Slow Curing of Epoxy Resin Underwater at High Temperatures

Abstract

Epoxy resins have been widely applied in various industrial fields, because of their high performances. However, previous studies mainly focused on low and medium temperatures; thus, curing behavior at high temperatures was less documented, which largely limits the deep understanding of epoxy resin formation and their applications in wider conditions. In this work, a novel curing agent, 4,4′-((methylenebis(4,1-phenylene))bis(azanediyl))bis(4-(furan-2-yl)butan-2-one) (AFPA), has been designed and synthesized via a one-pot method. The gelation time of epoxy system with AFPA underwater at 120 and 150 °C reaches 20 and 8 h, respectively. The activation energy of the system is calculated to be as high as 33.88 kJ mol–1, which accounts for the very long gelation time. Differential scanning calorimetry and thermogravimetric analysis results have shown that the glass-transition temperature of the epoxy resin is 123 °C, and the 5 wt % mass-loss temperature is 233 °C. Mechanical property tests have shown that the cured epoxy resin has good compressive strength, reaching 122 MPa at 30 °C and 41 MPa, even at 120 °C. A plugging experiment is designed and performed, and the results reveal that such epoxy system can easily pass through simulated formation rock fractures and cure in the presence of water at 120 °C to plug the fractures. We believe the findings in this work could provide an alternative way to develop systems with long curing times. Given the very long gelation time at high temperatures underwater and the good mechanical properties, such epoxy resin may find applications in water shut-off in the upstream of oil and gas industry, where water management underground is highly desired.