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Self-healing polymers - an introduction

Jinglei Yang's picture

I'm now working on the preparation and characterization of self-healing polymers, a promising branch in materials science. The following is a general conception of this kind of materials system. (Pasted from our group website http://www.autonomic.uiuc.edu.) I may introduce some of my current work later.

Structural polymers are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. Cracking leads to mechanical degradation of fiber-reinforced polymer composites; in microelectronic polymeric components it can also lead to electrical failure. Microcracking induced by thermal and mechanical fatigue is also a long-standing problem in polymer adhesives. Regardless of the application, once cracks have formed within polymeric materials, the integrity of the structure is significantly compromised. We have developed a structural polymeric material with the ability to autonomically heal cracks.

Engineering this self-healing composite involves the challenge of combining polymer science, experimental and analytical mechanics, and composites processing principles. Autonomic healing is accomplished by incorporating a microencapsulated healing agent and a catalytic chemical trigger within an epoxy matrix. An approaching crack ruptures embedded microcapsules, releasing healing agent into the crack plane through capillary action.

Polymerization of the healing agent is triggered by contact with the embedded catalyst, bonding the crack faces. The damage-induced triggering mechanism provides site-specific autonomic control of repair. An additional unique feature of our healing concept is the utilization of living polymerization (that is, having unterminated chain-ends) catalysts, thus enabling multiple healing events. Our fracture experiments yield more than 90% recovery in toughness, and we expect that our approach will be applicable to other brittle materials systems (including ceramics and glasses).

 

BTW, two nature papers since 2001 from AMS Group at UIUC can be found here: http://www.nature.com/nature/journal/v409/n6822/full/409794a0.html
http://www.nature.com/nature/journal/v446/n7134/full/nature05681.html

Comments

You have rightfully explain the benefits of this new introduction "self healing polymers". I definately agree with your comments. But I just want to add that I have readsimilar article in the tech. section of  www.webdesigningcompany.net

You should better visit there to get more on the subject.It will be certainly be very helpful. 

 

Henry Tan's picture

Jinglei, 

Does the self-healing take a long time?

Jinglei Yang's picture

Henry,

That's a good question. We are now taking 24 hours for trying to get a complete polymerization reaction and an enough gel time. Actually, this healing time can be reduced to 10 hours. We are also attempting to find out optimized catalysts and suitable healing agents for even shorter healing time within a couple of hours or one hour.

Jinglei 

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