Synthesis of isocyanate microcapsules and micromechanical behavior improvement of microcapsule shells by oxygen plasma treated carbon nanotubes

Abstract

In this study, we present the novel isocyanate microcapsule preparation of poly(urea-formaldehyde) (PUF) embedded with oxygen plasma treated carbon nanotubes (OPCNTs) to improve the micromechanical behavior of microcapsule shells significantly. Isophorone diisocyanate was encapsulated by PUF through in situ polymerization. PUF, PUF with ultrasonically treated CNTs, and PUF with oxygen plasma treated CNTs (OPCNTs) microcapsules were characterized via field emission-scanning electron microscopy, 3D optical microscopy, fluorescence microscopy, laser diffraction analysis, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy and nanoindentation tests. As a result, OPCNTs modified by hydroxyl, carboxyl, and carbonyl groups, easily forming hydrogen bonds with water, could be highly dispersed in the shells of microcapsules during the thermosetting process. The particle size distributions of the microcapsules range from 10 to 200 μm with different reaction parameters. Although the CNT mass content of the OPCNTs microcapsules, as measured via TGA, is relatively small, the nanoindentation test indicated that the OPCNTs enhance the hardness and the Young's modulus of the microcapsule shells.