14 January, 2025
Effect of supercritical CO aging on the microstructure and mechanical properties of PEEK
Wael Badeghaish, Ahmed Wagih, X. Colin, H. Hoteit, Gilles Lubineau
Polymer Degradation and Stability (2025)
Polyetheretherketone (PEEK) is a promising material for oil and gas (O&G) downhole applications, having replaced metal parts owing to its excellent mechanical properties and corrosion resistance. In operations related to carbon capture and storage (CCS), CO-based geothermal systems, and enhanced oil recovery (EOR), carbon dioxide (CO) is injected into wells under conditions of high pressure and temperature, resulting in supercritical states (scCO). Herein, the effect of scCO on the microstructural and mechanical characteristics of PEEK was evaluated, particularly under conditions that simulated the extreme environments encountered in O&G downhole applications. Aging experiments were conducted on PEEK samples under scCO exposure at 150 °C and 100 bar in addition to gaseous CO, argon, and vacuum conditions to delineate the specific impacts of each agent. Thermal analysis via differential scanning calorimetry (DSC) unveiled a secondary crystal peak formation at 197 °C exclusively under scCO exposure, indicating significant microstructural changes with a 9% increase in crystallinity. Dynamic mechanical analysis (DMA) showed a notable increase of 6 °C in glass-transition temperature () under scCO exposure, suggesting enhanced thermal stability and reduced molecular mobility. In addition, mechanical tests revealed a 25% increase in yield strength, 8% increase in ultimate strength, and a considerable reduction in elongation at break due to enhanced crystallinity and limited amorphous phase mobility.