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In this article, our intention is to run the rule over the ways in which plant fibres are used in Europe in general and in France in particular, to highlight some of the new uses for plant fibres in industry and to draw some conclusions about the development prospects for these new industrial channels.
(Published on January-February 2009 – JEC Magazine #46)
HILAIRE BEWA, ENGINEER, DERRME/ADEME BIORESOURCE DEPARTMENT
The traditional sectors of application for plant fibres in Europe are the textile and paper industries. Over the last decade or so, the economic context (reduced cost of raw materials) and the environmental context (reducing the impact of industrial products on the environment) have encouraged the emergence of new sectors. Indeed, across the board, plant fibres are increasingly in vogue for their many environmental, technical, economic and health benefits that the various branches of industry could leverage: renewable raw materials, biodegradability and neutral carbon balance, low density, energy efficiency, flexibility, low-cost, reduced or zero allergenic or health incidence for production line workers, etc.
In specific applications, the intrinsic characteristics of plant fibres allow manufacturers to obtain materials offering superior technical performance to that of traditional materials. Today, the use of plant fibres is finding particular favour in two main industrial sectors: the automotive and the building industries.
Plant fibre production in Europe and in France
In Europe, the two main types of fibre produced are flax and hemp. According to an Ernst & Young study carried out in 2005 on behalf of the French energy conservation agency ADEME, France is the world's number one producer of scutched flax (113,000 metric tons (MT) in 2003) and the third behind Russia and China in terms of land use (76,600 ha). France's production, which accounts for ¾ of all European production, endows it with unique potential for this segment of industry. The other European producers of note are Belgium (29,000 MT and 19,250 ha) and the Netherlands (6,900 MT and 4,600 ha).
As for hemp, the annual production of hemp straw in France is estimated at 65,000 MT, which equates to almost 85% of European production, making France Europe's number one producer. This straw production breaks down into 17,500 MT of fibre and 32,500 MT of stalks (Ernst & Young study, 2005). Europe's main producers after France are Germany and the UK.
European production of flax and hemp fibres is in competition with the world's major exotic plant fibres such as cotton, jute, ramie, sisal, raffia, etc., and synthetic fibres such as glass or polyamide fibre.
The markets for flax and hemp fibres
The market for flax fibres depends on the nature of the fibres. These may be distinguished according to length: long fibres (approximately 60 mm) and short fibres (between 30 and 50 mm). Long fibres are used essentially in textile applications. Clothing, household linen and furnishing fabrics account for some 90% of the use of these fibres, with the remaining 10% earmarked for technical usage (sacks, tarpaulins, postbags). As far as short fibres are concerned, 20% are used for textiles (household linen), 60% are used in the paper industry and the rest find their way into the new applications for nonwovens. Depending on the country, the use to which hemp fibres are put will vary. So, for example, in Germany production is essentially intended for technical fibres (nonwovens, insulation wool), whereas France and Spain dedicate their production to the paper industry.
New applications for flax and hemp fibres in the composites industry
In addition to traditional applications, new applications are emerging, in particular in the automotive and building industries. New composite materials based on plant fibres and polymers are being increasingly used in the building industry in the United States and in car manufacturing in Europe. Plant fibres, such as flax or hemp, can be used as a reinforcement for PVC, PE or PP-type polymers in place of synthetic fibres (glass, Kevlar, carbon, etc.). This substitution offers many benefits:
Hot compression moulding technology generally requires a nonwoven mat, consisting either partially or entirely of plant fibres that may or may not be combined with synthetic fibres. During processing, at a temperature of approximately 180°C, the synthetic fibres melt and thus constitute a matrix in which the plant fibres are embedded. These nonwovens are used as interior linings for car doors, parcel shelves, boots or pillars. The majority of European car manufacturers have at least one model equipped with these kinds of linings in their range.
The processing of plant fibres by means of injection and extrusion is today on an upward growth trend, particularly in Europe. These technologies use plant fibres in combination with polypropylene, polyethylene and ABS. They can be used to manufacture objects with complex shapes. This type of material is marketed in the form of pellets that can be used in injection or extrusion processes. The main applications for injection moulding include structural parts for the car industry, for example. Extrusion is used to produce profiles, hollow components, etc.
The approaches that are in competition with the use of plant fibre/polymer composites are those using wood/polymer composites in which wood flour in ratios of up to 70% is introduced into the polymer matrices. These composites have made spectacular inroads on the US and Japanese markets in particular these last 10 years.
In the building sector, the use of plant fibre/polymer composites as construction materials is still very limited, yet it stands every chance of burgeoning on account of concerns relating to the toxicity of wood preservation treatments based on chromium and copper. Products developed include window profiles, fences, shutters, gates, decking (terrace floors, outdoor profiles, etc.), siding (shingles, swimming pool railings, etc.).
Other potential sectors are also being developed: public works (pipes), furnishings, materials handling (pallets), packaging, electrical and electronic goods, aerospace, boatbuilding, and consumer products.
Development prospects for plant fibre/polymer composites
The development of plant fibre/polymer composites is at an emerging stage since they currently represent a mere 0.1 to 0.5% market share, depending on the type of application. This market, estimated at 14,000 MT in France in 2005 by Alcimed, is set to grow rapidly on account of the increasing cost of oil and the crisis affecting the automotive sector. Indeed, some specialists believe that the widespread use of these materials could bring innovation into the sector and provide it with renewed momentum. In its prospective study carried out on behalf of ADEME in 2007, Alcimed forecasts that French production of plant fibre/polymer composites could reach 650,000 MT in 2015, rising to 1,150,000 MT in 2030. To achieve these objectives, the industry needs the support of R&D and help in its structuring. In the field of R&D, several programmes have been initiated by the public authorities and, in particular, by ADEME in order to relieve the technical sticking points that have been identified in relation to the use of these new materials. The main lines of research include the improvement of fibre properties via a better understanding of their constituents and their physical/chemical characteristics, and mastering their reproducibility and their adaptability to specific technical applications. Researchers are also focusing on the use of processing technologies, and in particular plant fibre extraction techniques, the processing of fibres in order to facilitate their adhesion to the polymer or biopolymer matrix (functionalization, sizing, etc.), the optimisation of current processes in order to adapt them to plant fibres (temperature and pressure resistance, stability, etc.) and understanding the evolution over time of the properties of fibres used in products (ageing, etc.). As far as the structuring requirements of the plant fibre/polymer composites industry are concerned, ADEME is providing global support to the plant fibres industry as a whole by bringing together the various players (scientists, technologists, plant fibre producers, processors and users) in producing general studies, and by organising technical or brainstorming sessions on this theme. Such studies include the market study of the new uses for plant fibres conducted by Ernst & Young in 2005, and a study carried out in 2007 by Alcimed to assess the current market for industrial bio-products and biofuels and forecast developments by 2015/2030.
At the scientific level, several notable advances have been made in the labs concerning structural parts for the automotive industry. However, these still remain to be validated on an industrial scale. In terms of the structuring of the industry, it may be noted that the hemp channel has moved ahead in the composites field. As far as flax is concerned, the organisation of this channel tends to be directed more towards "technical fibres" dedicated to high-performance materials.