Recyclable reactive P-FR epoxy

Research tests show solvent recyclable DOPO-reacted itaconic acid epoxy resin (reactive PIN phosphorus flame retardant). At lab scale (250 ml), the P-FR DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) was reacted with itaconic acid (which can be derived from citric acid or by fermentation). This was reacted with a nitrogen-containing triazine derived from 2-aminothiophenol (ATP) and trimeythylpropane to give a hyperbranched epoxy resin (IA-EHBP). This epoxy showed good strength and toughness. At 0.6% phosphorus content, the epoxy achieved UL 94 V-0 (3 mm). The organic solvent tetrahydrofuran with phosphoric acid was used to recycle the epoxy (8 hours) followed by sodium hydroxide neutralisation. This showed c. 80% recovery of DOPO itaconic acid and of ATP.

“Closed-Loop Recycling of Tough and Flame-Retardant Epoxy Resins”, F. Wei et al., Macromolecules 2023, 56, 5290−5305, https://doi.org/10.1021/acs.macromol.3c00650