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issue 05/2021

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Highlights: Fibres, Textiles, Nonwovens Biocomposites Basics: CO2-based plastics

Biocomposites Automotive

Biocomposites Automotive composites from banana bast fibres Sudents Deepak Sundar Saravana Kumar, Maryam Sodagar and Balaji Subramanian, among others, of RWTH Aachen University, joined forces in 2020 to create a novel product from banana fibres. They founded team BioInterio, a student initiative with the aim of producing fully biobased and biodegradable composites for various applications. After winning the G-BiB 2020/2021 competition on a national level, team BioInterio successfully took part in the international final at the beginning of 2021, competing against teams from the United Kingdom and Finland. In addition, they also won the Biobased Innovation Student Challenge Europe on the National level and are part of the Chemstars community as well as the RWTH Ideation Program. Using feedback from these experiences, they successfully applied for and were recently granted the NRW Gründerstipendium, to take their ideas to the next level. The product team BioInterio aims to produce is a composite made from hybrid nonwovens, consisting of banana fibres as well as biobased and biodegradable polyesters. While polyester fibres are already used as matrix polymers for composite applications, using banana fibres as a reinforcing fibre is a novel approach. Other than abacá, which also belongs to the plant family of banana plants, the banana fibres which team BioInterio used were not cultivated for their fibre content but as a food source. As such, once bananas are harvested the plants serve no further purpose. Current procedures to deal with what is essentially considered a waste product, include producing fishing nets and ship ropes due to high saltwater resistance, or simply burning down the remaining stems of the plants if the field space is needed. The latter has the advantage of acting as soil fertilization, but emits carbon dioxide into the atmosphere and burns valuable biomass that would not need further water or maintenance to be harvestable. If the stems are harvested the retting can be done by chemical means or mechanical separation. The sale of banana fibres also provides an additional source of income for local farmers. While abacá fibre from similar plants is gathered from leaves, the banana fibres used by BioInterio were bast fibres sourced from the stem of the plant. As such they possess all the advantages of other common natural fibres such as flax and hemp (renewable, biodegradable, high specific strength and modulus, low density, excellent dampening properties) and can be processed in a similar way. One further advantage is a 1.5 times lower cost compared to other fibres such as flax and hemp. The students of team BioInterio sourced banana fibres of varying hoarseness from Indian locals and processed them at the Institut of Textile Technology of RWTH Aachen University. While working at the institute, they had full access to machinery and expertise in the nonwoven and composite production as well as characterization of both. Using these resources, hybrid nonwovens could be produced on laboratory scale equipment (see Figure 1 for a process scheme) and thermoformed into test specimens as well as a prototype glove compartment lid for the automotive industry, as depicted in Figure 2. Even without optimization, the composite showed an even distribution of fibre and matrix and a smooth surface quality. The first characterization steps included an analysis of Figure 1: Process chain for the production of banana bast fibre polyester composites at ITA primary material (banana fibre & PLA filament) hybrid nonwoven production mechanical bonding of nonwovens rough cut component consolidation 40 bioplastics MAGAZINE [05/21] Vol. 16

By: Anne Hennig, Lars Wollert, Frederik Cloppenburg, Lennart Jacobsen, Thomas Gries Institute of Textile Technology of RWTH Aachen University Maryam Sodagar, Deepak Sundar Saravana Kumar, Balaji Subramanian, Christoph Greb BioInterio All: Aachen, Germany Biocomposites thermal stability via thermogravimetry. Results showed the main degradation step beginning at an onset temperature of 288 °C with a second, smaller step at around 430 °C. The material showed excellent thermal stability up to these temperatures and, as such, is suitable to be used as a composite in automotive interior applications. Additionally, mechanical properties were evaluated via tensile and bending tests. In bending tests, based on the DIN EN ISO 14125 standard, a bending strength of 23 MPa was achieved even without optimization of the materials and processes, which is only slightly below the requirements for the automotive industry. In the tensile test based on the DIN EN ISO 527-4 standard, a tensile strength of 10 MPa was achieved, also without prior optimization. Results are depicted in Figure 3. insulation viable. A big share of the global natural fibre market is the supply of the automotive natural fibre market. Similarly, the composite market makes up a big portion of the automotive door panel market. As such, both are the priority target markets for BioInterio, with the biggest selling point being a reduced price for natural reinforcing fibres while keeping their advantages. The next step is the founding of BioInterio as a company and the start of pilot production in 2022. Commercial-scale production is scheduled for 2023. Currently, the aim of BioInterio is the further improvement of mechanical properties of the composite product to make it a viable option for crash-relevant parts in the automotive industry, such as door panels. Strategies to achieve this involve the usage of alternative processing parameters for both the hybrid nonwoven production and consolidation, as well as blending banana fibres with different natural fibres such as flax and hemp to create a more even composite. In the future, such banana fibre composites can also be used as seat shells for the automotive industry. A usage in furniture and sports applications would allow combining the excellent mechanical properties with new surface looks, leaving natural fibre surfaces visible to the end customer. The dampening qualities also make applications in acoustic Figure 2: Glove box cover produced from banana bast fibre polyester composites Figure 3: Bending stress and tensile strength of banana bast fibre polyester composites without prior optimization 30 12 Bending test according to DIN EN ISO 14125 bending stress in MPa 25 20 15 10 5 10 8 6 4 2 tensile strength in MPa 1 kN XForce HP force transducer 0.5 mm/min testing speed Tensile test according to DIN EN ISO 527-4 100 kN Xforce K force transducer 2 mm/min testing speed F F 0 bending stress tensile strength 0 F bioplastics MAGAZINE [05/21] Vol. 16 41

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