Alkaline solvothermal debromination of commercial brominated acrylonitrile butadiene styrene (ABS)

Acrylonitrile-butadiene-styrene (ABS) is one of the most common thermoplastics and for decades, brominated fire retardants (BFR) were the primary compounds added to comply with fire safety regulations in electronic and electrical polymeric components. BFRs are effective at low concentrations, are stable up to 250 °C (sufficient for thermoplastic processes such as injection moulding), and are compatible with polymers (easy addition). However, their hazardous nature and environmental persistence sparked concerns about their use, which limits the possibility of recycling them. Currently, most of them are banned or have limitations on their application and concentration. Here, we report an alkaline solvothermal treatment to debrominate commercial ABS from end-of-life products (up to 97 %). The process operates between 160 °C to 190 °C with ethylene-glycol as solvent and KOH as extraction agent (1 M ). It removes 95 % of the Br in 4 h above 160 °C and 97 % at T = 160 ∘ C and 24 h. FTIR spectroscopy confirms that 30 % of the acrylonitrile reacts to form acrylic acid in the most aggressive conditions. Curiously, the T g increases by up to 10 °C, which might improve the mechanical properties of the polymer. • Achieved 95% Debromination in 4h at 160° C and 97 % in 24h at 160° C • Up to 10 °C increase on the glass transition temperature after the treatment • Thermochemical changes might improve the mechanical properties of the polymer • FTIR detects a partial conversion of the acrylonitrile group into acrylic acid.