Fabrication and Curing Kinetics of Thermal Insulation Material Suitable for Deep-Earth Extreme Environments

In the extreme high-temperature (up to 150 °C) and high-pressure (up to 140 MPa) conditions of deep in situ condition-preserved coring devices, high-strength epoxy resin was selected as the insulation layer. The non-isothermal DSC method was employed at heating rates of 2.5, 5, 10, 15, and 20 °C/min, revealing that increasing the heating rate elevates curing temperatures, expands the curing range, and enhances curing rate and heat release. The curing kinetics were modeled using n-order and autocatalytic approaches, with the latter accurately describing the behavior. Optimized integration process conditions (80 °C/4 h + 150 °C/2 h + 180 °C/3 h) yielded epoxy with compressive strength of 204.47 MPa, initial thermal decomposition temperature of 345.9 °C, thermal conductivity of 0.246 W/m·K, and Tg of 193.04 °C (storage modulus 2.41 GPa at 150 °C). As insulation, it reduces rock core heat loss by 32.38% (8.78 × 104 J) and active heating demand by 44 W, enhancing system stability for in situ temperature preservation.