Thermoset can be reshaped and recycled

Heat-cured plastics called thermosets, which are used to make coatings and car parts, are strong and resilient. But they can’t be reshaped or recycled. Now, a malleable thermoset can be chopped up and reformed into an object that is just as strong as the original, and can be broken down into its starting material for reuse (J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b03257). Zhibin Guan of the University of California, Irvine, and coworkers used polymers containing boroxine, a six-membered ring of alternating boron and oxygen atoms synthesized by dehydrating boronic acid. They heated a solution of diboronic acid monomers for 12 hours, producing a stiff, strong boroxine-based thermoset insoluble in organic solvents. It could be reshaped when the researchers applied pressure and heat. The malleability derives from boroxine rings’ ability to break and reform in another part of the polymer network (shown) when they react with residual boronic acid groups.