Influence of the Characterization Methodology on the Repair Performance of Self-Healing Materials

Covalent Adaptable Network (CAN) chemistry has been extensively introduced in thermoset resins in order to achieve self-healing properties. These vitrimeric polymers are composed of dynamic covalent bonds that break and re-form reversibly when subjected to an external stimulus, such as an increase of the temperature, pH variations, or UV induction. Among the different self-healing mechanisms, aromatic disulfide bridges have attracted much attention on recent works. These CANs are based on exchange reactions between adjacent S–S bonds that trigger a decrease of the viscosity that permits the polymer gain a high molecular mobility state and flow to recover from distortions, being able to restore the original properties of the material, i.e, self-healing.

Although repair phenomena have been demonstrated in previous investigations by healing cracks from a scratched surface, this kind of damage leads to material loss. Consequently, the restored material volume may not be the same as the original, so that the self-healing performance is expected to be degraded.

In this regard, this research is focused on the study of the effect of the characterization methodology on the repair performance of self-healing materials. In this work, disulfide bonds were incorporated into an epoxy monomer with 2-Aminophenyl disulfide (AFD). The surface of the specimens was cut to generate cracks of different controlled depths. The self-healing efficiency was calculated from the relation between the volume of the damaged zone prior and after being repaired via thermal convective stimulus. The creep volumes were calculated and characterized from the images obtained with an optical profilometer. In addition, a comparative analysis between the volumes obtained via the optical profilometer and a Field Emission Gun – Scanning Electron Microscope (FEG-SEM) is included in order to ensure that acceptable measurement tolerances were accomplished.