Microencapsulation of self-healing agents with melamine-urea-formaldehyde by the Shirasu porous glass (SPG) emulsification technique

Abstract

Norbornene-based healing agent candidates, 5-ethylidene-2-norbornene (ENB) and ENB with a custom crosslinker, were prepared into uniform microspheres using a Shirasu porous glass (SPG) emulsification technique, and microencapsulated by in situ polymerization of melamine-urea-formaldehyde (MUF). The resulting microcapsules were observed by optical and scanning electron microscopy for their morphology, outer and inner surface and shell thickness. Particle size analysis revealed a more uniform size distribution with a mean diameter of 40 mu m than a conventional method using a mechanical impeller. The thermal and mechanical properties of the microcapsules were also examined by considering fabrication of self-healing composites.