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Analysis for Bromine in Electronic Parts Encl. CMemo on the Project: Analysis for Bromine in Electronic PartsPrepared by Nils H. Nilsson, Environmental and Waste Technology, Danish Technological Institute, for Ivan Christensen, Chemical Technology, Danish Technological Institute Introduction The primary aim of the project was to determine to what extent brominated flame retardants are found in household appliances on the Danish market. The present memo assesses the possibility of other bromine compounds than brominated flame retardants being present in the plastic parts of the household appliances than the brominated additives added to the plastics to have a fire retardant effect. Overall conclusion On the basis of the Institute’s collected knowledge on plastic materials and a brief literary survey of additives for plastics it seems to be extremely unlikely that other brominated compounds have been added to the plastics of the household appliances than the bromine-based flame retardants and under no circumstances in concentrations of an order corresponding to that of the fire retardants. In the first place, the bromine compounds are rather expensive as compared to the corresponding chlorinated compounds, secondly, no examples of commercially offered or otherwise used additives in the form of bromine compounds for plastics other than the brominated flame retardants have been found in the handbooks and literature studied. The reason why the bromine-based flame retardants are used to such an extent is that by addition of a comparatively small amount of the bromine-based flame retardants a fire retardant effect is achieved so that the plastics can fulfil the so-called UL-requirements or other standardized fire classifications. However, it must be added that the bromine-based flame retardants in large concentrations may function as plasticizers in the plastics if the solubility parameters make it possible. Otherwise the flame retardant must be regarded as a filler. Furthermore, it should be mentioned that in principle it is possible to build bromine-substituted monomers into the plastic polymer with the same purpose, viz. to reduce the combustibility of the plastics. It depends entirely on the type of plastics if this is a realistic possibility. Another possibility is to brominate the polymer after the polymerization process. This is hardly very realistic. Reactive flame retardants are primarily used in connection with thermoset, for instance polyurethane polymers and epoxy polymers. These plastic types are not assessed to be used in household appliances to any appreciable extent. However, thermoplastic polyurethane types may form part of household appliances. It should be added that reference1 states the possibility of building hologen-containing monomers into ABS (acrylonitril-butadiene-styrene plastics). Both chlorine and bromine belong to the halogens. Basis of assessment The references state the literature that has been used as the basis for the conclusion. At the same time it can be mentioned that through almost 20 years’ work with the chemistry, physics and technology of plastics the undersigned has not come across literature dealing with other bromine compounds added to plastics in relation to the plastic types used commercially in electric and electronic appliances, including household appliances, than bromine compounds with fire retardant properties. Household appliances Household appliances comprise first and foremost electric articles such as vacuum cleaners, hair dryers, curling irons, toasters, coffee machines, hot water boilers, mixers, blenders and other electric types of mixing equipment as well as shavers and massage apparatuses. Types of plastics used for household appliances A number of different types of plastics are used in electric household appliances. Whether the plastics is fire retardant or not depends on the location of the plastics in relation to the electric parts of the appliance, how high and critical the temperature is at maximum load, and the legislative requirements applying to electric articles /electronics. The most frequently used plastic types for household appliances are polyethylene, polypropylene, acrylonitril butadiene styrene (ABS), polyester types (PBT, PET), polycarbonate (PC), polyamides (PA 6, PA 66), polysulfone (PSU), polyphenylene oxide (PPO), polyether sulfone (PES) and phenol plastics. The last type is a thermoset as compared to the rest which are all thermoplastic types. The choice of plastic type depends on the kind of mechanical properties essential to the perfect functioning of the household appliance, the temperature to which it is exposed, electric properties (insulating, antistatic), possible demands in relation to food contact, etc. Fibres or fillers may often be added to the plastics. These may both contribute to strengthening the plastics, but also to reducing the combustibility of the plastics. Polyethylene (HDPE) and polypropylene (PP) are the less expensive of the plastic types. However, they are also those of the above-mentioned plastic types with the lowest melting interval/softening point, and therefore, there is a limit to the temperature to which they can be exposed. PBT and PET are much used in electric household appliances, among other things because of their high softening temperature and a relatively favourable price of the raw material. Fire retardants There are brominated fire retardants reacting with the plastics and therefore chemically bound in the plastics as well as fire retardants not chemically bound. Antimony trioxide, which appears on the National Agency of Environmental Protection’s list of undesired substances, is often used together with brominated flame retardants as there is a synergistic effect. The reactive types of brominated flame retardants are used in the thermoset types unsaturated polyester, polyurethane and epoxy. These plastic types are not considered of great use in household appliances. However, epoxy is applied for printed circuit boards. The table overleaf shows examples of the concentrations of flame retardants used in the different types of thermoplastics in order to be able to fulfil the UL 94 fire klassification (UL = Underwriters’ Laboratories). The informa- tion comes from reference 7. Owing to their chemical lay-up and very high melting temperature, the polysulfone types have low ignition properties and flame spread in the case of fire. Therefore, there is little or no need for adding flame retardants to these types. Concentration of flame retardants in thermoplastic types
flame retardant is used. Thus, the quantity of brominated flame retardant can be limited, reducing the risk of changing the mechanical properties of the plastics in a negative direction. Many of the plastic types are also available with glass fibre reinforcement or addition of small glass balls, which enables a change of the rigidity of the material and reduces the quantity of plastics in the construction, making it less expensive. References
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