Synthesis, Characterizations and Mechanical Properties of Microcapsules with Dual Shell of Polyurethane (PU)/Melamine Formaldehyde (MF): Effect of Different Chain Extenders

The mechanical properties and microstructure of moisture-curing polyurethane (PU)/melamine formaldehyde (MF) microcapsules are not clear yet because of the complicated oil/water formulation process. PU/MF microcapsules with isophorone diisocyanate as core were formulated with butanediol (BDO), polyethylene glycol (PEG) 400, PEG 1000, and PEG 2000 using a two-step synthesis method in this work. The resulted microcapsules were characterized using various techniques. Furthermore, their mechanical properties were measured using a micromanipulation technique, showing that PU/MF microcapsules were successfully synthesized with the different alcohol chain extenders and the main groups have been revealed by their FTIR spectra. The morphologies of the microcapsules displayed the differences caused by the chain extenders. Size distributions and mechanical properties were measured to study the effects of the length of alcohol chain extenders. TEM imagines with sharp interfaces between PU and MF layers and data of SEM-EDS of the shell identified the mechanism of reactions in the shell.