116 REPORTS AND STUDIES Hohenstein Institute New absorber systems to improve the quality of laser welded seams on technical textiles As part of a research project (AiF-No. 17031 N) "Absorber systems for laser welding of textiles", scientists at the Hohenstein Institute are currently working with colleagues from the German Wool Research Institute in Aachen on developing new infrared absorber systems to improve the quality of laser welded seams, both mechanically and visually. This should enable the laser welding of textiles, which is an alternative and promising but still new technique for making seams, to be introduced more widely. Especially in the production of technical and medical textiles, this is expected to bring about a significant improvement in quality compared with conventional techniques. The laser welding of textiles has many advantages compared with traditional stitching with needle and thread. The biggest improvements in product quality can be achieved in the processing of large-scale technical textiles. The seams produced by welding are flat, flexible, completely sealed against liquids and gases and have impressive tensile strength. The normal seam defects can be avoided and the quality of the welding process can be automatically monitored online. These properties are demanded in many technical fields such as medical textiles, protective clothing, textiles for vehicle interiors, furniture manufacture and outdoor products. The new process would minimise the currently very time-consuming testing of the quality of the seams which has to be carried out during and after the manufacturing process. One of the problems inherent in the still relatively new and little used method involving an infrared laser is that only a few textiles, made of thermoplastic fibres, absorb laser radiation in the near-infrared range. This means that, with many textiles, absorbers have to be used which are specifically designed to absorb the infrared light. However, these substances can cause discolouring or colour changes round the seams. This characteristic makes it more difficult to use laser welding, especially on light-coloured or transparent textiles. Now, as part of this ongoing research project, new absorber systems are to be developed and systematically studied. The new formulations need to be easy to use and economical on materials, compatible with the textile material and to meet all the preferred requirements as far as possible. Especially on light- coloured and transparent textiles, they should result in seams that are perfect visually and mechanically, and are highly fit for purpose. Furthermore, the variable parameters for laser welding such as temperature, speed and pressure can be adapted to suit the absorbers. This will enable manufacturing companies to use the process directly for their own materials and product range. The new joining technique will be suitable both for individual items and for highly automated mass production. Reducing the number of process stages and increasing the process quality will enable small and medium-sized companies to boost their output and give them a competitive advantage over companies using conventional textile joining techniques. PPE: MATERIALS, MACHINERY AND TECHNIQUES FOR THEIR PRODUCTION