Development of a bicomponent melt-spinning process for polymer optical fibres for automotive interior lighting

Polymer optical fibres (POFs) show a high potential for automotive interior lighting. The industrially used spinning process, which is optimised for POF used in data transmission, are over engineered. This leads to high costs which, among other things, hinder market growth. Melt-spun POFs have price advantages, but so far, their optical attenuation is too high and unstable. Therefore, the melt-spinning process needs to be adapted regarding its materials, machinery and process parameters to reduce the attenuation to below 2.3 dB/m while maintaining its low price and mechanical stability. Twelve research approaches regarding materials (core and cladding polymer), machinery (purifying, extruder screws and degassing, spinneret type), as well as processing (drying, process temperatures, cooling, diameter variations, drawing and annealing) are prioritised using a multi-criteria decision-making approach. This results in five series of melt-spinning trials which are mainly analysed for optical attenuation, but also for geometric variables and (knot) tenacity. Following the melt-spinning trials, weaving trials and a cost analysis for fibre production are carried out. The main objective is achieved with a POF suitable for automotive interior lighting with an attenuation of 1.54 dB/m. Regarding tenacity (knot tenacity) benchmark values of 9 cN/tex (8 cN/tex) are exceeded for post-draw ratios of 2 which leads to a weavability close to that of the benchmark POF. However, the drawing magnified diameter variations by a factor of 5 which leads to problems during processing and a reduction in strength, but also reveals further potential for minimising optical losses. Using an activity-based costing approach, an average potential reduction of 32 % in the self-costs for manufacturing POF using the melt-spinning process compared to the conventional process is revealed.