Recycling PET to carbon dot PIN FRs

Post-consumer bottle PET was one-step recycled to c. 2 nm functionalised carbon spheres, tested as PIN FR in PBT. The PET was shredded, cleaned and dried, then reacted with ethanolamine (1500 g PET to 975 ml MEA) at 280°C for 18 hours (pyrolysis). Resulting sold was filtered, dried and ground. This generated ‘carbon dots’: near-spherical carbon spheres with average diameter 2 nm, rich in surface functional groups (carboxyl, hydroxl …). 5% loading of the carbon dots in poly butylene terephthalate (PBT) reduced peak heat release rate by nearly 30% and increased LOI by nearly 50% (compared to neat PBT). The carbon dots are considered to act by developing protective surface char on the PBT (because of the surface functional groups) and by releasing CO₂ and by delaying decomposition and so burning of the PBT

“Kilogram-scale upcycling of waste poly(ethylene terephthalate) into carbon dots as efficient flame retardants for poly(butylene terephthalate) composites”, M. Chaohui et al., Polymer Degradation and Stability 249 (2026) 112087 https://doi.org/10.1016/j.polymdegradstab.2026.112087

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