Microencapsulation of various reactive monomers by in situ polymerization

ROMINA OLLIER; ELISABETH PENOFF; EXEQUIEL RODRIGUEZ; VERA ALVAREZ

Gante

Congreso; International Conference on Self Healing Materials (ICSHM2013); 2013

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 haling agent inside the matrix. 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. The aim of this work was to synthesize poly(urea-formaldehyde) microcapsules filled with different reactive monomers: dicyclopentadiene and two epoxy monomers. Microcapsules were prepared by in situ polymerization in oil-in-water emulsion and the best experimental conditions were selected to optimize the subsequent healing efficiency. Many reaction conditions were analyzed: the rate of agitation, the concentration of surfactant and the viscosity of the encapsulated phase. As the commercial epoxy resins have high viscosity, they may not be used directly as healing agents, so the addition of reactive diluents to the sequestrated phase was evaluated as well. The improvement of the barrier property by the addition of nanodispersed clay along the shell was also studied. The final step of filtering and washing the obtained capsules with different solvents was analyzed showing interesting results.