Stop the press! IBM Research announced this morning that it has discovered a whole new class of…plastics. This might not sound quite as sexy as, say, MIT discovering a whole new state of matter — but wait until you hear what these new plastics can do. This new class of plastics — or more accurately, polymers — are stronger than bone, have the ability to self-heal, are light-weight, and are 100% recyclable. The number of potential uses, spanning industries as disparate as aerospace and semiconductors, is dizzying. A new class of polymers hasn’t been discovered in over 20 years — and, in a rather novel twist, they weren’t discovered by chemists: they were discovered by IBM’s supercomputers.
One of the key components of modern industry and consumerism is the humble thermosetting plastic. Thermosetting plastics — which are just big lumps of gooey polymer that are shaped and then cured (baked) — are light and easy to work with, but incredibly hard and heat resistant. The problem is, once a thermoset has been cured, there’s no turning back — you can’t return it to its gooey state. This means that if you (the engineer, the designer) make a mistake, you have to start again. It also means that thermoset plastics cannot be recycled. Once you’re done with that Galaxy S5, the thermoset chassis can’t be melted down and reused; it goes straight to the dump. IBM’s new polymer retains all of a thermosetting plastic’s useful properties — but it can also be recycled.
IBM’s new class of polymers began life, as they often do in chemistry circles, as an accident. Jeannette Garcia had been working on another type of polymer, when she suddenly noticed that the solution in her flask had unexpectedly hardened. “We couldn’t get it out,” Garcia told Popular Mechanics. “We had to smash the flask with a hammer, and, even then, we couldn’t smash the material itself. It’s one of these serendipitous discoveries.” She didn’t know how she’d created this new polymer, though, and so she joined forces with IBM’s computational chemistry team to work backwards from the final polymer. Using IBM’s supercomputing might, the chemists and the techies were able to work back to mechanism that caused the surprise reaction.
Scanning electron microscope image of the new PHT polymer discovered by IBM Research
This new class of polymer is called polyhexahydrotriazine, or PHT. [DOI: 10.1126/science.1251484 - "Recyclable, Strong Thermosets and Organogels via Paraformaldehyde Condensation with Diamines"]. It’s formed from a reaction between paraformaldehyde and 4,4สน-oxydianiline (ODA), which are both already commonly used in polymer production (this is very important if they want the new polymer to be adopted by the industry). The end result shows very high strength and toughness, like other thermosets, but its heat resistance is a little lower than other thermosets (it decomposes at around 350C, rather than 425C).
An IBM Research infographic, for the new PHT polymer
Rather uniquely, though, IBM’s new polymer is both recyclable and self-healing. As you can see in the video above, chunks of the polymer readily rejoin to create a whole — and then when stretched in the future, they break randomly, not along the joins, proving a very high level of self-healing. [Read more about self-healing plastics.] Unlike traditional thermosets, which produce tons of recyclable waste every year, IBM’s PHT can be fully reverted back to its base state with sulfuric acid — which, as Garcia points out, is “essentially free.”
