Robust
Composite-Shell Microcapsules via Pickering Emulsification
- Publication date
- Publisher
Abstract
Microencapsulation
technology has been increasingly applied toward the development of
self-healing paints. Added to paint as a dry powder prior to spraying,
the microcapsules store a liquid that can repair the protective barrier
layer if released into a scratch. However, self-healing will not occur
unless the microcapsules can withstand spray-painting, aggressive
solvents in the paint, and long-term exposure to the elements. We
have therefore developed a one-pot synthesis for the production of
Pickering microcapsules with outstanding strength, solvent resistance,
and barrier properties. Octadecyltrimethoxysilane-filled (OTS) microcapsules
form via standard interfacial polycondensation, except that silica
nanopowder (10–20 nm diameter) replaces the conventional surfactant
or hydrocolloid emulsifier. Isophorone diisocyanate (IPDI) in the
OTS core reacts with diethylenetriamine, polyethylenimine, and water
to form a hard polymer shell along the interface. Compared to pure
polyurea, the silica-polyurea composite improves the shelf life of
the OTS by 10 times. The addition of SiO<sub>2</sub> prevents leaching
of OTS into xylenes and hexanes for up to 80 days, and the resulting
microcapsules survive nebulization through a spray gun at 620 kPa
in a 500 cSt fluid