Wondrous polymer coating heals cracks, erases scratches

December 10th, 2008 - 1:40 pm ICT by IANS  

Washington, Dec 10 (IANS) A wondrous new coating will heal tiny cracks in your table or the scratch on your new car. They are designed to better protect materials from the effects of environmental exposure. Applications range from automotive paints and marine varnishes to the thick, rubbery coatings on patio furniture and park benches.

“Starting from our earlier work on self-healing materials at University of Illinois (Urbana-Champaign), we have now created self-healing coatings that automatically repair themselves and prevent corrosion of the underlying substrate,” said Paul Braun, professor of materials science and engineering and co-author of the study.

To make self-repairing coatings, the researchers first encapsulate a catalyst into spheres less than 100 microns in diameter (a micron is a millionth of a metre).

They also encapsulate a healing agent into similarly sized microcapsules. The microcapsules are then dispersed within the desired coating material and applied to the substrate, said an Illinois release.

“By encapsulating both the catalyst and the healing agent, we have created a dual capsule system that can be added to virtually any liquid coating material,” said Braun.

When the coating is scratched, some of the capsules break open, spilling their contents into the damaged region. The catalyst and healing agent react, repairing the damage within minutes or hours, depending upon environmental conditions.

The performance of the self-healing coating system was evaluated through corrosion testing of damaged and healed coated steel samples compared to control samples that contained no healing agents in the coating.

Reproducible damage was induced by scratching through the 100-micron-thick polymer coating and into the steel substrate using a razor blade. The samples were then immersed in a salt solution and compared over time.

The control samples corroded within 24 hours and exhibited extensive rust formation, most prevalently within the groove of the scratched regions, but also extending across the substrate surface, the researchers report.

In dramatic contrast, the self-healing samples showed no visual evidence of corrosion even after 120 hours of exposure.

These findings will be published in Advanced Materials and posted on its website.

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