Recycling of EPS waste to PS granules free of HBCDD

Expanded and extruded polystyrene (EPS and XPS) belong to the most often used insulation materials and - with respect to this application- both materials have been equipped with the brominated flame retardant hexabromocyclododecane (HBCDD) for more than 50 years. After HBCDD had been identified as a substance of very high concern, it was set under control of the Stockholm Convention and the European REACh legislation.  In consequence, the use of HBCDD in insulation materials is currently phased out and waste insulation material made of HBCDD equipped EPS or XPS cannot further be subjected to state-of-the-art mechanical recycling.

However, as the majority of the formerly produced HBCDD equipped EPS and XPS is still in use as insulation material, more sophisticated recycling approaches are currently investigated.

This study investigates a solvent based recycling process, which dissolves polystyrene from insulation waste and eliminates not only insoluble waste components but also co-dissolved HBCDD. The study investigates the efficiency of HBCDD removal as well as mechanical properties of recycled PS produced by this process.

Results indicate a save separation from inorganic waste and other non-target polymers as well as an extraction of more than 99.6% of initially present HBCDD. Mechanical properties of recycled PS are in the expected range of virgin general purpose PS as long as the separation of residual solvents from the recycled polymer is sufficient, i.e. residual solvent content < 0.1%.