Poly(urea-formaldehyde) microcapsules - synthesis and influence of stirring speed on capsules size

Microcapsules from commercially available epoxy resin (Epidian (R) 52) and an organic solvent (ethyl phenylacetate, EPA), for application to self-healing epoxides, were prepared. Poly(urea-formaldehyde) microcapsules containing the active ingredients were prepared using in situ polymerization in an oil-in-water emulsion. The prepared capsules were characterized by scanning electron microscope (SEM) for their surface morphology and size distribution. Thermogravimetric analysis (TGA) has been carried out to determine their thermal stability and maximum processing temperature. Moreover, the influence of stirring speed on their size distribution was investigated in predefined conditions. It is demonstrated that microcapsules can be easily prepared using the literature methodology and that the urea-formaldehyde polymer is a good barrier for the enclosed epoxy resin-organic solvent. Performed experiments suggest that size of microcapsules can be controlled by the stirring speed of the emulsion and that the capsules are thermally stable up to 140 degrees C for 24 hours. Additional studies showed that microcapsules exhibit excellent interface with a commercial epoxy resin matrix cured at elevated temperatures what is desired in their further application.