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TEXFLAX: Processing and cultivation of short-fibre flax for high value textile end uses - LK0809

Description
(i) Aims:
a) to investigate alternative flax growing, harvesting and processing methods for the economic production of
high quality, short-fibre flax for high-value textile end uses;
b) to develop improved machinery for the cleaning, sub-dividing and stretch-breaking of short flax fibres;
c) to evaluate outcomes against current textile fibre quality and processing standards.

(ii) Background and Problems to be addressed
Recent UK flax cultivation has been heavily dependent upon subsidies for which the yield of both straw and seed were important criteria. EC subsidies are being phased out and without subsidy it is unlikely that short-fibre flax can be grown profitably using current farming practices which produce low quality, low value straw and fibre. The quality of flax fibre for the production of linen is not the issue to be addressed. Quality in this project is related to the usefulness of the fibre for processing on the short-fibre cotton spinning systems for the production of yarns that are used in the high-volume manufacture of fine fabrics. Such fabrics are currently dominated by 100% cotton and cotton/polyester blends. In these end-uses the stiffness of the flax fibres makes them relatively difficult to blend and spin into fine yarns when the proportion of flax in the yarn exceeds 20%. Coarser yarns, with higher proportions of flax, lead to fabrics which are themselves stiff, crease easily and tend to be prickly when worn against the skin.
Investigation of flax growing, retting and processing, led by the proposed project co-ordinator, has given strong indications that it should be possible to grow flax profitably in the UK without farming subsidy. The target market is that conventionally associated with cotton-based textiles. The criteria set by potential users in the textile industry are complex. In order to be used in conventional cotton products the 'quality' of the fibre needs to be improved and it would need to be reliably available in substantial quantities. Achievement of the appropriate quality is crucial; this requires a finer flax fibre with improved colour and an appropriate fibre length. The largest potential market for fine fibre is in blends with other textile fibres, especially polyesters, for ultimate conversion into apparel and industrial textiles. In this area fine flax fibres, of length between 15 and 40 mm and fibre diameter of less than 12 microns can be substituted successfully for cotton.
The world demand for cotton is increasing steadily and the acreage of cotton is tending to decrease as cotton growing requires prime agricultural land and a favourable climate. Typically, an average price for raw cotton is about £0.85/kg compared with a typical UK short flax fibre price of less than £0.20/kg. Good quality ‘cottonised’ flax currently sells at about £1.05/kg but the best qualities command prices much higher than this; when the elemental fibres are completely separated and the colour is near-white, prices as high as £2.50/kg are achievable. The world production of cotton fibre is some 19 million tonnes of which almost 6 million tonnes are exported by the producing countries. The EC is the world’s largest importer of cotton fibre and uses a little over 1 million tonnes annually; Italy alone imports almost 300,000 tonnes. If 10% of the EC consumption of cotton could be replaced with high-quality flax then about 100,000 hectares would need to be successfully devoted to fine-flax cultivation.
Although the concept of using short-fibre flax is attractive to the textile industry relatively little is used. Currently, high value long-fibre flax is almost exclusively used for linen production with short-fibre cottonised flax being produced as a by-product. There is limited use of cottonised flax in specialised high-value blends with cotton and other fibres. Low grade short-fibre flax is used in relatively low-value markets such as paper production, fibreboard and in some composites for the automotive industry.

