Detailed review of technologies, implementation and perspectives for recycling of flame retardant polymers. Based on over 230 references, of which nearly 30 are summarised in a table, this review covers recycling of different polymers with PIN and with halogenated FRs, including thermosets, thermoplastics and new solutions such as vitrimers and covalent adaptable networks. A key challenge is considered to be the sorting and separation of plastics containing brominated FRs, as required by legislation because certain BrFRs are banned (total bromine < 0.2%). The authors noted that recovered WEEE plastics often remain contaminated by these, and that around half of EU WEEE waste is not being properly sorted. For PIN FR thermoplastics, mechanical recycling is the best option, for sustainability and cost, but with challenges to maintain mechanical and fire performance. The polymer matrix and the specific FRs strongly impact recycling and mixed waste streams are difficult to reprocess. Thermoplastics can be mechanically recycled by shredding to flakes which can be used as fillers in new polymer compounds. Solvent, thermochemical and pyrolysis recycling routes pose questions of energy efficiency, emissions and costs. The authors identify as highlights: development of energy efficient recycling routes, importance of sorting of halogenated FR containing wastes, avoid halogenated releases in processing, need for more sustainable recycling processes for thermosets and need to ensure that future polymer compounds are designed for recycling.
“Recycling of flame retardant polymers: Current technologies and future perspectives”, A. Bifulco et al., J. Materials Science & Technology 2024, https://doi.org/10.1016/j.jmst.2024.02.039