# Conditions for and Characteristics of the Dispersion of Gel Fuel Droplets during Ignition
## 3 Results and Discussion
Based on the experimental results, a hypothesis was formulated about the causes of the microexplosive dispersion of binary liquid droplets under their intense heating. This hypothesis is based on the thermodynamics of wetting, as well as the theory of two-component SFE. The SFE of the liquid-liquid interface formation in the general case can be defined as:  
\[\Delta G_{1,2}=\sigma_{1,2}-\sigma_{L1}-\sigma_{L2}=-2\bigg{[}\Big{(}\sigma_{ L1}^{D}\cdot\sigma_{L2}^{D}\Big{)}^{1/2}+\Big{(}\sigma_{L1}^{P}\cdot\sigma_{L2}^{P} \Big{)}^{1/2}\bigg{]} \tag{3}\]  
where \(\sigma_{1,2}\) is the interfacial tension at the liquid-liquid interface in N/m; \(\sigma_{L1}\) and \(\sigma_{L2}\) are surface tensions of liquids (components) #1 and #2, respectively in N/m. The surface free energy of the liquid-liquid interface formation had a negative value in the vast majority of the cases of the mixing of two liquids. Table S2 presents the values of the SFE of the liquid-liquid interface formation. The formation of the liquid-liquid interface is less energy-intensive than the formation of the liquid-gas interface from the point of view of thermodynamics. This is due to the fact that liquids have cohesive interactions between their molecules at the liquid-gas interface. There are no cohesive interactions between gas molecules. Molecules on the surface of a liquid tend to interact with any other liquid, but not gas molecules. The last statement was also valid in the case of mutually insoluble liquids when the components from the first group (polar liquids) and fourth group (dispersive liquids) were mixed. Let us consider the mixing of the components of these groups in more detail. Molecules of liquids belonging to the fourth group were only capable of relatively weak van der Waals interactions; in addition, they were capable of much stronger hydrogen bond interactions. Consequently, the molecules of the liquids from the first group would prefer to interact with each other than with the molecules of liquids from the fourth group. However, the molecules of the liquids in the first group at the liquid-gas interface were forced to interact with the gas (the environment, under the conditions of the experiments with air). Under the action of cohesive forces, the molecules of the liquids from the first group tended to lower the surface energy. Under such conditions, the inversion of the \"liquid-gas\" interaction into a liquid-liquid interaction occurred upon contact with any other liquid. This was true even when the interaction was conducted predominantly by van der Waals forces, as in the case of the liquids from the fourth group. Therefore, the SFE of the liquid-liquid interface formation when mixing components from the first and fourth groups would always be negative. It should be noted that the SFE of the liquid-liquid interface formation took on more negative values if two liquids were mutually soluble (capable of similar cohesive interactions)--for example, components belonging to the same group or components from the first and second groups. That is, the energy tended to the lowest values under conditions in which the liquids were characterized by close values of \(\sigma_{L}^{P}\) and \(\sigma_{L}^{D}\). Under the conditions of high-temperature heating, the heat supplied to the binary liquid droplets was spent on its heating and evaporation. As the droplets heated up, their temperature rose. As the temperature rose, the surface tension of the components that made up the mixture decreased. Consequently, the SFE of the liquid-liquid interface formation decreased. The condition for the formation of a vapor bubble on the liquid-liquid interface was a decrease in the SFE (under ideal conditions) and the implementation of isothermal conditions. This would occur when the heat accumulated in the droplet exceeded the heat spent to heat the droplet to the boiling point of the low-boiling component and compensated for the heat spent on the evaporation of the components that made up the droplet.