A Multi-Step approach for the chemical recycling of Flame-Retardant PBT Composites: Environmental and economic benefits

The extensive use of flame-retardant polyester composites, notably polybutylene terephthalate (polybutylene terephthalate, PBT), has resulted in a growing accumulation of non-biodegradable plastic waste, posing significant challenges to both environmental sustainability and resource recovery. These materials, which contain brominated flame retardants and inorganic fillers, are resistant to conventional recycling methods, contributing to long-term ecological risks. In this study, we propose a comprehensive chemical recycling strategy for post-consumer flame-retardant PBT composite materials (PBT-FrCM), integrating staged depolymerization, solvent extraction, and monomer purification to achieve efficient recovery and reuse of all major components. The recovered monomer, bis(4-hydroxybutyl) terephthalate (BHBT) (99.7% purity), brominated flame retardants (99% recovery), and inorganic fillers were successfully reintegrated into regenerated flame-retardant PBT composites (rPBT-FrCM) that exhibit mechanical and flame-retardant properties comparable to those of virgin materials. Life cycle assessment demonstrates that the process reduces greenhouse gas emissions, while highlighting energy consumption and solvent toxicity as key areas for improvement. An economic evaluation indicates that recycling 1 tonne of waste PBT generates a net value of 5041 CNY, illustrating the dual environmental and economic benefits of this approach. These findings underscore the potential of closed-loop upcycling for engineering plastics and provide a scalable pathway toward a more circular, climate-resilient material economy.