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Issue 01/2015

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bioplasticsMAGAZINE_1501

Automotive Biobased

Automotive Biobased thermoplastic composites for automotive interiors Biopolymer staple fibres/filaments (Bio) & industrial natural fibres (INF) Intimate fibre blending Blended sliver Warp knitting Composite yarn Composite fabric Yarn manufacturing Biosliver INFsliver Weaving Sliver blending Fig. 1: Processing routes for composite fabrics from Bio- and INF staple fibres [4] Increasing oil-shortages and rising oil prices, the environmental impact and the emission of greenhouse gases and the resulting climate change all lead to an enhanced preoccupation with the future of our oil based economy. Measures are taken to search for alternatives both in the field of energy resources and raw materials. Also in the world of the composites the search of renewable alternatives for both matrix polymers and fibre reinforcement is taking place. The vast majority of the European composite market (> 90 %) is still based on the traditional oil-based polymers and resins and glass-fibre or synthetic oil based fibre reinforcements. A smaller amount of Bio-composites has already entered the market. However, these biocomposites contain in general a small percentage (20 up to 50 weight %) of renewable materials. [1] Project Nature Wins The aim of CORNET Project Nature Wins was to tackle this exact challenge and develop composites from 100 % renewable raw materials. The project is a collaboration between three institutes; ITA (Germany), Centexbel (Belgium) and SLC-Lab (Belgium). The approach was to develop 100 % biobased composites with industrial natural fibres (INF) (flax, hemp) as reinforcements and biopolymer staple fibres (PLA) as matrix materials. The focus is on the establishment of a production route based on blending both matrix and reinforcement in the form of fibres and using compression moulding as composite formation process. [1] Fig. 2: Hybrid yarns and unidirectional composites Hybrid yarns from flax and PLA fibres Unidirectional bio-composites Natural fibre composites have shortcomings such as poor fibre-matrix adhesion and difficulty in impregnation owing to the difference in surface tension with polymer matrices. Furthermore, for achieving optimum mechanical properties, the orientation of the fibres in the composites is extremely important. [2, 3] In order to address these challenges, specific process routes for natural fibres were defined in the project Nature Wins. The component fibres are intimately blended and processed into various textiles structures (staple yarns, nonwovens, wovens) with varying structural geometries (isotropic, unidirectional (UD), bi-directional (Bi-D) using various technologies. 20 bioplastics MAGAZINE [01/15] Vol. 10

Automotive By: Sangeetha Ramaswamy, Bayram Aslan, Thomas Gries Institut für Textiltechnik der RWTH Aachen Aachen, Germany Mathieu Urbanus Centexbel Zwijnaarde, Belgium Linde De Vriese Sirris Leuven-Gent Composites Application Lab Heverlee, Belgium The structures are then developed into composites by compression molding. This involved melting the PLA fibres under high temperature and pressure. The molten PLA flows through the natural fibres and consolidates the fibres forming the matrix of the composite. With an intimate blending of the natural fibres with the PLA, the flow distance of the molten PLA reduces during compression. This leads to better impregnation and in turn improved mechanical properties of the composites. Textile Processing routes for Bio-composites The textile processing chain for woven and knitted fabrics for composite applications is illustrated in Fig. 1. Yarns are produced from natural fibre, PLA fibres and their blends using DREF (friction spinning, named after DR Ernst Fehrer) and rotor spinning techniques at ITA (Fig. 2). The yarns are then woven (Bi-D) or knitted (UD and Bi-D) to produce fabrics which have different orientations. For the development of staple yarns, flax fibres and PLA staple fibres (from Centexbel) were used to develop intimately blended yarns. The staple length used was 38 mm. A fibre volume fraction of 40 volume % of flax was used (corresponding to 50 weight %). The textile structures were consolidated into composites by SLC- Lab (Fig. 2). The process chain for developing blended nonwovens from natural fibres and PLA staple fibres is described in Fig. 3. For the nonwoven processing staple length of 60 mm was selected. The orientation of the fibres is controlled by using various laying technologies. For a random or isotropic orientation, air-lay technology is used. For a unidirectional orientation, carding technology is used. The structure of the composite can also be varied by intimately blending the fibres before forming the nonwovens or laying the individual natural fibre and PLA webs on each other. To consolidate the nonwoven webs, needle punching technology is used. Multiple layers of webs were needle punched together to obtain the required areal weight and thickness. The needle punched nonwovens were developed into composites at SLC-Lab using compression molding technology Biopolymer staple fibres/filaments (Bio) & Industrial natural fibres (INF) Intimate fibre blending UD and MD Bio-INF nonwoven Air-laid and roller card processing UD Bio nonwoven Pure Bio- and INF fibre UD and MD Bio-INF multilayed nonwoven UD INFnonwoven Fig. 3: Processing routes for non-wovens from Bio- and INF- staple fibres [4] bioplastics MAGAZINE [01/15] Vol. 10 21

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