CONICET | Buscador de Institutos y Recursos Humanos

Advances in the study of composite polymeric materials for structural applications have suggested the possibility of an early elimination of cracks to avoid macroscopic damage of the material. Hence, the concept of self-healing composite materials has been introduced to reduce the maintenance cost and frequency, to increase the life in service and to expand the applications of these materials. One of the most successful and versatile approach consists on embedding an encapsulated healing agent inside the matrix. One of the key features for the effectiveness of this healing system is the microcapsule design. 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. The aim of this work was to synthesize poly (urea-formaldehyde) (PUF) and poly(melamine-formaldehyde) (PMF) microcapsules filled with an epoxy monomer. Microcapsules were prepared by in situ polymerization in oil-in-water emulsion and several reaction conditions were analyzed, by changing the following parameters: the rate of agitation, the concentration of surfactant and the viscosity of the encapsulated phase. The effect of the addition of nanoclay along the shell was also studied. The final step of filtering and washing the obtained capsules with different solvents was analyzed as well. The microcapsules were morphologically and thermally analyzed. PUF capsules were partially collapsed and presented a limited thermal stability, whereas PMF capsules had spherical and regular shapes with an enhanced thermal stability.