Biobased ESO–epoxy semi-liquid gels for industrial sealing: Injectability–adhesion balance and γ-valerolactone enabled degradation

Epoxidized soybean oil (ESO) offers a renewable, multifunctional modifier for developing sustainable epoxy-based sealing systems, yet its role in balancing injectability, mechanical performance, and removability under wellbore conditions remains insufficiently clarified. In this work, a semi-liquid gel was prepared from E51 epoxy resin and methylhexahydrophthalic anhydride, incorporating ESO as a biobased reactive component, n-butyl glycidyl ether as a diluent, and octadecyltrichlorosilane (OTS) as an interfacial enhancer. The precursor exhibited low initial viscosity (<100 mPa·s at 25 °C) and tunable gelation times of 1–10 h at 120–140 °C, ensuring smooth injection and in situ curing. The cured gels achieved compressive strengths above 100 MPa, with ESO contributing flexible ester linkages that improved toughness. OTS addition significantly reinforced interfacial adhesion, with the 0.25 wt% OTS-containing formulation showing an over fourfold increase in adhesion strength and producing an interfacial layer nearly 400 nm thick within the investigated range. Plugging tests in sand-packed tubes demonstrated nonlinear scaling of breakthrough resistance with injected volume and bonded area, highlighting reliable sealing under both steady and cyclic gas loads. Importantly, the network underwent complete liquefaction within 48 h at 120 °C when exposed to a γ-valerolactone/p-toluenesulfonic acid medium, reflecting an acid-catalyzed solvolysis mechanism and enabling practical removal. These results establish a biobased ESO–epoxy system that integrates injectability, strength, interfacial reliability, and green degradability, providing a sustainable pathway for industrial wellbore sealing applications.