Phosphorus, nitrogen and inorganics used in polyurethane chemical recycling produce PIN flame retardant recycled PUR. Glycolysis is the most widespread route for chemical recycling of polyurethanes (PUR). Glycols or glycerol (which can be bio-derived), with catalysts, are used as depolymerising agents (usually at around 180 to 240°C). This breaks chemical bonds, converting PUR polymers to oligomers (ended by hydroxyl and amine moieties) and breaking crosslinking. Seven studies are summarised which show that PIN compounds, phosphate esters or nitrogen-mineral (urea-boron) containing polyol, can be used for glycolysis of PUR then production of a PIN FR recycled PUR. Other studies show that glycolyzed PET poly(ethylene terephthalate) plastic waste can also be recycled to PIN flame retardant polyurethane (PUR).
“Materials and Chemistry of Flame-Retardant Polyurethanes”, Volume 1: A Fundamental Approach, 2021, ed. K. Gupta https://pubs.acs.org/doi/10.1021/bk-2021-1399 chapter 12, pages 265-284, “Recycling of Polyurethanes Containing Flame-Retardants and Polymer Waste Transformed into Flame-Retarded Polyurethanes”, M. Włoch https://doi.org/10.1021/bk-2021-1399.ch012