ORNL upcycling process doubles the strength of ABS for 3D printing
By DE StaffAdditive Manufacturing
Researchers say technique makes common AM feedstock significantly more reusable.
Researchers at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL) announced the development of an upcycling technique that converts discarded plastics for reuse in additive manufacturing.
According to the research team, it was able to upcycle waste ABS thermoplastic into LEGO blocks using fused filament fabrication (FFF) 3D printing technology. The result was a plastic that displayed enhanced strength, toughness and chemical resistance over standard ABS.
“We will need fundamental discoveries to overcome the challenges of increased costs and deteriorating material properties associated with recycling,” said lead author Tomonori Saito of ORNL’s Chemical Sciences Division. “Our goal was to develop an easily adoptable strategy that reuses plastic waste to create a more valuable material instead of generating fresh plastic.”
FFF printing requires materials that can be extruded through a heated nozzle to form the threads of 3D structures, layer by layer. ABS is commonly used for this process because it can flow easily and harden quickly into strong, rigid structures.
To improve upon the process, the ORNL team applied “click” chemistry to convert the chemical makeup of ABS into a vitrimer, a type of polymer that combines the processability and recyclability of thermoplastics with the mechanochemical properties of thermosets, which aren’t compatible with FFF. According the researchers, the synthesis uses widely available medical compounds that are mixed in a single step under mild conditions, followed by curing with heat.
The result was an upcycled ABS that’s roughly twice as tough and strong of standard ABS, with enhanced solvent resistance. 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.
“This effort demonstrates a closed-loop for manufacturing plastic items, potentially with higher value and performance, using only existing plastic waste in one of the most accessible areas of additive manufacturing,” said Saito.
The research study on the ORNL technique was published the journal Science Advances as “Closed-loop Additive Manufacturing of Upcycled Commodity Plastic through Dynamic Crosslinking.”