James E. Kloeppel,
Physical Sciences Editor
— A new catalyst-free, self-healing material system developed
by researchers at the University of Illinois offers a far less expensive and far
more practical way to repair composite materials used in structural applications
ranging from airplane fuselages to wind-farm propeller blades.
The new self-healing system incorporates chlorobenzene microcapsules, as small as 150 microns in diameter, as an active solvent. The expensive, ruthenium-based Grubbs’ catalyst, which was required in the researchers’ first approach, is no longer needed.
“By removing the catalyst from our material system, we now have a simpler and more economical alternative for strength recovery after crack damage has occurred,” said Jeffrey Moore, the Murchison-Mallory Professor of Chemistry at Illinois. “Self-healing of epoxy materials with encapsulated solvents can prevent further crack propagation, while recovering most of the material’s mechanical integrity.”
The new chemistry is described in a paper accepted for publication in Macromolecules, and posted on the journal’s Web site.
During normal use, epoxy-based materials experience stresses that can cause cracking, which can lead to mechanical failure. Autonomous self-healing – a process in which the damage itself triggers the repair mechanism – can retain structural integrity and extend the lifetime of the material.
“Although we demonstrated the self-healing concept with a ruthenium-based catalyst, the cost of the catalyst made our original approach too expensive and impractical,” said Moore, who also is affiliated with the university’s Frederick Seitz Materials Research Laboratory and with the Beckman Institute. “Our new self-healing system is simple, very economical and potentially robust.”