Chemical recycling of WPU to FR PET
Waste PET was glycolysed and reacted with a PIN FR to generate flame retardant waterborne polyurethane (WPU). Waste PET (polyethylene terephthalate) has hydrolysed by heating to c. 200°C with a non-metallic, non-halogenated nitrogen-containing ionic liquid (1-ethyl-3-methylimidazolium acetate). The phosphorus-nitrogen PIN biological molecule N1112OHDHP (choline dihydrogen phosphate) was then added. Adipic acid and 1,4-butanediol were added to polymerise flame retardant waterborne polyurethane (WPU), which was processed to film. Particle size of the formed WPU, mechanical and fire performance properties of the WPU film were tested, achieving good mechanical properties and UL94 V-0 with 2.5% loading of choline-DHP and nearly 50% reducing in total heat release with 7.5% choline-DHP. The authors conclude that this process offers a low-energy, environmentally friendly and simple route to recycle PET waste to flame retardant WPU.
“One-pot Preparation of Flame-retardant Waterborne Polyurethane by Glycolysis of PET with Ionic Liquids”, K. Xu et al., Polymer Degradation and Stability, vol. 233, 2025, 111146 https://doi.org/10.1016/j.polymdegradstab.2024.111146
