Recycling of thermoplastic UD tapes. A new measuring method for residual glass fibre length
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
European Regional Meeting of the Polymer Processing Society, PPS-2024
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
The sustainability of endless fibre-reinforced thermoplastic lightweight composites suffers from unsolved recycling issues. State of the art is incineration after product use. Obviously, an efficient and spiral mechanical recycling process, giving these composites a second life as high-quality short-fibre reinforced material, is needed.
The processing steps prior to molding a new high-quality component significantly affect fibre lengths and thus the component performance. These include milling of the composites, furthermore, melting and blending in a twin-screw or single screw-extruder as well as indirect or direct molding, the latter in an Injection-Molding-Compounder.
Optimizing each step needs a reliable, fast, and cheap method for measuring fibre length distribution. Thus we searched for optimal sampling, sample preparation, dilution, image acquisition and analysis algorithms.
We used shredded UD tapes and eliminated the polymer by TGA. A Keyence VHX-7000 digital microscope or a standard flatbed scanner were employed for image acquisition of residual fibre bundles. However, due to Keyence software limitations, the samples were downsized to representative sub-samples that avoid fibre overlap, as crossed fibres could not be separated correctly. Sampling method 1 involved extracting 4-5 mg of fibres using tweezers, which were then diluted in 400 ml deionised water, in contrast, method 2 included multiple dilutions of the fibre-water mixture. The fibre-water mixture was then poured into a petri dish, followed by two sample preparation steps. Finally, the automated software calculated the fibre lengths from the image data. Repeating each method for seven times proved high reproducibility.
We validated our method by measuring the same samples using standard equipment from Anton Paar and FASEP. The results were in good agreement. Our method is straightforward and low-cost.
Forschungs-