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Issue 04/2019

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Highlights: Blowmoulding Composites Basics: Home Composting Cover Story: Cove PHA Bottles

Biocomposites Figure 3:

Biocomposites Figure 3: Comparison of the new compounds with commercially available wood filamentswires. Shown are the Young’s moduli, the tensile strength and the unnotched Charpy impact strength of the new 20% wood fibre/80% polymer compound 1 and one low and one high priced 3D-printing filamentwire Elastic modulus in MPa 3000 2500 2000 1500 1000 500 Tensile strength in MPa 40 30 20 10 Charpy impact strength in k J/m 2 20 15 10 5 0 0 0 Reference 1 - low price Reference 2 - high price 20 % wood fibre 1 Reference 1 - low price Reference 2 - high price 20 % wood fibre 1 Reference 1 - low price Reference 2 - high price 20 % wood fibre 1 Advantages of the innovative compound development There are various advantages to using fibre-reinforced biobased compounds for 3D-printing, including: Improvement in the FDM process: • An impact modifier of the Forbio series (company Linotech GmbH & Co.KG, Forst, Germany) was used in combination with PLA and 20% wood fibres increased the bendability of the thermoplastic wire, which resulted in a lower break tendency when using small coils;; • The compounding systems used allows both small batch size production as well as mass production for individual material solutions. Mechanical properties: • The mechanical performance (Young’s modulus, ultimate strain, Charpy impact strength) of the specimens is adjustable over a broad range while the processability for additive manufacturing remains constant. • Equal or better mechanical properties compared with commercially available wood containing thermoplastic wires. Thermal properties: • Optimized heat distortion behaviour compared to pure PLA could be determined. • The processing temperatures are relatively low (180 - 190 °C), to avoid degradation of natural fibres. Post processing optimisation: • In contrast to using only pure polymers, products of the wood fibre-reinforced compounds can be sanded and sawed after being printed. Energy consumption: • Lower processing temperatures during the printing process, compared to pure polymers with comparable mechanical properties (e.g. ABS). Aesthetic properties: • The printed specimens feature an attractive, natural look. A large range of advantages could be demonstrated, but there is still scope for optimisation. While the thermoplastic wires produced can be printed by professional and home user 3D-printers, oozing is still a problem, compared to pure PLA. The experiments showed a correlation between the absorption of water in the wood fibre-reinforced thermoplastic wire and the oozing behaviour. This behaviour can be decreased using smaller wood fibres. Ongoing research is focusing on this topic. References DIN EN ISO 527 Teil 2 1993 einschließlich Corr 1: 1994 Kunststoffe – Bestimmung der Zugeigenschaften – Teil 2: Prüfbedingungen für Formund Extrusionsmassen DIN EN ISO 179 Teil 1 2010. Kunststoffe – Bestimmung der Charpy-Schlageigenschaften – Teil 1: Nicht instrumentierte Schlagzähigkeitsprüfung www.hs-bremen.de | www.ist-ficotex.de | www.nhlstenden.com | www.3-n.info Acknowledgement The authors acknowledge the funding agencies for the possibility to work on the shown topics within the cross-border project „Bioeconomy in the non-food sector“ (http://www.bioeco-edr.eu), funded within the programme INTERREG V A-Germany – Netherlands by the European Fond for Regional development (EFRE) co-financed by the land Lower-Saxony, the Dutch ministry of economics and the Dutch provinces Drenthe, Flevoland, Fryslân, Gelderland, Groningen, Noord-Brabant und Overijssel. 32 bioplastics MAGAZINE [04/19] Vol. 14

