Refractory Plasmonic Nanoparticles for Visible Light Mediated Recycling of Epoxy

Epoxy polymers exhibit excellent mechanical properties and have wide applications ranging from adhesives to structural materials. However, recycling of epoxy is difficult because of their irreversible cross-linked network structure. We have developed a reversible epoxy which can be recycled using visible light. Diels-Alder chemistry is studied to develop thermo-reversible epoxy. At higher temperatures (above~ 120°C), the Diels-Alder reaction reverses, resulting in depolymerization of the epoxy and can polymerize again as it cools down. Photothermal refractory plasmonic titanium nitride (TiN) nanoparticles are incorporated in the reversible epoxy. These nanoparticles can efficiently absorb visible light and convert that to heat to promote the retro Diels-Alder reaction. The nanoscale heating can efficiently break the chemical bonds increasing rate of depolymerization.   TiN nanoparticles were well dispersed in the epoxy matrix using optimized probe sonication method. The photothermal reversible epoxy composite was characterized using FTIR, UV-Vis spectroscopy and rheometer. The depolymerization of reversible epoxy could be achieved with 0.1 wt% loading of TiN at light intensity of 1420 W/cm². Funding: U.S. Department of Energy, Office of Basic Energy Sciences, DE-SC0022261.