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Self-healing polymer fixes its own crack self healing protective plastics coating

Self-healing polymer fixes its own crack self healing protective plastics coating

Plastics are made up of polymers, a long chain of molecules that are connected through chemical bonds. As much as synthetic polymers mimic natural polymers, they've always lacked one important feature, the ability to heal themselves-until now. Nicknamed “Terminator,” a new material has been developed by researchers from the Center for Electrochemical Technologies in San Sebastian, Spain. The self-healing polymer could be used to bolster the integrity and lifetime of plastic parts in common products. The Spanish scientists recently created a polymer that can bind itself back together even after being sliced with a razor blade, without the help of a catalyst. This is the first man-made self-healing polymer to function without a catalyst. First, a pristine cylinder made from [the polymer] was cut in half with a knife. Then the two halves were put in contact and allowed to stand at room-temperature, without applying any pressure. "Terminator" started self-healing within an hour. It was 97% healed within 2 hours, and completely fused after 22 hours. Once it had repaired itself, the scientists were able to stretch it manually, with no ruptures or tears. In this study, the polymer is a type of thermoset elastometer. The scientists created it using common polymeric starter materials, just as they would in order to create other known synthetic polymers. The idea behind this is to reconnect the chemical cross links which are broken when a material fractures, restoring the integrity of the material. This is expected to provide polymers with enhanced lifetime and resistance to fatigue. When the polymer was at room temperature, bis(4-aminophenyl) disulfides were exchanged between the two slices of the polymer through metathesis. The exchange facilitated the regeneration. The fact that poly(urea-urethane)s with similar chemical composition and mechanical properties are already used in a wide range of commercial products makes this system very attractive for a fast and easy implementation in real industrial applications. The group’s main goal now is to make a harder version, perhaps one that could be formed into such parts itself. As it exists today, the polymer is squishy and somewhat soft. The researchers couldn’t stretch a single piece to breaking by hand, either before or after the cut, but it’s not rigid enough to make parts from just yet.

Inventors have long been in search of a self-healing protective coating, a top-sheet that could soak up small nicks and return to its prior state. Dutch researchers from the Eindhoven University of Technology have created a non-stick protective plastic coating that heals itself when scratched. While coatings with highly water-resistant or antibacterial properties are nothing new, their applications have been limited as they can easily lose these properties. This is because the nano-sized molecular groups that provide these properties are easily and irreversibly damaged by minor contact with the surface on which they are applied. The research team claim to have solved this problem with the development of surfaces that place the functional chemical groups at the end of special “stalks” that are mixed through the coating. When the outer surface layer is removed by scratching, the “stalks” in the layer underneath re-orient themselves to the new surface to restore their function. The researchers say this will enable the creation of highly water-resistant coatings that could be applied to cars so that superficial scratches heal themselves and water droplets roll off the car, taking dirt with them. The technology could also be used in self-healing mobile phone displays, solar panels and contact lenses. The researchers say that aircraft using the self-cleaning technology would benefit from reduced fuel consumption due to the cleaner surface providing less air resistance, while ships could employ it to prevent the build-up of algae on their hulls. It would also reduce the frequency with which aircraft and ships need repainting. The researchers point out that the technology only works with superficial scratches that don’t completely penetrate the coating. The team plan to collaborate with other universities and industrial partners to develop the technology further, with the first coatings likely to be ready for production within six to eight years. The team expects the prices to be comparable to coatings currently on the market. Self-healing coatings could replace screen protectors on smart phones and tablets, and possibly provide better protection against dirt and fingerprint smudges.

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