The Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronic Equipment (WEEE) directives of the European Union earlier this decade added emphasis to the worldwide recognition of the effects that chemical compounds have on the health and safety of both humans as well as the planet. In response, several large corporations, including Apple Computer, Nokia, Dell and Sony Ericsson, are developing plans to phase out brominated flame retardants (BFRs). While Nokia has already phased out BFRs, Apple has committed to banning all of them by the end of 2008, and Dell has committed to doing the same by the end of 2009.
In addition, antimony compounds, which are used as synergists with many brominated flame retardants, have come under close scrutiny. Antimony compounds are now on the European Union’s list of high-priority substances to be considered for inclusion on the RoHS list, which would ban their use in all 27 European Union nations.
Meanwhile, the Swedish government has lifted its unilateral and limited ban on the use of flame retardant decabromodiphenyl ether (Deca-BDE) in textiles, furniture and some electronic cables in response to a legal challenge from the European Union. This removed the inconsistency between its ban and the positive results of a 10-year EU risk assessment of the material which did not identify any significant risk in its use. This has left the EU with the nagging problem of how to resolve the contradiction between the RoHS Directive’s restriction on Deca-BDE and the positive scientific evaluation of Deca-BDE.
Role of ecolabelling
Ecolabelling, a voluntary system to identify consumer products that avoid negative environmental effects, has also had a pronounced effect on the use of BFRs. Ecolabels are specifically designed to go beyond legal requirements, such as RoHS and REACH, and support best-in-class products and services that use advanced environmental benchmarks. Many eco-label systems prohibit the use of halogenated flame retardants in electronic products and require declarations from eco-label organizations stating their absence. Eco-labelling also plays a role in procurement, as various eco-labelled approved products and processes can be included as criteria in the bidding process.
The result is a confusing set of standards for producers and consumers of BFR-containing materials and a requirement that many of these issues be resolved in a relatively short period of time. This has forced many manufacturers to implement intensive programs to address policy and regulatory changes as they occur.
Solution Trends
As brominated flame retardant materials are phased out, flame retardant suppliers are launching new materials to replace them. Since most current alternatives are less efficient than BFRs, these new flame retardants will build on the system. In other words, a group of different flame retardants will be assembled based on customer needs. However, this requires extensive R&D work to determine which system is suitable. For consumers, there are a multitude of new options available. What complicates matters is the fact that many of these changes occur under tight deadlines, leading to a mad scramble to find a system that works, not necessarily one optimized for the manufacturer’s process and end use of the product.
Nanocomposite materials, especially clays and graphite, have shown promise as flame retardants. Nanocomposites work by creating a carbon-like protective layer and cross-linking the polymeric matrix. This results in char formation and a reduction in the rate of heat release. Char is the crust of partially burned material that forms on the surface of plastic material in a fire and robs the flame of fuel. Many companies have begun to market nanocomposite concentrates as flame retardants, often combining them with magnesium hydroxide or aluminum trihydrate to improve overall performance.
Intumescent flame retardants, which foam at combustion temperatures to help form a thick layer of insulating carbon, have also seen increased activity. These FRs have limited applications due to issues of cost, poor processing, thermal stability, deposition, and water sensitivity. Most of these flame retardants are melamine or phosphorous based compounds.
Tin-based flame retardants are increasingly used as substitutes for antimony-based materials. Tin functions as a char promoter in the resin substrate in both the vapor phase and the condensed phase. Zinc stannate and hydroxystannate have been recommended for use as smoke, flame, and carbon monoxide suppressants when used as synergists with brominated flame retardants.
In general, the changing environmental climate will continue to force both suppliers and consumers of flame retardants to improve the impact that current materials have on human health and the environment. This will require suppliers to constantly stay abreast of new developments in the global regulation of these materials, as well as any new, more benign compounds they may use to differentiate themselves from their competitors.