Silica-reinforced epoxy shell phase change microcapsules for thermal regulation and mechanical enhancement of deep-water cementing composites

Excessive heat release during cement hydration in deepwater cementing operations can readily cause thermal decomposition of natural gas hydrates, leading to gas blowout incidents that compromise cementing quality. Incorporating phase change materials (PCMs) into deepwater cementing slurry systems effectively addresses this issue by regulating hydration temperatures. However, traditional PCMs suffer from insufficient mechanical strength and poor interfacial compatibility, leading to severe deterioration of cement mechanical properties. This study prepared nanoscale hybrid shell phase change microcapsules (MS@EPNS) with high-strength three-dimensional network structures. Silica nanoparticles were innovatively generated in-situ on the epoxy shell surface through a molecular bridging strategy to form crosslinks. Compared with epoxy shell microcapsules, MS@EPNS showed significantly enhanced mechanical strength (Young's modulus 4.13 GPa), thermal storage performance (186.6 J/g), and thermal stability. Results demonstrate that MS@EPNS exhibits excellent thermal regulation capability. The addition of 7 % MS@EPNS reduced hydration induction time by 6 %, while decreasing hydration temperature by 9.2°C. Qualitative and quantitative analyses revealed that MS@EPNS could induce preferential growth of calcium silicate hydrate on its surface, achieving secondary encapsulation of the microcapsules and significantly enhancing interfacial bonding strength, ultimately forming composite cement materials with low porosity and high strength. The cement stone containing 5 % MS@EPNS exhibited compressive strength increases of 27 % and 26.8 % after 3 days of curing at 20°C and 10°C, respectively. The prepared microcapsules successfully achieved synergistic optimization of mechanical properties and thermal regulation functions in cement composites, providing new insights for the development of high-performance deepwater cementing slurry systems.