Optimization of a microfluidic process to encapsulate isocyanate for autoreactive and ecological adhesives

The present paper reports a continuous microfluidic approach for the preparation of microcapsules (MCs), by interfacial polymerization, with a polyurea/polyurethane (PUa/PU) shell containing isophorone diisocyanate (IPDI). The microfluidic system enables the formation of a monodisperse oil-in-water (O/W) emulsion by a separate flow of the reagents along the tubing system, which posteriorly meet at a cross-junction, resulting in the precise formation of one emulsion droplet at a time. The developed MCs are intended to be part of a new monocomponent, autoreactive and ecological adhesive, as cross-linking agents. Critical operational parameters in the microfluidic process were investigated, namely the flow rate of the emulsion phases, the cross-junction’s configuration and its correlation with the MCs’ morphology, average diameter, size distribution and amount of encapsulated isocyanate. The advances achieved in the current study represent a contribution to the development of new sustainable and eco-friendly products, where the employment of monodisperse MCs is an advantage.