Environmental Engineering Reference
In-Depth Information
7.4 POLYBROMINATED DIPHENYL ETHERS (PBDEs)
These compounds are flame retardants used in products such as flexible
polyurethane foams (used in upholstery), plastic appliance housing, wire
andcableinsulation, andcoatingsatweightfractionsthatcanrangefrom10
to 30%. About 67,000 tons of PBDEs were produced worldwide in 2011. Of
the thermoplastic resins, PE, PP, EVA, HIPS, and ABS resins generally use
PBDEs. Automotive, building construction, and textile upholstery sectors
each use about a quarter of the production, and electrical products account
for about another 13%. Fire protection afforded by flame retardants 12 has
very significant benefits in terms of avoided property damage and lives
saved in fires. The generic chemical structure of the class of compound
is shown below (note structural similarity to polychlorinated biphenyls or
PCBs). Structurally, there are 209 possible congeners of PBDE.
Halogenated flame retardants thermally decompose during a fire, yielding
high concentrations of bromine radicals. The highly reactive bromine
radicalscombinewiththevolatilizedflammablevaporfromburningplastics
and extract hydrogen from these, forming HBr. Removal of H and OH
radicals from the hot igniting vapors controls the heat and the fire.
Naturally, the fully brominated decabromo- congener molecule (referred to
as the BDE-209 congener) is the most effective and most widely used in this
application.
Commercial products of PBDEs are available as mixtures of several
congeners though named after the dominant component for convenience
(Allen and McClean, 2007). For instance, the commercial “penta-BDE” is a
mixture of tetra-, penta-, and hexacongeners. It was the most used flame
retardant in polyurethane foam. Penta- and octa-BDE mixtures are no
longer manufactured in (or imported into) the United States since 2004
and internationally from 2010. Only the deca-BDE is still manufactured and
 
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