Hangzhou, China – The thermoset nature of polyurethane foam continues to make it a challenge to recycle, and while methods for chemical recycling show promise, the majority is still either mechanically recycled or ends up in landfill. An alternative has been developed by scientists at Zhejiang University, who have found a way to upcycle PU foam into resins for 3D printing.
First, the foam is ground up, and these fragments are soaked in dimethylformamide in the presence of a catalyst, chosen according to the foam’s chemistry. This chemically fragments the PU network into a dissolvable mixture under mild conditions.
This fragmented material was then used to make new polymer networks. The single network material was then turned into an interpenetrating double network with the addition of network reforming additives, photo pre-curing and thermal post-curing. The mechanical properties of the resulting 3D photo-printable materials can be tuned.
The scientists suggest that the process is both easy to implement and economically attractive, and can be recycled once more after printing. They also they believe the technique can be expanded to other commodity thermosets.
The work has been published in the journal Nature Chemistry.