JEC COMPOSITES MAGAZINE - Issue #55 - February/March 2010 - 31

Weaving High-performance biocomposites: novel aligned natural fibre reinforcements A new family of high-performance natural fibre reinforcements have been developed using a novel ‘twistless’ yarn technology. These sustainable materials have been designed to overcome the limitations of existing natural fibre products and have been launched commercially. reinforced composites suitable for use in structural or semistructural applications. Following successful development, the materials have been launched commercially with the name Biotex and are available in flax, commingled flax/PP and commingled flax/PLA versions. DR BRENDON WEAGER, TECHNICAL MANAGER, COMPOSITES EVOLUTION LTD. Material development T here is currently a dramatic surge in interest in environmentally sound materials and technologies in virtually every industrial sector and global region and composites derived from natural, renewable resources have a significant role to play. Natural fibres such as hemp, flax and wood are already used in the automotive industry to reduce weight, cost and environmental impact. In fact, on a stiffness-for-weight basis, natural fibres can have equal or superior properties to glass fibres. The natural fibres currently used in composites tend to be short and randomly oriented, which means the composite mechanical properties are relatively low and the applications are limited to nonstructural parts. It is well-known that fibres provide the highest strength and stiffness when they are continuous and aligned in the direction of applied load. Natural fibres are naturally discontinuous and conventional spun yarns tend to be highly twisted which leads to fibre misalignment and poor wet-out. An exciting recent advancement has been a new family of aligned natural fibre reinforcements developed by a UK-based consortium, which has overcome these issues by using novel ‘twistless’ yarns. The Combine project, co-funded by the UK Technology Strategy Board, was initiated to develop higher performance natural fibre- Hemp and flax fibres were selected because they have good mechanical properties and can be grown in European climates. The fibres have been improved by developing the agronomy, retting (where bacteria loosen the fibres in the crop stem) and fibre extraction processes, and investigating treatments to improve the fibre-matrix bonding. The work initially focussed on thermoplastic matrix polymers including polypropylene (PP) and polylactic acid (PLA), a biopolymer from corn starch. In particular, the effects of polymer viscosity and compatibilising additives on consolidation and fibre-matrix bonding were studied. Fig. 1: Weaving novel “twistless” yarns In brief Biotex high-performance natural composites: - Flax, commingled flax/PP and commingled flax/PLA - Yarns, fabrics and pre-consolidated sheets - “Twistless” yarn technology - Sustainability, performance and processability Natural fibre yarns have been developed using novel ‘twistless’ spinning techniques thereby producing continuous reinforcements with straight fibres, good mechanical properties and good wet-out and impregnation. Woven fabrics were produced from the yarns in a range of weave styles designed to minimise crimp and maximise drape (Figure 1). Yarns and fabrics were produced from flax and hemp to be suitable for reinforcing thermosetting resins such as unsaturated polyester (UP), epoxy or bioresins. In addition, novel commingled yarns and fabrics containing blends of natural fibres No55 February - March 2010 / jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #55 - February/March 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #55 - February/March 2010