ABSTRACT
The healing materials are entrapped in the microcapsules as a storage material and possess the capability to polymerize after the breakdown of the capsules. In capsule-based self-healing, capsules containing the active healing agent are uniformly dispersed in a variety of coating formulations, and at the time of scratching, healing is triggered over the damaged surface by curing of the healing agent that is released from the broken microcapsules. A mono-capsule-based system consists of polymeric microcapsules with only healing agent, which does not require any catalyst or hardener for curing or repair. The shell of a microcapsule is an outer layer used to protect the inner core material from atmospheric conditions. The selection of the shell is crucial in the preparation of microcapsules, as it decides most of the properties of capsules, that is, thermal stability, release behavior, protection of the core, and stability against several environmental factors.