Biocomposites Natural fibres How to enable their application for structural composite parts T he production of conventional reinforcement materials for structural composites requires large amounts of energy resulting in a high environmental impact. A promising approach to overcome this problem lies in the application of natural fibres. At ITA and PuK, such an approach is currently investigated. Reinforcement fabrics for mechanically highly stressed composite parts are usually made of conventional reinforcement fibre materials such as glass, carbon or aramid. The production of these materials requires a high amount of energy and therefore leads to high CO 2 emissions when using fossil fuels. A promising approach to reducing the environmental impact lies in the use of renewable resources. Such resources can be natural fibres, which require significantly less energy in their production. Compared to glass fibre reinforced plastics (GFRP), natural fibre reinforced plastics (NFRP) can save up to 40 % energy and 30 % CO 2 emissions in their production. Due to their low density, they are highly suitable as reinforcing materials in thermoplastic or thermoset fibre composites. NFRP are already used on a large scale for non-structural components with low requirements in terms of mechanical properties (EU 2015: approx. 120.000 t). However, they are currently rarely used for structural applications. This is mainly due to the fact that the mechanical potential of the fibres has not been fully exploited yet. Especially the twisting of the fibres during the spinning of yarns reduces the intrinsic mechanical properties of the natural fibres and lowers the fibre volume content and impregnation behavior of the reinforcement fabrics. In addition, some properties, such as thermal stability and moisture absorbtion, reduce their potential for industrial application aswell. Experiments on a laboratory scale at ITA have shown that NFRP reinforced with fully oriented flax fibres show comparable specific mechanical properties to GFRP. The challenge lies in transfering these results to an industrial scale. At ITA and PuK, a novel approach based on the direct processing of untwisted flax slivers to produce non-crimp fabrics (NCF) is investigated. Due to the saved spinning process, the fibres can be fully aligned, which increases the mechanical properties of the composite material and at the same time reduces production costs. However, the finite length of the natural fibres proves to be problematic. The slivers show a limited cohesion, which makes feeding at conventional NCF production systems, especially at high production speeds, difficult. In order to solve this issue, consolidation and transport mechanisms for untwisted flax slivers were investigated at ITA. Based on the results, a novel feeding and weft insertion device was developed and integrated into a warp knitting machine with multiaxial weft insertion. The cohesion of the slivers during the transport is ensured using a false twist mechanism. The slivers are temporarily twisted in particularly critical sections of the feeding line. The cohesion of the slivers is thus increased and allows high production speeds. With the modified technology, flax noncrimp fabrics (NCF) with fully oriented layers (e.g. ±45°) can be produced. Compared to NCF made from flax yarns, the new fabrics show a significantly higher homogeneity of fibre distribution without gaps at comparable area weights (see Figure 1). The extent to which the mechanical properties of NFRP can be improved using the new NCF is currently being investigated at PuK. In addition to composite testing (tensile, bending and impact strength), investigations are carried out with regard to the compaction, permeability and resin flow behaviours of the new fabrics. The results will be benchmarked against currently available materials. It is assumed that the mechanical properties will be significantly improved due to higher fibre orientation and fibre volume content. In addition, the untwisted fibers will presumably allow better drapability and much faster impregnation than conventional fabrics. The latter would significantly reduce production times in component manufacture. If proof can be provided, the project results are to be transferred to industry. www.ita.rwth-aachen.de | www.puk.tu-clausthal.de Acknowledgments The IGF-project 19400 N (HyPer-NFK) of the Forschungskoratorium Textil e.V., Berlin is financed through the AiF from funds of the Federal Ministry of Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag. Figure 2: Unprocessed flax sliver and flax non-crimp fabric By: Carsten Uthemann, Research Associate Alexander Janßen, Head of Division Staple Fibre Technologies ITA - Institut für Textiltechnik, RWTH Aachen University Aachen (Germany) Alexej Kusmin, Research Associate Leif Steuernagel, Head of Division Renewable Materials PuK, Clausthal University of Technology Clausthal-Zellerfeld (Germany) Figure 1: Comparison of non-crimp fabrics produced from flax yarns (top) and flax slivers (bottom) bioplastics MAGAZINE [04/19] Vol. 14 33

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