Influence of the Shell Material on the Properties of Epoxy Microcapsules for Self-Healing Applications

ROMINA OLLIER; MARCELA ELISABETH PENOFF; VERA ALVAREZ

Congreso; Frontiers in Polymer Science; 2015

Microcracking is a critical problem for polymers and polymer composites during their service in structural applications. The ability of self-healing materials to repair cracks is necessary to retain structural integrity. The route based on dispersing microcapsules filled with a healing agent which rupture upon a crack event, mimicking a biological ?bleeding?, seems to be very promising due to its versatility. One of the key features for the effectiveness of the healing system is the microcapsule design. The release properties depend on the healing agent properties, wall materials, the microencapsulation method, the physico-chemical parameters of the process, the mean particle size and the shell thickness. In order to have a successful self-healing performance, it is important to synthesize microcapsules with rough surface morphology to assure a good adhesion with de polymer matrix, low core material permeability, appropriate diameter and core content, and adequate shell thickness.Epoxy resins can react with a wide variety of curing agents at different temperatures. So they may be used as healing agents for the fabrication of self-healing composites. The microencapsulation of epoxy resins has increasingly attracted researchers? interest due to the fact that miscibility between the healing agent and the epoxy based composites is guaranteed. Moreover, high thermal decomposition temperature of epoxy resins may endow microcapsules with higher thermal stability. However, due to the fact that epoxy resins are adhesive materials, it is difficult to be uniformly emulsified and effectively encapsulated by in the in situ polymerization technique.The aim of this work was to synthesize poly (urea-formaldehyde) and poly(melamine-formaldehyde) walled microcapsules filled with epoxy monomers with different viscosities by in-situ polymerization. Several processing parameters affecting the final microcapsules? shape and size were carefully studied in the aim to obtain microcapsules with ideally spherical shape and uniform size. The microcapsules were morphologically, chemically and thermally analyzed