Halogenated flame retardants, environmental

Several compounds may be used as flame-retardants for PS foams but generally halogen flame-retardants are the most used even if, due to environmental and human health concerns, a continuous search for halogen-free FR is going on. A very recent detailed review on FR for PS foams is reported by Levchik and Weil,79 other useful data may be found in patent literature. 

Kolic, T.M., Shen, L., et al. (2009) The analysis of halogenated flame retardants by GC-HRMS in environmental samples. Journal of Chromatographic Science, 47(1) 83-91. 

Despite some environmental concerns, halogenated flame retardants still play an important role. With the exception of a few chlorinated products (e.g., chlorinated paraffins), these flame retardants contain usually molecules with several bromo groups (Fig. 11.18). Bromo compounds are active during combustion in the gas phase, whereas HBr reacts with OH and H radicals under formation of less reactive halogen radicals. The flame retardancy of bromo compounds is often synergistically improved by the addition of antimony oxide Sb203. 

The environmental scrutiny that has impacted halogenated flame retardants has primarily focused on brominated diphenyl oxides such as DBDPO. There is concern that these compounds release dioxins when burned. Activity has primarily been in Europe. Currently there are no legislative bans or limits on halogenated flame retardants anywhere in the world, and there are not any on the near-term horizon. However, there are some voluntary bans on selected brominated compounds (particularly DBDPO and related types) in some of the green countries of Europe. In many cases, these brominated products are replaced by other brominated products that are not under immediate suspicion. 

Environmental Considerations. The halogenated flame retardants differ greatly in environmental contamination. As mentioned already, pentabro-modiphenyl ether has become widely dispersed, but decabromodiphenyl ether much less so due to its negligible solubility and vapor pressure. Antimony trioxide also is nonmigratory because of its very low solubility and negligible vapor pressure but nonetheless is under close scrutiny from the regulatory authorities (166,207). 

In the modern polymer industry, the various existing types of polymer flame retardants based on halogens (Cl, Br), heavy and transition metals (Zn, V, Pb, Sb) or phosphorus-organic compounds reduce the risk from pol3nner combustion and p5n olysis, but may present ecological issues. The overall use of halogenated flame retardants is still showing an upward trend, but the above concerns have started a search for more environmentally friendly polymer additives. As a result it is quite possible that the future available flame retardants will be more limited than in the past. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

ENDS Report 308, September 2000. NEC unveils circuit boards free of halogen or phosphorus compounds ENDS Report 308, September 2000. NEC unveils circuit boards free of halogen or phosphorus compounds Personal communication with Magnus Bjork, IKEA, at Brominated Flame Retardants and Foam Furniture Conference and Roundtable EPA 9. San Francisco, April 2003 Personal communication with HP, H M, Boots and Sainsbury, May-June 2003 Skanska (2004) Press release from Johan Gerklev, Environmental Manager, Skanska Sweden, December 12004 Skanska (2002). Brandforsk project 706-021. See www.skanska.se UBA (2003). Precautionary Risk... 

A series of flame retardant additives for ABS have been discussed, including halogen containing flame retardants, as well as halogen free flame retardants. The latter are being preferred for environmental reasons, however, only a few are as effective as halogen containing flame retardants. For ABS blends, some flame retardants (20) have been described that are summarized in Table 8.9. 

Halogen-based flame retardants have served a great need for effective flame retardancy for several years. Due to relatively recent environmental concerns, there is a continuing trend toward the development of nonhalogenated materials to replace these systems. While this has been underway for quite some time, it does not appear that nonhalogenated materials will be available in the near future. Hence it appears that there is still a need for these materials to prevent fires. 

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