Problems to be addressed
At present the demand for short flax fibre by the textile industry is small because it is not recognised as a valid raw material, this is due to past experience with by-products of the linen industry and the high prices demanded for good quality cottonised products. The total usage of short-fibre flax in apparel does not even approach 1% of the EC’s cotton fibre consumption.
There are problems with availability and continuity of supply of acceptable quality raw material. Attempts to modify flax fibre by secondary processing e.g. steam explosion or controlled retting have so far proved to be either inadequate or too expensive for large-scale production. Current UK production is not targeted at high-value short-fibre flax. Innovations from improved engineering of the processing equipment will allow some further progress but a more radical solution is necessary if the required fibre fineness is to be achieved. Despite the current situation, flax has attractive properties such as high strength, good moisture absorbency, high lustre and bio-degradability which makes short fibre flax desirable for the textile industry.
In order for flax to process successfully on cotton systems it needs to behave similarly to cotton. This requires a fibre length of between 15 and 40 mm (optimally 28-32 mm) and for spinning 100% flax yarns into fine yarns the fibres need to be finer than those currently produced (which are generally bundles of the elementary fibres). A fibre diameter of circa 5 microns with tensile, bending and friction properties similar to those of cotton would be ideal. Flax has sufficiently similar tensile properties but the bending rigidity is much higher than cotton of similar cross-section area because of the difference in cross-section shape; cotton fibres are flat, ribbon-like structures whereas elemental flax fibres are roughly circular. The surface friction of flax is higher than cotton, this has been associated with the higher lignin content of flax.
There has been no systematic search amongst the flax accessions to identify those whose elemental fibres have properties which approach those required for cotton substitution. One of the tasks will therefore examine the potential for growing flax accessions which could produce significantly finer elemental fibres. The potential for harvesting and retting flax early in the growth cycle will be explored to determine possible options for producing whiter and more easily subdivided fibre bundles. The mechanical processing of fibre will be investigated with the aim of improving straw decortication, cleaning, fibre separation and shortening processes and so improve fibre quality and process productivity. Flax spinning on cotton equipment will be investigated and the bleaching and dyeing of fine flax will be investigated to examine its compatibility with cotton in similar processes.
Objective
Technical and Scientific Objectives
(i)The main objectives are:
·To investigate the variation in the textile characteristics of the elementary fibres produced from an existing core collection (CGN’s genebank) of flax accessions.
·To determine the diversity of short-fibre properties from chosen accessions and at different stages of growth.
·To investigate the effects of premature artificial senescence, compared to later desiccation or pulling, on fibre characteristics, retting and ease of decortication.
·To identify the characteristics of flax fibres that may be used in the future choice of flax cultivars.
·To develop new processing machinery for improved fibre separation, cleaning and shortening.
·To establish best-practice recommendations for the bulk production of fine-fibre crops.
·To investigate the relationship between lignin content and the colour of flax fibres and the implications for bleaching and dyeing processes.

(ii)Chances of Success
There is a sound base of knowledge and experience within the partners based upon industrial practice and earlier investigations performed both by themselves and others. As a result there are clear indicators of the tasks that need to be undertaken. The principles for new methods of fibre cleaning, separation and shortening have been established. The target fibre specification for a cotton substitute flax fibre is known. Samples of flax straw for a wide range of fibre flax accessions grown under identical conditions are available for fibre characterisation.
The work plan focuses upon the most important factors that need to be addressed. This will ensure success in the delivery of new knowledge, understanding of the problem and the generation of practical, exploitable, outcomes.
(iii)Risks
The main risks relate to the limited quantitative information on the ultimate fibre characteristics in different flax accessions. Reports of 'better quality fibre' rarely give any objective quality criteria in terms of the elemental fibre fineness, length or tenacity and are invariably related to linen fibre production. Flax fibres are reported to have a wide range of diameters, quoted values range between 5-30 microns. Information from the Vavilov Institute of Plant Cultivation is of much greater value as it clearly indicates that fibre linear density, flexibility and tenacity vary considerably from accession to accession but unfortunately the test methods are not defined.
Those tasks which relate to improved fibre fineness are, therefore, dependent upon the initial selection of finer-fibre varieties being achieved in the early stages of the investigation. Despite the difficulties, the chances of success have improved considerably following the establishment of collaboration agreements between the DMU and both CGN (Netherlands) and the Vavilov Institute (Russia).
Time-Scale and Cost
From: 2002

To: 2005

Cost: £370,874
Contractor / Funded Organisations
Syngenta Crop Protection UK Ltd, G & R Burgess, C Strout, Cebeco (Seed Innovations) Ltd, BSN Medical Ltd, Garnett Wire Ltd, University - De Montfort, Filartex S.p.A, Biofibre Ltd
Keywords
Agri-Industrial              
Arable Farming              
Crops              
Farming              
Fields of Study
Non-Food Crops