that were identified by the three different surfactant
compositions, 0.5 wt % Span 80, 0.25 wt % Span 80 + 0.25 wt % Span
60, and 0.5 wt % Span 60, were prepared. Based on the mass of the
oil phase, 5.0 wt % paraffin wax and 0.5 wt % surfactant were mixed
into the mineral oil. All materials were then heated to 65.0 °C
for 2 h to ensure that all substances were fully dissolved in the
mineral oil. After that, waxy oils were obtained.
For emulsion
preparation, waxy oil was gradually cooled down to 35.0 °C and
maintained at this temperature for 30 min. Then, based on the volume
of waxy oil, water that was also heated to 35.0 °C was gently
poured into the oil phase with a volume ratio 20.0 vol %. A stirring
speed of 500 rpm was applied by an IKA stirrer (Eurostar 20 digital,
IKA, Germany) for 15 min to emulsify oil and water phases. Afterward,
three waxy oil emulsions were obtained, which were also marked by
the surfactant compositions as 0.5 wt % Span 80-doped emulsion, 0.25
wt % Span 80 + 0.25 wt % Span 60-doped emulsion, and 0.5 wt % Span
60-doped emulsion. The drop test method was used to identify the type
of emulsion. The drop of each emulsion was dispersed in the mineral
oil but remained as drops on the surface of water, indicating that
all emulsions were water-in-oil emulsions.
of waxy oils that were identified by the three different surfactant
compositions, 0.5 wt % Span 80, 0.25 wt % Span 80 + 0.25 wt % Span
60, and 0.5 wt % Span 60, were prepared. Based on the mass of the
oil phase, 5.0 wt % paraffin wax and 0.5 wt % surfactant were mixed
into the mineral oil. All materials were then heated to 65.0 °C
for 2 h to ensure that all substances were fully dissolved in the
mineral oil. After that, waxy oils were obtained.
For emulsion
preparation, waxy oil was gradually cooled down to 35.0 °C and
maintained at this temperature for 30 min. Then, based on the volume
of waxy oil, water that was also heated to 35.0 °C was gently
poured into the oil phase with a volume ratio 20.0 vol %. A stirring
speed of 500 rpm was applied by an IKA stirrer (Eurostar 20 digital,
IKA, Germany) for 15 min to emulsify oil and water phases. Afterward,
three waxy oil emulsions were obtained, which were also marked by
the surfactant compositions as 0.5 wt % Span 80-doped emulsion, 0.25
wt % Span 80 + 0.25 wt % Span 60-doped emulsion, and 0.5 wt % Span
60-doped emulsion. The drop test method was used to identify the type
of emulsion. The drop of each emulsion was dispersed in the mineral
oil but remained as drops on the surface of water, indicating that
all emulsions were water-in-oil emulsions.
