Melamine -formaldehyde microcapsules: micro - and nanostructural characterization with electron microscopy

Abstract

A systematic study has been carried out to compare the surface morphology, shell thickness, mechanical properties and binding behavior of melamine formaldehyde icrocapsules of 5 to 30 µm diameter size with various amounts of core content by using scanning and transmission electron microscopy including electron tomography, in-situ nanomechanical tensile testing and electron energy-loss spectroscopy. It is found that porosities are present at the outside surface of the capsule shell but not at the inner surface of the shell. Nano-mechanical tensile tests on the capsule shells reveal that the Young?s modulus of the shell material is higher than that of bulk melamine formaldehyde and that the shells exhibit a larger fracture strain compared to the bulk. Core-loss elemental analysis of microcapsules embedded in epoxy indicates that during the curing process, the microcapsule-matrix interface remains uniform and the epoxy matrix penetrates into the surface microporosities of the capsule shells.