DYNAMIC REVERSIBLE NETWORKS AND DEVELOPMENT OF SELF-HEALING RUBBERS: A CRITICAL REVIEW

ABSTRACT An intensive literature search shows that research in the field of self-healing rubbers is still in its infancy. By analyzing the various reviews and reports available, most of the results prove to be complicated; however, a few studies show promising self-healing properties of new elastomers. Most of these materials were prepared by relatively sophisticated chemical syntheses. Many of the studies on self-healing materials also deal with commercial rubbers, but the mechanical performance of these self-healing systems is very poor for practical application, perhaps because self-healing systems are usually prepared with an uncured or pseudo-crosslinked matrix structure. The poor mechanical properties are related to the highly viscous but inelastic nature of the uncured or only partially cured rubber compound. Importantly, most of the studies have been conducted on rubber systems without reinforcing fillers. For filler-reinforced rubber systems, the question is whether the working principle of reversible bonds is applicable. This literature review attempted to compile the current promising self-healing systems, describe their underlying chemical mechanisms, and discuss the self-healing concept from a thermodynamic perspective. In addition, this review is focused on the critical discussion of the principle and origin of self-healing behavior and finally draws conclusions on the applications and opportunities for further developments in this field.