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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Range of infra-red emitters
Keywords Heraeus Noblelight, Infra-red, Heating, Emissions, Plastics
Heraeus Noblelight of Bromborough, Wirral, can now offer a new wide range of infra-red emitters, which have been specially developed for applications in the plastics industry. The emitters are offered with different emission spectra, with different outputs and in different shapes and sizes, so that they can be precisely matched to the requirements of individual heating processes. This reportedly allows faster response times, higher productivity and significant energy savings.
Infra-red heating relies on the fact that specific components of the emitted infra-red radiation spectrum coincide with the wave length of the molecular oscillation in the material to be heated. Radiation at these wavelengths is absorbed by the material and this absorption involves transferring energy to the appropriate molecules so that the material is heated. Plastics absorb infra-red radiation predominantly in the wavelength range above 2µm. Specifically, C-H bonds absorb wavelengths between 3.2 and 3.5µm, while polyethylene and polyvinylchloride exhibit strong infrared absorption at wavelengths between 2.5 and 4.0µm.
Material thickness also affects the efficiency of absorption, and hence heating. Thin materials and foils are difficult to heat with short wave radiation (below 2µm), as only a small component of the radiation matches the absorption spectrum of the material. However, medium wave infra-red is absorbed more strongly and provides faster heating for the same power output.
Alternatively, because of its low absorption, short wave infra-red penetrates deeper into a material and provides uniform volumetric heating while medium wave is absorbed rapidly in the material outer layer and so predominantly heats only the material surface.
As well as matching the emitter spectrum to suit the particular application, Heraeus can also provide emitters in various shapes and configurations to ensure that the emitted infra-red is precisely targeted. Carbon bulb emitters direct energy at specific areas, small surfaces and surfaces which are curved at different angles. For larger surfaces, emitter fields can be built to match the surfaces to be formed, such as in deep drawing. Circular Omega emitters, with an outside diameter of 45mm to 160mm, can be used for the heating of tubes, billets and similar shapes. Contour emitters can be precisely formed to match products whose surface areas or edges are to be heated.
Consequently, by a combination of the correct emission spectrum selection and an emitter shape which allows precisely targeted heating, the new range of Heraeus emitters can reportedly be used for a wide range of plastics processing operations. These are said to include surface heating for adhesion processes or for drying, surface heating of foils and thin films and uniform volumetric heating of large components, such as billets and plates.
Details available from: Heraeus Noblelight Ltd. Tel: + 44 (0)1 51 343 0545; Fax: + 44 (0)151 343 9883.