Thermal Breakdown Mechanisms of Emulsion Explosives in Deep Mining

The longevity of emulsion explosives under extreme thermal conditions (up to 150 °C) is dictated by specific molecular-level degradation pathways, where surfactant headgroup reactivity, salt type, and chemical stabilizers determine interfacial integrity. Thermal breakdown mechanisms of emulsion explosives were investigated at temperatures up to 150 °C, analyzing the effects of surfactant chemistry and additives on rheological performance and interfacial stability. We demonstrate that at 150 °C, the heat-induced hydrolysis of ester headgroup emulsifiers severely degrades the interfacial surfactant film, causing interfacial film rupture, significant coalescence (∼50 μm drops), and subsequent crystallization. While heating breaks urea-containing emulsions through ammonia-induced interfacial weakening (increased G'), stability is tunable: sodium ions enhance thermal stability via strong Na⁺-PIBSA binding, whereas calcium ions induce rapid crystallization in the presence of urea. These findings establish the key degradation pathways to improve the high-temperature stability of explosive formulations.