Introduction – Why Halogen-free Flame Retardants?

This website is meant to illustrate the technical properties and advantages of halogen-free flame retardants (FRs) for key application areas like housings, cables, connectors and switches as well as printed wiring boards. After many years of research and development a whole toolbox of halogenfree chemistries is now available for the materials engineer. In some areas, the development of commercial solutions is
moving quickly.

Flame retardants have become a class of chemicals which receive more and more scientific and public attention. The discussions about flame retardants started, when brominated flame retardants (BFRs) became a topic of environmental concern in the early 1990ies, when it was discovered that some BFRs could form halogenated dioxins and furans under severe thermal stress or when they were burnt in accidental fires or uncontrolled combustion1. Findings in the environment and biota and the suspicion that some flame retardants bioaccumulate in organisms have added to these concerns2 3 4 5. Meanwhile, the environmental and health properties of not only BFRs but also other types of flame retardants have been studied extensively. The most widely used organic flame retardants have become the subject of official risk assessments in Europe.

What are halogen-free flame retardants7? This group
covers a diverse range of chemicals which are commonly
classified as:

Intumescent flame retardants (mechanism see Figure 1) are an example of a typical mechanism for halogen-free flame retardants. The combustible material is separated from the fire or heat source by an insulating foam which forms at the surface. Intumescent flame retardant systems can be applied to decrease flammability of thermoplastic polymers such as Polyethylene, Polypropylene, Polyurethane, Polyesters and
Epoxy resins.

Figure 2 shows the current European consumption of different flame retardant types – halogen-free FRs do already
present the major market share. In addition, Figure 3 illustrates the variety of polymer types used for E&E installations,
which explains why so many different FR technologies are necessary, because FRs need to match polymer properties and specific processing requirements. The total European plastics demand for E&E applications was estimated at 3.15 million tons in 2004 (source: PlasticsEurope).

For cables the estimated total polymer consumption for 2007 will be 1.3 mio. tons, dominated by PE (52 %) and PVC (40 %). Other materials make up the remaining 8 %. Low smoke, zero halogen cables have been growing strongly in Europe and reached a consumption of 93 000
tons of polymer compounds in 2005 (source: AMI Consulting, UK).

o Inorganic: This category comprises mainly metal hydroxides
like aluminium hydroxide and magnesium hydroxide.
Other compounds like e.g. zinc borate are used to a
much lesser extent.
o Phosphorus based flame retardants include organic and
inorganic phosphates, phosphonates and phosphinates
as well as red phosphorus, thus covering a wide range
of phosphorus compounds with different oxidation
states.
o Nitrogen based flame retardants are typically melamine
and melamine derivatives (e.g., melamine cyanurate,
melamine polyphosphate, melem, melon). They are
often used in combination with phosphorus based
flame retardants

Over the past decade, the fate of electronic waste and the contained hazardous materials have gained increasing political attention and have led to the WEEE8 and RoHS9 Directives in Europe: The aim of these regulations is that electronic waste shall be properly recovered and recycled; new equipment shall not contain problematic substances. Flame retardants are affected, because according to the WEEE directive, plastics containing brominated flame retardants have to be separated before further treatment of the waste. Under RoHS, certain brominated flame retardants10 are no longer allowed in new electronic equipment since July 2006.

Other regions of the world are about to follow with similar legislation. These activities increased the interest in halogenfree flame retardants, not only in engineering plastics but also in thermoset resins and printed wiring boards. In addition to legal requirements, ecolabels have been introduced since the 1970ies as voluntary measures in order to promote environmentally friendly products. The idea is that the consumer can make a conscientious decision for such products, if they are labelled according to an accepted and respected scheme. Worldwide, today, there are about 25 ecolabel organizations and schemes (see: http://www.gen.gr.jp). Even in Europe there are several national labels in addition to the EU flower. Ecolabels are specifically designed to go beyond legal requirements like RoHS, because they are meant to endorse the “best in class” and advance environmental benchmarks. Traditionally, many ecolabel systems have prohibited the use of halogenated flame retardants in their criteria for electronic products (e.g. EU label, Blue Angel in Germany, Nordic Swan in Scandinavia, TCO in Sweden). Often, the flame retardants which are used in products need to be declared to the ecolabelling organization. Ecolabels are also relevant for green public procurement, because e.g. in Europe ecolabel criteria can be included in public calls for tender.

Due to this regulatory and environmental pressure, a number of original equipment manufacturers (OEMs) have developed phase out plans for BFRs, some have even made strong commitments with deadlines e.g.

o Apple has made the commitment to ban all BFRs by the end of 2008: http://www.apple.com/hotnews/agreenerapple/
o Dell’s policy states that it intends to move away from chemicals that are persistent, bioaccumulative and toxic.It has also pledged to eliminate all brominated flame retardants and PVC from new product designs by 2009. http://www.dell.com/downloads/global/corporate/environ/report07.pdf
o In Nokia’s most recent list of restricted substance, BFRs are also no longer permitted for new products: http://www.nokia.com/NOKIA_COM_1/Corporate_Responsibility/Environment_/Built_green/Substance_management/NokiaSubstanceList_Version_10.xls
o Sony Ericsson also restricts halogenated flame retardants: http://www.sonyericsson.com/images/spgd/CWS31AFW_15308_27_0_4001.pd