Cracking up

 作者:国模匪     |      日期:2019-03-07 05:07:03
By Ian Sample Cracks in structures tend to be bad news. But a team of US scientists have developed a material that heals its own cracks as they appear. “The applications are enormous if we can achieve all our technical goals within a reasonable cost,” says Scott White whose team developed the material at the University of Illinois at Urbana-Champaign. To make a “self-healing” polymer, White mixed the catalyst and microspheres into an epoxy polymer. The result was a solid polymer with microspheres and particles of catalyst dispersed evenly inside it. White found that when a crack formed in the epoxy, it broke open the brittle microspheres, releasing the DCPT. This flooded into the crack, came into contact with the particles of catalyst and polymerised, sealing up the crack. In tests, the self-healing material was found to be significantly tougher than the original epoxy. White says the technology could be used to toughen common devices like mobile phones. The keypads, he says, often break because fatigue fractures appear in the circuit boards of phones. These then break electrical connections. “Their failure is primarily due to small microcracks that open up and eventually propagate and lead to either mechanical fracture or electrical failure,” he says. “If we can incorporate an autonomic healing polymer into the electronic circuit board, we can delay or prevent this failure from occurring.” The technology could be used for more critical applications as well, adds White. “Aerospace companies are also interested in the technology to heal cracks in-flight.” “It’s a neatish idea and you can see the advantages,” says Tony Kinloch, of the Strength of Materials group at London’s Imperial College. But Kinloch says the technique would not protect fragile circuits from cracks because it fills the cracks rather than closing them back up. “This stuff won’t stop microcracking, it’ll just repair it,” he says. White says this could be just the first step in self-healing materials. Future materials could incorporate circulatory systems that continually transport chemicals and building blocks for healing to sites of damage in the material, he says. More at:: Nature (vol 409,