2024 AIChE Annual Meeting
Recycling of Epoxy with Solar Light
Madeline Finale, Jonathan Logan, Arnob Saha, Matthew Durfee, Nicole Penner, John McCoy, Youngmin Lee and Sanchari Chowdhury
Epoxies are a strong polymer commonly used as structural material. However, because of the irreversible crosslinking of epoxy, it can’t be reliquefied once it’s cured, which makes their recycling challenging. To address this challenge, we are modifying epoxies with a thermo-reversible Diels-Alder reaction and doping with photothermal nanoparticles to provide the required heat using sunlight. We used Titanium Nitride (TiN) nanoparticles and Carbon Black nanoparticles as the photothermal nanoparticles which can absorb broad spectrum sunlight very strongly.
The photothermal nanoparticles are well dispersed in the furan precursor and then reacted with maleimide to synthesize a Diels-Alder epoxy nanoparticle composite. The composite powder was then compressed into a mold and exposed to visible light for recycling.
The epoxy could be recycled efficiently twice with 10 sun intensity light. The recycled samples were tested for their mechanical strength with a 3-point bend test. We compared he flexural modules for the light recycled and conventional heat recycled samples with the pristine samples. We found that pristine samples with or without nanoparticles, have similar flexural modulus. This is because with the loading of 0.5 weight percent, nanoparticles had no effect on the mechanical properties of the epoxy. Interestingly, the first light recycled samples had superior flexural modulus in comparison to the pristine samples. No such effect was observed for the heat recycled samples. This is attributed to the fact that in case of photothermal heating the reaction is more efficient as the nanoparticles can absorb light to generate nanoscale heating to generate volumetric heating.
In summary, our work showed that we could achieve full recycling of epoxy using sunlight without compromising it’s mechanical properties, which can open up a possibility of using renewable energy for recycling epoxy.