Examples of Applications

**79**

**Chapter 5**

**Abstract**

discussed.

Applications of Microcapsules in

Self-Healing Polymeric Materials

Self-healing polymeric materials have a great potential to be explored and utilized in many applications such as engineering and surface coating. Various smart materials with self-healing ability and unique self-healing mechanisms have been reported in recent publications. Currently, the most widely employed technique is by embedding microcapsules that contain a healing agent into the bulk polymer matrix. When cracks develop in the polymer matrix, the curing agent is released from the microcapsules to cross-link and repair the cracks. Microencapsulation of the healing agent in the core can be achieved by *in situ* polymerizing of shell material. This chapter presents a general review on self-healing materials, and particularly, self-healing of epoxy matrices that includes epoxy composite and epoxy coating by microencapsulation technique. Microencapsulation processes, including types of resin used, processing parameters such as core/shell ratio, concentration of emulsifiers, viscosities of aqueous and organic phases and stirring rate are

*Seng Neon Gan and Nurshafiza Shahabudin*

**Keywords:** self-healing, epoxy, microencapsulation, microcapsule

ing the cost of repair or replacement of failed component.

**1. Microcapsule-based self-healing epoxy composite and epoxy coating**

The use of microcapsule-based systems has attracted much attention during the last decade. The advantages include the esthetic recovery combined with the fast release of healing agent from the microcapsules [1]. This microcapsule-based approach could be easily integrated in many polymer systems, although the healing agent is locally depleted after a single damage event [2]. The attractive features of such technology include prolonging the service life-span of the materials and reduc-

Designing a microcapsule-based self-healing material requires a number of considerations. The first is to design the microcapsules, followed by incorporating them into the polymer matrices. Next, the viable mechanical characterization of the polymer during the occurrence of cracks should be studied. Finally, the extent of self-healing reactions must be determined and verified. Thus, the suitable encapsulation method for a particular healing agent must first be identified. One must consider the operation parameters such as solubility, reactivity, viscosity, and volatility of the healing agent. In the next step, the microcapsules should be integrated into the matrix host without being broken during mixing and must be well distributed. Microcapsules produced by encapsulating the healing agent in urea-formaldehyde (UF), melamine-formaldehyde/melamine-urea-formaldehyde (MF/MUF), and
