Enhanced ethanol retention and thermal stability in calcium chloride-stabilized ethyl cellulose gel fuels

The design of thermally stable, thixotropic gel systems with tunable mechanical properties is essential for advanced functional materials. In this study, ethanol-based ethyl cellulose (EC) gels were fabricated via incorporation of calcium chloride (CaCl2), and their microstructural, rheological, and thermal behaviours were systematically investigated. Ethanol–EC solutions form viscous liquids; however, CaCl2 induces gelation through a synergistic mechanism of ionic coordination with ethanol and cellulose chains, promoting a robust polymer network. At an optimal EC:CaCl2 ratio of 2:1 (sample EC100s50), oscillatory rheology confirmed a true gel state (G′ > G″ in the linear viscoelastic region, yield stress ≈ 115 Pa), accompanied by shear-thinning behaviour. Phase-contrast microscopy revealed a homogeneous, interconnected network, while thermogravimetric analysis indicated enhanced ethanol retention, with delayed evaporation up to 165 °C and single-step EC decomposition occurring at 312 °C. The activation energy for EC decomposition in the optimized sample (EC90s45) reached 185 ± 15 kJ mol−1, exceeding that of pure EC, yet ethanol was still released for ignition, with an activation energy of 45 ± 4 kJ mol−1 and a total combustion energy density of 29.3 kJ g−1. These results demonstrate that CaCl2-assisted ionic coordination is an effective strategy for engineering soft-solid ethanol–EC gels with tuneable viscoelasticity and thermal resistance, offering potential for applications in energy materials and propulsion-related functional composites.