JEC COMPOSITES MAGAZINE - Issue #37 - December 2007 - 44

FEATURE “Biocomposites” Flax-epoxy prepregs leading the race No one can deny the advantages of natural fibres, and yet they are rarely used in composite materials. The Lineo Company is now offering prepregs reinforced with natural flax fibres. Recognized properties FRANCOIS VANFLETEREN, PRESIDENT LINEO The mechanical properties of flax fibre are similar to those of standard glass fibre. Flax has other advantages, however. It is lighter than carbon and has a density of 1.45 (Table I). Table I: Density comparison Material water flax carbon glass steel P eople around the world have been using flax fibre as a textile fibre for thousands of years. Nowadays, composites constitute a new outlet for flax – one that is equally as interesting as it is unknown to most people. Flax fibres have been used in composites for a number of years to improve materials by their insulating properties and low weight, but this has involved very little added value. In such applications, short flax fibres must compete in the market with other fibres such as kenaf, jute and sisal. But there is another potential outlet that could be sustainable for long flax fibres, in parallel with the textile industry, by using them as reinforcement in composite materials, just like glass or carbon fibres. This utilization would be based on the intrinsic physical properties of flax fibre, and therefore would exclude any competition with other natural fibres. Density 1 .45 1.7 2.54 7.8 More information Lineo: the fruit of partnership Lineo was created by four companies: - IPA, a manufacturer of carbon-based composite parts, - Stanislas Cock, a flax spinning mill, - Linière de Saint Martin, a flax fibre preparing mill, - Teillage de Saint Martin, a flax cultivator and fibre extraction mill. The joint project consisted in developing a process that would make it possible to use natural flax fibres as reinforcement in composite structures. Following research by IPA and Stanislas Cock, a patent was filed to protect the flax-fibre sizing process and allow its use in high-performance composites. Lineo offers an innovative product in a market that is dominated by glass and carbon fibres. Like natural fibres in general, it also has vibration-absorbing properties that are due to the links between cellulose and hemicellulose chains – low-energy bonds that are known as the Van der Waals force. During vibration, these contact bonds break easily, allowing the molecules to move slightly. Thanks to this potential for movement, the fibre is able to absorb the vibrations. There are many similarities between flax and carbon fibres (such as a coefficient of expansion that is practically zero and an elongation at break of about 1.5%), so it is possible to make high-performance hybrid composite parts that are reinforced with both flax and carbon (Figure 1). Water has a density of 1, corresponding to the weight in kilograms of a litre of water. Flax fibre is lighter than steel, and lighter even than carbon and glass fibre. Fig. I: hybrid composite reinforced with flax and carbon fibres A patented process One of the founders of Lineo developed and patented a process to impregnate natural flax fibres with thermosetting resins. The company now has exclusive licence status under the patent to manufacture and market flax-fibre-reinforced prepreg materials. The process appears to solve all the problems confronting manufacturers who have tried to introduce flax into composites. JEC Composites Magazine / No37 December 2007

JEC COMPOSITES MAGAZINE - Issue #37 - December 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #37 - December 2007