Upcycling of waste ABS into 3D-printable material with enhanced properties

In an advancement toward circularity for commodity plastics, researchers at the Oak Ridge National Laboratory (ORNL; Oak Ridge, Tenn.; www.ornl.gov) have developed a method for upcycling the commodity thermoplastic acrylonitrile butadiene styrene (ABS) into an ABS-vitrimer material that can be used in fused-filament fabrication (FFF), a popular 3D-printing technique. When used in 3D printing, the resulting material produces stronger, tougher and more solvent-resistant three-dimensional components (photo) that are themselves easily recyclable.

“We need fundamental discoveries to overcome the challenges of increased costs and deteriorating material properties associated with recycling,” says Tomonori Saito, ORNL researcher and corresponding author on the study. “Our goal was to develop an easily adoptable strategy that reuses plastic waste to create a more valuable material instead of generating fresh plastic.”

ABS is used in a wide range of end-use products, including automobile components, table-tennis balls, and LEGO blocks. Led by Saito, the ORNL team generated ABS-vitrimers by implementing thiol-ene “click” chemistry to functionalize butadiene segments with cysteamine, followed by reacting with a short-chain dialdehyde (glutaraldehyde) to produce ABS-vitrimer.

Vitrimers feature networks of dynamic covalent bonds that can undergo thermally activated bond-exchange reactions. They exhibit mechanical robustness and chemical resistance because of their covalent network formation, but vitrimers can also be malleable by reconfiguring reversible cross-links through the associative bond exchange at elevated temperature, making it recyclable, the ORNL team says.

The ABS-vitrimers also have added solvent resistance, which enables their easy separation from mixed, unsorted plastic waste commonly encountered in recycling scenarios. The team dissolved mixed plastic waste in various solvents, and in each experiment, upcycled ABS maintained its structure, while all other plastics, including ABS, completely dissolved.

The researchers expect that the value-enhancing recycling process for the ABS-vitrimers will also reduce CO₂-equivalent emissions by 65% compared to incineration.