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Deca-BDE and Alternatives in Electrical and Electronic Equipment 1 Introduction
By the European Commission decision of 13 October 2005 (2005/717/EC), "DecaBDE in polymeric applications" was added to the Annex to Directive 2002/95/EC, the RoHS Directive . The background for the exemption, and the history of this development in Europe, has recently been reviewed by the Washington State Department of Health and the Washington State Department of Ecology, and the reader is referred to this source for a quick overview [[1]]. 1.1 MethodologyThis report summarises information on the use of Deca-BDE and its alternatives in electrical and electronic equipment. The information has mainly been obtained from the literature and from public information available on the web-sites of manufacturers, trade organisations, institutions, etc. Due to the nature of the study, comprising part of the scientific documentation to support a case before the Court of Justice of the European Communities, all information sources consulted, except for market surveys that are not authorised to be passed to third parties, are to be enclosed with the report submitted to the Court of Justice. This requirement also applies to personal communications, and consequently, only very limited information obtained through personal communications with companies and trade organisations is quoted in the report. The usual practice of guaranteeing confidentiality to information sources within companies has therefore not been possible, which obviously reduces the opportunities for obtaining and presenting new and updated information. Even beyond the concern of disclosing company-specific information, several companies have explicitly expressed their reluctance at being exposed as contributors to the study. In particular, these limitations may have seriously compromised the comprehensiveness of the evaluation of the potential costs of substitution of Deca-BDE. Moreover, in response to requests for updated information on the use of Deca-BDE in Europe, the four organisations: CEFIC, EFRA, BSEF and EBFRIP have jointly responded that, in view of current legal proceedings, they were not in a position to respond to the requests [[2]]. The information on the use of Deca-BDE presented in this report has consequently been obtained mostly by combining information from a variety of published sources. 1.2 DefinitionsAs mentioned above, the Commission’s exemption refers specifically to "DecaBDE in polymeric applications". Deca-BDE Polymeric applications The Kirk-Othmer Encyclopedia of Chemical Technology introduces the chapter on polymers with the following: "Polymers are the materials from which plastics, rubbers, and most fibers, surface coatings, and adhesives are made. Biopolymers are important constituents of living organisms." [[4]] Wikipedia, the free web encyclopedia, introduces the term polymer as follows: "Polymer is a term used to describe a very large molecule consisting of structural units and repeating units connected by covalent chemical bonds. The term is derived from the Greek words: polys meaning many, and meros meaning parts [1]. The key feature that distinguishes polymers from other molecules is the repetition of many identical, similar, or complementary molecular subunits in these chains."[[5]] Examples of natural polymers are cellulose, wool or caoutchouc (natural rubber). Synthetic polymers are made from one or more synthetic monomers and form the basic matrix of a range of materials like plastics, silicones and synthetic rubbers. Polymers are seldom used in their pure forms in electrical and electronic equipment; instead, the base polymer is usually mixed or chemically combined with a number of additives: pigments, stabilisers, flame retardants, fillers, etc. to form different types of plastics, rubbers and silicones. In the same manner, the cellulose base polymer is naturally combined with other substances to form wood. In the following text, the base polymer (or monomer) will be designated as the “resin”. Therefore, the term "polymer applications" is considered here to apply to all materials used in electrical and electronic equipment (EEE) that are based on polymers: plastics, rubbers, silicones, wood, textiles. In practice, plastics account for nearly 100% of the applications of Deca-BDE in EEE, so the study has focused on these applications. However, it cannot be ruled out that small amounts of Deca-BDE may be used with other polymeric applications. 1.3 Fire regulations and material classificationsThe use of plastics in electrotechnical products entrains special fire precautions because fire hazard is inherent in any energised equipment. Potential ignition sources within electrical and electronic equipment include overheated current-carrying parts, overheated terminals, sparks and arcs. When a part is ignited, flames may develop and migrate to adjacent combustible materials. Special fire tests have been developed to simulate as realistically as possible actual ignition risks. A large number of standards and test procedures for electrotechnical products exist, both internationally (IEC) and at national/regional level. In the EU, consumer electronics such as TV-sets, amplifiers, CD-players, tape recorders, etc. are regulated by standard EN 60065. This standard describes a series of test methods that have evolved from the American Standard UL 94 (see below). EN 60065 includes no flammability requirements for plastic materials, which are otherwise well protected from internal ignition sources by means of fire enclosures or minimum distances from potential ignition sources. For TV-sets, back plates and front plates are permitted to be made from materials that fulfil the requirements of the UL 94 horizontal burn