Micro‐ and nanostructural characterization of melamine‐formaldehyde microcapsule shells using 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 microcapsules 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.