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industries electrical | SMC and BMC for electrical and electronic applications |
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With experience of more than 60 years composite materials have reached a peak performance in the area of electrical and electronic applications. Menzolit SMC and BMC have outstanding properties to match the requirements of electrical and electronical applications. To outline only the major advantage in this chapter a short overview is presented to line out how efficient Menzolit SMC and BMC are for the compression and injection moulded parts. Electrical properties of SMC / BMC partsNatural InsulatorsMenzolit SMC and BMC as thermoset compounds show intrinsic insulating properties. Acc. to IEC 60093:1980-01: Specific volume resistance is 1012 to 1014 Wcm-1. Specially formulated Menzolit SMC 2600 for explosion-proof applications shows specific volume resistance <106 Wcm-1. IEC 60250:1969-01 dielectric dissipation factor tan d is 0.01 and is relatively stable across a wide range of temperatures and frequencies. The relative dielectric constant is low, at a test frequency of 1 MHz. IEC 60243 [VDE 0303 Part 21]: 1999-03 electrical strength is 17 kV/mm to 19 kV/mm. IEC 60112 (VDE 0303 Part 1): 1984-06 (comparative tracking index) SMC / BMC match the CTI 600 level and are much better than engineering thermoplastics. The overview of the electrical engineering properties demonstrates that SMC / BMC are ideal for the insulation of electrical systems. UL746 A: Polymeric materials short-term property evaluation MenzolitSMC and BMC can easily be adjusted to be classified in PLC 0. UL746 B: Polymeric materials long term property evaluation SMC and BMC are an excellent choice for electrical and electronical applications regarding the mechanical properties. SMC and BMC parts fulfil the RTI 150 rating.  Additional benefits of SMC / BMCSMC / BMC can be customized for discharging of electrical charges in ex-proof environments.This areas are classified in:
There are many standards for explosion protected equipment:
The hazardous environments of ex-proof applications include often temperature loads, outdoor exposure, rough weather conditions and chemical attack. Off-shore exploration rigs and mining environments are the most challenging examples. Most common applications are ex-proof lamp housings made of SMC, terminal boxes, plugs, sockets and of course ex-proof components for distribution of energy. 
General benefitsOther requirements, mainly mechanical, are relative to the type of application. For example, temperature resistance is important, and SMC compounds have been successfully used for cable distribution cabinets in outdoor applications. SMC is extremely resistant to weathering and low temperatures – even down to –40°C where no embrittling can be observed !A further benefit for housings is dimensional stability. SMC can resist heat generated by electrical systems and to long term mechanical stresses. The increasingly complex and compact design of the circuit beakers requires ever-higher levels of dimensional stability and performance. Long glass fibres and 3-dimensional crosslinked molecular structure of UP resin enable SMC / BMC compounds to have significant reserves to serve even at temperatures of 200 °C or more. General benefits. Functional integration by the embedment of metalsComposites such as SMC / BMC enable the conductivity of metals to be combined with the insulating capabilities of plastics.Obstacles to achieving this kind of compatible connection are frequently high moulding shrinkage of plastics and the differences in CTE. Both factors mean high internal stresses around the embedded metals avoiding build up of cracks. Such problems are not encountered with SMC / BMC due to their moderate thermal expansion. By reducing the number of components and integrating numerous functions in one component, it is therefore possible to embed current-carrying copper conductors – for example - in SMC or BMC for instance for disconnection switchgears. SMC/BMC – ideal materials for electrical engineeringIn summary, the combination of favourable semi-finished product costs, good electrical insulation properties, the ability to withstand continuous mechanical stress(particularly in heat), and high functional integration, enable SMC and BMC to compete very favourably with engineering thermoplastics. Frequently underestimated by electrical component designers, these materials offer economical and high performance solutions to complex electrical engineering challenges. More intricate and compact designs, constantly increasing material requirements and cost constraints, will make the use of SMC / BMC even more compelling in the future. For these reasons, many OEMs are already collaborating closely with manufacturers in the further development of these important materials. Maximum fire protection – and environmentally friendlyStatistics produced by the Berlin Fire Brigade, show that electricity is the second most frequent fire ignition source. In 31 % of all cases, a synthetic material is the first to be ignited. Consequently, the plastics chosen for the insulation of electrical currents should be as difficult to ignite as possible and must not help to propagate the fire.Flame retardants are often used to achieve this. While most of plastics demand chlorinated or brominated flame retardants, SMC and BMC provide the same properties using environmental friendly mineral compounds. The EU intends to prohibit the use of several brominated flame retardants by 2008 in a directive on the restriction of hazardous materials in electrical equipment. These flame retardants also have the disadvantage that they create a large amount of smoke, and it is smoke that tends to be the main cause of damage and fatalities in fire situations. The fumes not only hinder fire fighting, they are also suffocating for humans and corrosive, thus causing extensive damage to machines and equipment. Naturally occurring mineral fillers are an environmentally preferable alternative. However, they cannot be added to viscous thermoplastic melts in sufficient quantities and are rarely able to withstand the high processing temperatures used with thermoplastics. On the other hand, low-viscosity UP resins may be filled with naturally occurring aluminium trihydroxide, for example, and thus provide excellent protection against ignition and flame propagation. SMC/BMC can therefore easily meet the requirements in the above-mentioned EU Directive. Probably the most common test in the world used to evaluate the fire behaviour of plastics is the determination of the oxygen index in accordance with DIN EN ISO 4589: 1999-09 [20]. In this test, a plastic sample section is ignited and examined to determine the oxygen / nitrogen mixture at which the flame continues to burn. An oxygen content of 21 % represents normal atmospheric conditions. Therefore, the more difficult to ignite the plastic is, the higher the oxygen concentration has to be set. Specific SMC formulations have a limiting oxygen index of > 90 % which represents excellent flame resistance.  Menzolit SMC and BMC can be adjusted to meet all levels of fire retardancy and smoke emission.
* = NF = non flamming mode / F = flamming mode Comparison of materials used in electrical and electronical applications
Mechanical properties of new part versus outdoor exposed parts SMC and BMC are an excellent choice for electrical and electronical applications regarding the mechanical properties. SMC and BMC parts fulfil the RTI 150 rating as described by UL 746B. Productlist
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