Optimisation of microencapsulation of isophorone diisocyanate into polyurea shell by oil-in-water interfacial polymerisation

In this work, microcapsules containing isophorone diisocyanate (IPDI) encapsulated within a polyurea (PU) shell were synthesised via an oil-in-water emulsion interfacial polymerisation reaction involving tris(4-isocyanato phenyl)thiophosphate (TIPTP) and triethylenetetramine (TETA). Characterisation of the resulting microcapsules was conducted using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), optical microscopy and scanning electron microscopy (SEM). Various encapsulation parameters such as core-to-shell ratio, agitation speed, emulsifier type and concentration, and reaction time were systematically varied at four different levels. Optimisation of microencapsulation was performed using a Taguchi L16 parameter design approach, aiming to maximise desired outcomes (i.e. maximal core content and yield) while keeping the targeted microcapsule diameter of 50 µm. Under optimal conditions, the IPDI core content within microcapsules was up to 75% and the microcapsule yield was up to 49%.