Polyurethane-based microcapsules containing reactive isocyanate compounds: Study on preparation procedure and solvent replacement

In this study, preparation and characterization of isophorone diisocyanate (IPDI) filled polyurethane (PU) microcapsules were studied. At first, a pre-polymer was synthesized through reaction of toluene 2, 4- diisocyanate (TDI) with 1, 4- butanediol using either cyclohexanone or n-butyl acetate solvent. The synthesized pre-polymer was characterized using Fourier transform infrared spectroscopy, gel permeation chromatography, and free isocyanate content. Polyurethane-based microcapsules containing reactive isocyanates were synthesized using TDI-based pre-polymer and IPDI as the shell and core materials, respectively. Shape and morphology of prepared microcapsules were studied using optical microscopy and scanning electron microscopy (SEM). The spherical microcapsules prepared in this study had a diameter of 50-200 mu m and shell thickness of 2-20 mu m. The synthesis procedure developed in this work, replaces toxic solvents commonly used in the preparation of PU microcapsules, namely cyclohexanone and chlorobenzene, with a more benign solvent, namely n-butyl acetate. SEM microscopy of the scratched epoxy specimens showed appropriate healing performance using both type of microcapsules.