LASER MARKING | TECHNOLOGY
Reaping the benefits of lasers
Additives, masterbatches and compounds formulated with laser decoration in mind are growing in
number.Peter Mapleston finds the choice of materials for laser welding is broadening, too
Laser marking of plastics offers numerous advan- tages compared to other decoration methods – it is resistant to abrasion, chemicals and weathering and can be applied to all sorts of surfaces, whether they be soft, hard, smooth, coarse, flat, stepped or curved. Laser technology also excels with its high adaptability, making it perfect for small batch sizes and rapidly changing layouts. As a consequence, many polymer and compound producers now include laser-markable – and also laser-weldable grades – in their line-ups. As far as the additives they employ to produce the desired effect are concerned, the technology now appears to quite mature. Applications, however, continue to in- crease and broaden. Evonik is among the leaders in this field,
offering laser-processable plastics (for decoration and for welding) as well as additive systems. The company points out that unmodified plastics do not absorb laser radiation in the region extending from the near ultraviolet to the near infrared. Conversion of laser energy into heat is therefore possible only if the polymer has been appropri- ately “laser sensitised” with a special additive. In the absence of laser additives, polymers can
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be processed only using far ultraviolet light, for example, with excimer lasers, and in far infrared light, for example, with CO2
lasers. Because the
Nd:YAG laser, which has a wavelength of 1064nm, is the most commonly used in practice, most moulding compounds for laser-marking are now formulated for the wavelength of this laser. Evonik’s High Performance Polymers Business Line has developed additives for laser marking that provide very high contrast: dark markings on light-coloured formulations and light markings on dark coloured and black products. Near-infrared absorbing additives designed especially for transparent plastics have also been developed by the company’s Inorganic Materials Business Unit. Evonik says that the transparent plastics that it
produces itself (Plexiglas PMMA and Trogamid polyamide) containing laser additives are distin- guished by their absolute colourlessness and very low haze. It attributes this to its nanoscale metal oxide additive technology, which, on account of the small particle size, does not scatter visible light. “The skill in the incorporation of the metal oxides lies in controlling their tendency to agglomeration and dispersing them as homogeneously as
February 2018 | COMPOUNDING WORLD 63
Main image: The QR code on this water bottle was created by laser marking using Buden- heim’s Budit L additive
PHOTO: BUDENHEIM
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