Engineering of polymer nanocomposites using acid-functionalized graphite nanoplatelets for high-temperature sealing purposes

This research aims to develop a novel nano-reinforcement strategy to produce polymer nanocomposites with enhanced thermal resistance for use in high-temperature geothermal well sealing. Improvement in surface characteristics of graphite nanoplatelets (GNPs) has been achieved through acid functionalization that introduces carboxyl (-COOH) groups to the surface. Polymer nanocomposites are then produced by incorporating varying contents of acid-functionalized GNPs, from 1.5 wt% through 9.0 wt%, into an ethylene propylene diene monomer (EPDM) matrix. This compounding process facilitates efficient dispersion of GNPs inside EPDM and ensures effective bonding between GNPs and the polymer matrix. The inclusion of 6.0 wt% GNPs is found to improve EPDM's storage modulus at high temperatures by more than 210 %, increase its loss modulus by over 156 %, and lower its tan δ by 17.34 %. Relative to EPDM without nano-reinforcement, the nanocomposites produced exhibit superior resistance to deformation via dissipating energy more efficiently, with the loss modulus's contribution to overall deformation resistance lowered. Heat necessary for melting the polymer (EPDM) is also significantly increased after the addition of modified GNPs, with the GNPs concentration 6.0 wt% demonstrating the most favorable result. Additionally, the polymer composite nano-reinforced with 6.0 wt% GNPs shows markedly better thermal stability relative to unreinforced EPDM. The proposed nano-reinforcement strategy can raise the long-term temperature resistance of EPDM by over 50 °C in a steam environment. As indicated by the above results, the nano-reinforced polymer proves a promising constituent material of geothermal well seals.