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Low-Cost Polymer Heals without Help

Thursday, February 20, 2014

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A simple new polymer made from off-the-shelf materials can knit itself back together repeatedly, without a catalyst, even at low temperatures, University of Illinois researchers report.

The new product appears to advance the development of self-healing material technology by several major steps, with implications for a wide range of materials.

What looks like tiny dogbone-shaped gummies now could be the beginning of peel-off coatings and self-healing plastics, according to materials science and engineering professor Jianjun Cheng, graduate student Hanze Ying, and postdoctoral researcher Yanfeng Zhang.

Self-Healing Polymer Self-Healing Polymer
Photos, video: University of Illinois / Anne Lukeman

The plastic polymer was cut in two and allowed to heal overnight. Stretching the polymer did not break it.

Their paper, “Dynamic Urea Bond for the Design of Reversible and Self-Healing Polymers,” was recently published in the journal Nature Communications.

'Anybody Can Do This'

"We just buy commercial materials and mix them together, no fancy controls or special apparatus," said Cheng. "It's a very simple, low-cost, inexpensive process. Anybody can do this on any scale."

He adds: "The key advantage of using this material is that it's catalyst-free and low-temperature, and can be healed multiple times.

"These are very nice materials for internal cracks. This can heal the crack before it causes major problems by propagating."

Elastic polymers heal at the molecular level after they are cut in this University of Illinois demonstration.

Unlike other self-healing materials, the new product uses softer elastic materials made out of polyurea, one of the most common classes of polymers used in paints, coatings, elastics, plastics, and other consumer goods, the university reports.

Dynamic Chemistry

The polymer is made with commercially available ingredients. By tweaking the structure of the polymer's molecules, the team "can make the bonds between the molecules longer so that they can more easily pull apart and stick back together—the key for healing," the university says.

This molecular-level re-bonding, called dynamic chemistry, uses consumer materials and readily available ingredients, the team says.

When the polymer is cut or torn, the researchers press the two pieces back together and let the sample sit for about a day to heal. No chemicals or catalysts are required.

Furthermore, the team says, the materials can heal at room temperature, although curing at slightly higher temperatures (37 degrees Celsius, or about body temperature) does speed up the process.

HanzeYing

Graduate student Hanze Ying and colleagues at the University of Illinois developed the low-cost material, which requires no catalyst to self-heal.

The team says the mended polymer bonds "nearly as strongly as before it was cut."

In fact, the team adds, some healed samples tore in a new place when stretched, while the repaired area held.

What it Might Do

The researchers hope manufacturers can easily integrate the dynamic materials and are exploring how the polyurea could perform in different applications.

One possibility, they say, is a removable polyurethane coating or paint.

“In some areas, when it’s not necessary for the coating to be permanent and you want it to be removable, this chemistry may be applied to existing coating materials to make it reversible,” Cheng said.

“In general, polyurea and polyurethane are widely used. This chemistry could modify existing materials to make them more dynamic, healable.”

The research is supported by the National Science Foundation and the National Institutes of Health.

   

Tagged categories: Marine Coatings; Polymers; Polyurea; Polyurethane; Research; Self-healing

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