A New Sustainable Self-Healing System; Autonomous Repair for Glass Reinforced Epoxy Liner for Water Injector Tubing

Abstract Often in the water injector (WI) system with liners, the "unseen" damage such as micro scratch is very difficult to be detected, and these micro scratches, when not detected will eventually become a major damage. Employing self-healing technology in the liner will ensure that the minor damage will be healed autonomously during operation, subsequently preventing further major damage. The in-situ healing of the damages is one of the amazing criteria offered by this technology. The integrity of the WI system is eventually assured, prolonging the service life of the materials and avoiding unnecessary expensive inspection and maintenance. In this present work, self-healing technology has been developed for the epoxy-based materials used in glass-reinforced (GRE) liner system for WI tubing. The novel self-healing additives were synthesized using a facile synthesis method and have been proven to be able to potentially replace the expensive rare-earth based catalyst, hence making the commercial step viable. The metal-organic frameworks (MOFs) microcapsules self-healing in the epoxy-based liner system demonstrated successful autonomous healing efficiency at elevated temperatures as examined using a 3D-profilometer, with a healing efficiency of more than 80%. The system with the self-healing additives was able to recover the barrier performance of the liner, up to 98% efficiency as shown by the electrochemical impedance spectroscopy (EIS) assessment. In addition to that, within 2 hours of healing activation by temperature, the samples with the self-healing additives were able to autonomously heal, reaching more than 50% healing efficiency. Moreover, this self-healing system was able to heal a damage width of up to 700µm, for more than 80% healing efficiency. It is worth mentioning that the healing ability remained functional even though the samples had been exposed to harsh conditions for 1000 hours. The healing agent particularly contained in the microcapsules remains intact and stable throughout the stability study, hence suggesting a robust self-healing system. This finding shows the possibility of this technology to provide a sustainable production of self-healing additives for a liner in water injector's well, hence potentially improving the integrity of the materials.