JEC COMPOSITES MAGAZINE - Issue #72 - April/May 2012 - 66

natural fibre

High-performance natural fibre tape and spread tow fabric
A novel natural-fibre-reinforced thermoplastic prepreg tape has been developed to maximise the performance of sustainable biocomposites. The tape, initially based on flax and PP, has been converted into spread tow fabrics, which have very low crimp and provide high mechanical properties. The new materials are suitable for applications which require a combination of high performance, low weight and low environmental impact, such as automotive parts and sporting goods.

t is well known that natural fibres such as hemp and flax, which are derived from non-food crops, can be used as reinforcements to reduce the weight and environmental impact of composites, due to their low density and low carbon footprint compared to man-made fibres. On a stiffness-forweight basis, natural fibre composites can have equal or superior performance to glass fibre composites, while providing good thermal insulation and vibration damping properties. Therefore, there is considerable interest in using these materials in a wide range of sectors, especially in the automotive and other transportation industries. Natural fibres are discontinuous fibres that are most commonly available in the form of needle-punched mats with random fibre orientation, which only provide moderate reinforcing properties. To reach optimum performance levels and truly compete with glass fibre rovings and aligned textile reinforcements, natural fibres need to be converted into a continuous form with a high

degree of fibre alignment. For rapid processing of high-quality parts for the automotive sector, it is also desirable to combine natural fibres with a thermoplastic matrix in order to produce a preimpregnated, pre-consolidated material. A novel natural-fibre-reinforced thermoplastic prepreg tape has been developed with highly aligned fibres, which maximises the mechanical properties of the resulting biocomposites. The tape, which is currently based on flax and PP, was developed by Tilsatec Advanced Materials (UK) and Composites Evolution (UK). It is available as part of the Biotex family of high-performance natural composite materials. The tape has been used by Oxeon (Sweden) to produce a new TeXtreme® spread tow fabric variant based on natural fibres. This ultra-low-crimp fabric results in biocomposites with 40% higher stiffness than conventional woven materials and can significantly reduce the weight and environmental impact of composite parts.

availability in Europe. PP was chosen for the matrix because of its good balance of properties, processability and cost, which makes it an ideal candidate for automotive applications. In this technology, a commingled blend of flax and PP fibres is drafted to align the fibres in the machine direction. Then, the fibres are spread, heated and consolidated on a continuous basis to produce a prepreg tape. By changing the process parameters, it is possible to adjust the level of consolidation and therefore to produce tapes ranging from very flexible to very rigid. The Biotex tapes typically contain 40% flax by volume (50% by weight) although a range of fibre-matrix ratios are possible. Aside from the flax/PP version produced so far, it is also possible to use other natural fibres such as hemp, jute and bamboo, and

Tape development
In this case, flax fibre was selected as the reinforcement due to its good mechanical properties, high quality and good

66 jec composites magazine / No71 March 2012

JEC COMPOSITES MAGAZINE - Issue #72 - April/May 2012

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