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Investigation of brominated flame retardants present in articles being used, recycled and disposed of in New Zealand

• Executive Summary
• 1. Introduction
• 2. Estimate of the amount of BDE in New Zealand
• 3. Assessment of the fate of BDEs in waste
• 4. Profile of BDE flows in New Zealand
• 5. Risk analysis
• 6. Environmentally sound disposal methods
• 7. Limitations of the study
• 8. Conclusions and Recommendations
• Additional readings
• Appendix A Detailed data tables
• Appendix B Polybrominated Diphenyl Ether (PBDE) structure and physical properties
• Appendix C Analytical equipment and procedures
• Appendix D Certificate of analysis
• Appendix E Methods and analysis of consumer products
• Appendix F Calculating the % BDE present in consumer products
• Appendix G Details of the selected landfills and the sampling of leachate
• Appendix H Current status of the flame retardant industry
• Appendix I Non-dust sources of BDEs more prominent human intake
• Appendix J Completed Questionnaire SC-4/19 for submission of information on new POPs in accordance with SC-4/19
• Appendix L Questionnaire for organisations that manufacture articles containing BFR’s
• Appendix M Excel spreadsheet entitled ‘XRF analyser raw data’
• Appendix N Excel spreadsheets entitled ‘NZ Statistics data giving categories with raw data’

Appendix B Polybrominated Diphenyl Ether (PBDE) structure and physical properties

The flame retardancy of polybrominated diphenyl ethers (PBDEs) increases with the number of bromine atoms in the molecule. Therefore only the higher brominated BDEs like Penta, Octa or Deca are of commercial interest.

The general chemical formula of polybrominated diphenyl ethers is:

PBDEs have many congeners depending on the number and position of the bromine atoms on the two phenyl rings. The total possible number of congeners is 209, and the number of isomers for mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- and deca BDE are: 3, 12, 24, 42, 46, 42, 24, 3 and 1, respectively.

PBDEs are produced by the bromination of diphenyl ether. Technical OBDE may be produced by the reaction of diphenyl ether with eight equivalents of bromine in the presence of Al₂Cl₆/Al₂Br₆ first at 35 ^oC and then at 120 ^¡C. Technical PeBDE is synthesized by treating diphenyl ether with five equivalents of bromine at 30-65 ^¡C in the presence of powdered iron.

Commercial or technical grade PBDEs are generally mixtures which are in part a result of the production process (impurities). For example, HexaBDE is not purposefully produced, but almost always as a by-product of the Penta or Octa BDE production. The compositions of commercial BDEs are given in table 1 below.^{Footnote 15}

However there are many variations like^{Footnote 16}:

Commercial DeBDE was the most widely used flame retardant in the world in 2001²with OBDE being the second most widely used (largely in acrylinitrile-butadiene-styrene (ABS) polymer (12 – 18% by weight) in computer and other business machine cases / cabinets. However, OBDE is being phased out and replaced by tetrabromobisphenol (TBBP-A) as this is stable in UV light, while OBDE is not.

Another advantage is that TBBP-A is chemically bonded to the polymers while PBDEs are just physical blends. During abrasion or corrosion of the polymers PBDEs escape more readily to the environment while TBBP-A will still be bonded to the polymers. It is mainly used in printed circuit boards and in ABS which is used in TV’s.

Another ‘more modern’ brominated flame retardant is hexabromocyclododecane (HBCD) which has 16 stereo isomers of which the most common are:

HBCD is mostly used in Extruded (XPS) and expanded (EPS) polysterene at resp 0.7 and 2.5%^{Footnote 17}

Physical properties

A few physical properties of BDEs are presented below in the form of graphs, called homologe series, to show the relationship between the various compounds and their dependancy on their molecular make up.

In Figure B.1 the octanol – water partitioning coefficient is shown in relation to the number of bromine atoms. Clearly the higher the bromination the higher the affinity of the compound to reside in the octanol phase. Among other things this explains the very low solubility of BDEs in water.

This is shown in Figure B.2 where clearly the higher brominated compounds display a lower solubility. Note the scale is logaritmic. The much higher solubility underlies the higher toxicity of the lower brominated coumpounds. Unfortunately, as is described later in this report, the higher brominated coumpounds degrade in the environment into the lower brominated compounds.

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Figure B.3 shows the vapour pressure, or the ease of evaporation. At bromination of 5 bromine atoms and higher the vapour pressures are very low, at 10^-5 to 10^-6 Pascal at 21 ^oC. This means the BDE’s used as flame retardants are unlikely to evaporate quickly at room temperature and equally unlikely to evaporate out of landfills. However at higher temperatures (during a fire) they do evaporate and fall apart releasing free bromine which binds with the combustible materials before oxygen can and thereby extinguishing the fire.

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Commercial Brominated diphenylethers (BDE’s)

The commercial BDEs have their own CAS (Chemical Abstract Services) identification number which sets them apart from the individual congeners. In time, due to changing production processes the composition has changed. Some manufacturers also produce different blends.

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