Researchers make self-healing plastic from common, safe materials
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Harrowing moments spent hovering over a broken bit of plastic with a tube of superglue may not be a part of your future if some new research from University of Illinois pans out. Materials science professor Jianjun Cheng and his team have used a modification in the chemical structure of a common plastic to make a material that can not only heal cracks, it can put itself back together after being cut or torn apart.
This new substance is a tweak on polyurea, which is widely used in spandex, pipe linings, paint containers, and more. It is a softer, more flexible plastic than some other targets of self-healing materials research. However, these properties also make it much better at knitting itself back together.
No catalysts are required for this super-polyurea to start fixing itself — it can even take place at room temperature. Researchers have found that a piece of the plastic that has been cut in two can be repaired in less than a day. All one has to do is press the two bits together and leave them alone overnight. The process can be accelerated heating the polyurea to about 37 degrees, which is conveniently close to human body temperature.
The key to designing this material was making the bonds between the individual molecules within the polymer longer. This gives the material a bit more elasticity and also allows the ends of polymers to more easily recombine after then have been separated. Samples tested by the team showed remarkable levels of healing after being cut. Even when stretched to their limits, samples often failed at completely different points rather than the original site of damage. This indicates the re-polymerization of the polyurea could even be enhancing the strength of the material when it is healed — a bit like the toughened skin of scar tissue.
Polyurea created with this process would also resists wear and tear. It heals itself from any damage, so small cracks and cuts could repair themselves over time to prevent larger issues from forming. A paint based on polyurea could also fill in small chips and cracks to look new for longer. (Research paper: doi:10.1038/ncomms4218 – “Dynamic urea bond for the design of reversible and self-healing polymers”).
The process for making this tweaked polymer doesn’t rely on any crazy equipment or dangerous reagents — it’s all based on commercially available ingredients that are generally regarded as safe. The polymer is mixed in a liquid state, then is cured in a mold to solidify. The ease of production means this substance (which is still experimental) could end up in consumer products sooner than most new materials.