test, HB (see below). The requirements of EN 60065 are different from those of the American standard (UL 1410) which, among other things, has stricter flammability requirements for TV-set enclosures. [32] Electronic products such as computers, printers, telephone systems, photocopiers and other office machines are regulated in the EU by EN 60950, which has essentially the same flammability requirements as the international (IEC 950) and the American (UL 1950) standards [32]. Standard 60950 comprises several different test methods and classifications for the different parts from which appliances are made. These test methods for materials have also evolved from the American Standard UL 94. Electrical household appliances are regulated by the European standard EN 60335. This standard has a number of sub-standards depending on the type of appliance - washing machine, hairdryer, vacuum cleaner, etc. When the efficiency of flame retardants or the flame retardancy of plastic materials is compared, the UL 94 flammability classification is usually applied. UL 94 tests on plastic materials There are two types of pre-selection test programs conducted on plastic materials to measure flammability characteristics. The first program determines the material’s tendency either to extinguish or to spread the flame once the specimen has been ignited. This is described in UL 94, The Standard for Flammability of Plastic Materials for Parts in Devices and Appliances, which is now harmonized with IEC 60707, 60695-11-10 and 60695-11-20 and ISO 9772 and 9773. The second test program measures the resistance of the plastic to electrical ignition sources. The material’s resistance to ignition and surface tracking characteristics is described in UL 746A, which is similar to the test procedures described in IEC 60112, 60695 and 60950. [[6]] UL 94 flammability classifications Six of the classifications relate to materials commonly used in manufacturing enclosures, structural parts and insulators found in consumer electronic products (5VA, 5VB, V-0, V-1, V-2, HB). The other six classifications are assigned to low-density foam materials commonly used in fabricating speaker grills, sound-proofing material and very thin films – all materials that are generally not capable of supporting themselves in a horizontal position. Horizontal versus vertical testing orientation A HB flame rating indicates that the material was tested in a horizontal position and was found to burn at a rate less than the specified maximum. The three vertical ratings, V-2, V-1 and V-0 indicate that the material was tested in a vertical position and self-extinguished within a specified period of time after the ignition source was removed. The vertical ratings also indicate whether the test specimen dripped flaming particles that ignited a cotton indicator located below the sample. In testing for the strictest 5VA or 5VB classification, UL 94 describes a method in which the test flame is applied five times. These small-scale tests measure the propensity of a material to extinguish or spread flames once it has been ignited. Material classification range The ignition resistance of a plastic part depends also on the thickness of the part - a thicker part (made of the same plastic) being more resistant. Along with the flammability classification of a plastic material, the thickness of the material would usually be specified as well. A certain plastic compound may, for example, be classified V-0 at 1/8-inch (~0.32 cm) thickness, but only V-2 at 1/16-inch (~0.16cm) thickness. 1.4 Flammability of plasticsThe flammability of base resins varies considerably, and can be characterised by the limiting oxygen index. The limiting oxygen index indicates the minimum percentage of oxygen required in the combustion atmosphere to sustain ignition and combustion. If the limiting oxygen index is 20% (atmospheric concentration) or lower, the resin will continue burning when ignited in the normal atmosphere. There is no simple relationship between a UL 94 rating and the oxygen index, but the oxygen index gives a broad indication of the flammability performance of the material. Oxygen indexes of a number of resins are shown in Table 1.1. The oxygen index of the resins may vary somewhat, and slightly different values may be found in different information sources. The oxygen index is also dependent on the addition of reinforcement materials. The addition of glass fibres, for instance, lowers the oxygen index of the plastic material, and requires a higher flame retardant loading to obtain a desired FR classification. Resins with a limiting oxygen index of more than about 30% are self-extinguishing, i.e. they can achieve a flame retardant grade without addition of flame retardant substances. Three of the resins included in Table 1.1 - polysulfone, polyaryletherketone and polyethersulfone - have such high oxygen indexes that flame retardant grades are achieved without addition of flame retardants. By mixing a resin with a low limiting oxygen index, e.g. polystyrene, with a resin with a higher index, e.g. polyphenylene, a copolymer with a higher limiting oxygen index than the pure polystyrene can be obtained. With a higher limiting oxygen index, the copolymer can meet a desired FR classification at lower FR loading, or with the use of less efficient flame retardants. Table 1.1 Limiting oxygen index of base resins [[7]]
* Oxygen indexes derived in [7] from Gareiß, B. 1995. Halogen-free flameproofing for engineering plastics. In: Polymers, BASF AG, Ludwigshafen (except for polyketone). ** Derived in [7] from Londa, M., Gingrich, R.P., Kormelink, H.G. & Proctor. M.G. 1995. Development of flame retardant aliphatic polyketone compounds. Shell Chemical Company, Houston.
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