Debromination of high impact polystyrene for polymer recycle

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Polystyrene (PS) ranks among the most abundant thermoplastic polymers with a world demand of 6.4 million metric tons (Mt) in 2016, and it grows 2.3 % every year. PS applications range from packaging to electronic devices (comprising general-purpose high-impact polystyrene -HIPS) to non-biodegradable packaging. Brominated flame retardants (BFR) are added to HIPS in electronics to reduce fire hazard, but its environmental toxicity is greater than traditional PS, since it bioaccumulates. The global waste electric and electronic equipment (WEEE) reached 44.7 million Mt in 2016 and will grow to 52.2 million Mt by 2021. The Chinese ban of plastic waste import has increased the amount of WEEE Canada will have to deal with and the amount of WEEE containing Br-HIPS will reach the recycling stream for many years to come. Technology development is therefore a necessity. Finding a methodology to debrominate Br-HIPS will reduce the environmental burden and increase the recyclability of HIPS, preventing it from reaching landfills and open dumps, treated in an unsustainable manner, while at the same time fulfilling the need for virgin HIPS. ***Techniques to debrominate HIPS include supercritical water and pyrolysis, which degrade HIPS eliminating the possibility of recovering it. Lavergne Group has seized this opportunity and has created a business model to treat this waste. They approached Polytechnique Montréal to conceive and design a scalable procedure to remove bromine from HIPS to recycle the several kilotons (and more) of Br-HIPS that they have in stock in Quebec. We have already identified and tested technology to debrominate Br-HIPS using a solvent-treatment that prevents the degradation of PS, while maintaining its recyclability in regular process lines. ******The ability to measure precisely Br in the liquid phase and solids phase is critical to the success of this program. However, few analytical techniques are capable of measuring bromine precisely. No facilities are available in the Montreal region currently. X-ray fluorescence (XRF) is the qualitative and quantitative tool universally adopted for a variety of end-of-life plastics containing brominated flame retardants. Indeed, it is the analytic technique that is in compliance with European Union (EU) and United Nations Environment Programme (UNEP). XRF is a non-destructive technique to quantify elements from sodium to uranium, able to determine concentrations from the ppm to 100% in less than 30 min, giving reliable results and with low maintenance cost.**