Many of the polymers that make up the items we rely on are relatively easy to break down. An otherwise robust styrofoam container will dissolve completely in a solvent like chloroform. Thermoplastics like the ones found in food delivery containers get soft at higher temperatures. Raise the heat a bit more, and they’ll melt. These properties help make many of the plastics we use recyclable.
But there are other plastics, called thermosets, that don’t show this kind of behavior. They are extremely durable, they will shrug off solvents, and they will hold up well to heat, which makes them great for the places you’ve probably come across them—things like auto interiors and cases for electronic devices. The problem is that the same properties that make them so robust also make them nearly impossible to recycle.
Now, materials scientists have come up with a new thermoset polymer that’s quite tough and holds up to high temperatures and most solvents. Its Achilles’ heel? Strong acids. Put it in a solution with a pH below 2, and it will break back down into its component molecules, which can then be reused to form the same polymer all over again.