New Approach for the Synthesis of Nanozirconia Fortified Microcapsules

Robust poly(urea-formaldehyde) (PUF) microcapsules with composite shells comprising zirconia (ZrO₂) nanopowder incorporated in PUF were fabricated via a novel and facile one-pot synthesis. ZrO₂ nanopowder was chosen because it owns one of the highest mechanical strengths among ceramics. The nanopowder was predispersed in the core material to combine encapsulation and fortification into a single process. In the core, the well-dispersed nanopowder migrated to the interface, where PUF polymerization took place. The mechanical strength of the microcapsule with nano-ZrO₂ incorporated in the shell (42% by weight) is three times greater than that of the microcapsule without ZrO₂. In a preliminary application wherein the microcapsules were embedded in a model of poly(vinyl alcohol) (PVA) membrane, the PVA specimen exhibited a higher ultimate tensile strength when fortified microcapsules were embedded than when unfortified microcapsules were used.