Phosphorus PIN FR for PBT recycling
A phosphorus PIN flame retardant copolymer achieved UL 94 V-0 in waste PBT chemically recycled to PBAT. Waste PBT (polybutylene terephthalate) was chemically depolymerised to BHBT (butylene terephthalate) at 225°C – 2 hours with a zinc argon catalyst. The PIN FR copolymer, 2-carboxyethyl (phenyl) diphosphinic acid dihydroxybutyl ester (BHBcept), was produced by reacting 3-hydroxyphenylphosphinyl-propanoic acid (CEPPA) with BHAT (butylene glycol adipate). The biodegradable polymer PBAT (Polybutylene terephthalate/butylene terephthalate) was then copolymerised with this PIN FR copolymer. The inclusion of 5%-mol CEPPA (c. 0.7% P content) increased LOI of the PBAT by around 50%, reduced peak heat release rate by 20% and achieved UL 94 V-0 (3 mm), but increases smoke release by +17% and deteriorates mechanical properties significantly compared to neat PBAT.
“Preparation of PBAT Copolyesters with Flame Retardant and Degradable Functions through PBT Chemical Alcoholysis and Closed-Loop Recycling”, J. Liu et al., ACS Sustainable Chem. Eng. 2024, 12, 17301−17318, https://doi.org/10.1021/acssuschemeng.4c07032
