A new type of plastic can rapidly heal itself under water, even in harsh conditions. It maintains its strength after self-healing, so it may be useful in emergencies at sea.
at Tsinghua University in China and her colleagues developed this material, called Rapid Underwater Self-healing Stiff Elastomer (RUSSE) because most self-healing polymers don鈥檛 work very well under water. 鈥淩oom temperature self-healing polymers generally have a poor underwater stability, low healing strength and a slow healing process,鈥� says Chen.
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RUSSE is made of small chunks of a type of soft polymer used in some paints connected by nanometre-sized chains of a tougher polymer. The researchers tested the material鈥檚 properties by stretching it, cutting it and bashing it with a hammer.
They found that it could be stretched by 1400 per cent without breaking, bear 1000 times its own weight without changing shape and heal itself in only 10 seconds when cut up and then pressed back together by hand. This is because the molecules that make up one of the polymers have one negatively charged and one positively charged end, which attract and knit the material back together. After the first 10 seconds, the material continued to slowly regain its structural strength as more of the molecules linked up, returning to nearly its original toughness in just 5 minutes.
When the researchers tested RUSSE in salty water, its elasticity and self-healing abilities were only slightly impaired, with cut samples healing to 80 per cent toughness in 5 minutes. The results of tests in acidic and basic solutions were similar, and a sample left in salt water for a month retained its initial properties.
This material could be useful for repairing underwater equipment in the case of emergencies, says Chen. For example, if a diver鈥檚 air tank tubes unexpectedly break and there is an interruption in the gas flow, they could die in seconds, she says. 鈥淪uch stiff and fast-healing materials can play an important role in these dangerous and urgent cases.鈥� RUSSE could even be used as a coating in underwater pipes to make them easier and quicker to repair, she says.
Advanced Functional Materials
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