An efficient method for the output of new self-repairing materials through a reactive isocyanate encapsulation

An efficient method for the preparation of stable microcapsules with an industrially relevant core material was investigated for future use in self-repairing coatings. Microcapsules filled with isophorone diisocyanate (IPDI) were synthesized with different polymeric shells: polyurethane PU, poly(urea–formaldehyde) PUF and bi-layer polyurethane/poly(urea–formaldehyde) PU/PUF. Changing the encapsulation process by adding more shell wall monomers and pre-polymers allows the modulation of physical and mechanical properties of microcapsules. The thickness of microcapsules shell walls can be tuned for coating thicknesses and chemical environments. The effect of diverse process parameters and ingredients on the morphology of the microcapsules was observed by scanning electron microscopy (SEM) and optical microscopy (OM). Different techniques for the characterization of the chemical structure and the core content were considered such as Fourier transform infrared spectroscopy (FT-IR) as well as the characterization of thermal properties by differential scanning calorimetry (DSC). High yields of free flowing powder of spherical microcapsules were produced. The application of a liquid phase IPDI in self-healing polymer composite is studied. Diisocyanates, being reactive with water, introduce the possibility of achieving a really autonomous self-healing system in an aqueous or moisture-sensitive environment.