Flame retardants for an effective recycling of expanded polystyrene (EPS)

Published by Dr. Christian Sinn, Dr. Christoph Semisch, Prof. Dr. Michael Braungart und Dr. Peter Mösle in “Müll & Abfall” 10|2019

Abstract

Pure EPS is inflammable. Therefore, the addition of a flame retardant is mandatory, if EPS is – like any other organic insulation material – used for insulation of buildings. For many years HBCD was used as a flame retardant in EPS. However, after revealing its toxicity, used EPS became hazardous waste and better alternatives had to be found. In this study two brominated organic compounds were assessed for their environmental and health risk during use as flame retardant in EPS.

Polymeric FR, a new brominated polymer, is non-toxic and non-bioaccumulative. Combustion leads to the formation of hydrogen bromide which is intended for flame retardancy. Under certain conditions, traces of toxic organic compounds may be formed.

In contrast to Polymeric FR, the second flame retardant, a TBBPA derivative, is very hazardous. This substance is endocrine disrupting in vitro, bioaccumulative and persistent. Identification of the TBBPA derivative in environmental samples proves that the substance can disperse and accumulate in the environment. For final confirmation of its toxicity, currently, the TBBPA derivative is assessed by the EU. It may be possible that the use of the substance will be restricted after completion of this process in a few years.

Similar to Polymeric FR, the TBBPA derivative forms hydrogen bromide during combustion. Under certain conditions, traces of highly toxic organobromine compounds can be formed. Moreover, research has shown that the TBBPA derivative is slowly degraded under anaerobic conditions, leading to even more toxic metabolites, e.g. to its precursor substance TBBPA which is suspected of being carcinogenic and endocrine disrupting. It is recommended not to use this substance any longer due to its hazardous characteristics.

As the brominated polymer is neither toxic nor bioaccumulative due to its polymeric character, it is clearly superior to the TBBPA derivative in its environmental and health performance. Additionally, the use of this compound allows the mechanical recycling of EPS after use and thereby saving of fossil resources and reducing carbon dioxide emission.

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