Write some useful information about plant fibres : source and uses flax
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Recently natural and made-man polymer fibres are used for preparation of functionalised textiles to achieve smart and intelligent properties. There are numerous application possibilities of these modified materials. Main pathways for functionalizaton of fibres are: inclusion of functional additives (inorganic particles, polymers, organic compounds); chemical grafting of additives on the surface of fibres and coating of fibres with layers of functional coatings. A new approach to produce new materials is by nanotechnology, which offers a wide variety of possibilities for development of materials with improved properties. Composites of cellulose fibres with nano-particles combine numerous advantageous properties of cellulose with functionality of inorganic particles, hence yielding new, intelligent materials. For preparing cellulose composite materials profound knowledge about fibres properties is needed. Besides, new fibre qualities are demanded to guaranty the modification efficiency. Therefore non-standard methods are involved to determine physical properties of fibres.
In addition to, manufacture, use and removal of traditional textile materials are now considered more critically because of increasing environmental consciousness and the demands of legislative authorities. Natural cellulose fibres have successfully proven their qualities when also taking into account an ecological view of fibre materials. Different cellulose fibres can be used for textile and technical applications, e.g. bast or stem fibres, which form fibrous bundles in the inner bark (phloem or bast) of stems of dicotyledenous plants, leaf fibres which run lengthwise through the leaves of monocotyledenous plants and fibres of seeds and fruits. Flax, hemp, jute, ramie, sisal and coir are mainly used for technical purposes. Recently, the interest for renewable resources for fibres particularly of plant origin is increasing. Therefore several non-traditional plants are being studied with the aim to isolate fibres from plant leaves or stems.
2. Plant fibres
Many useful fibres have been obtained from various parts of plants including leaves, stems (bast fibres), fruits and seeds. Geometrical dimensions of these fibres, especially the fibre length depends mainly on fibre location within the plant. Fibres from fruits and seeds are few centimetres long, whereas fibres from stems and leaves are much longer (longer than one meter) [Blackburn 2005].
All plant cells have a primary wall. During cell growth and after it has stopped, the cytoplasm in sclerenchyma cells dries while the cell wall becomes thickened by addition of a thick and rigid secondary cell wall which is formed inwards of the primary cell wall and constructed of cellulose fibrils. The secondary cell wall is formed by successive deposition of cellulose layers, which are divided in three sub-layers (S1, S2 and S3), of which the middle layer is the most important for fibres mechanical properties. It consists of helically arranged microfibrils. The diameter of microfibrils is between 10-30nm [John 2008]. An important parameter of the structure of the secondary wall is the angle that the cellulose microfibrils are making with the main fibre direction. Actually each of three fibres sub-layers has a different microfibrillar orientation [ Krässig 1992, John 2008, Cuissinat 2008] which is specific for the fibre type. Due to the formation of a thick secondary wall, the lumen becomes smaller.
The cell wall in a fibre is not a homogeneous layer. The walls of plant cells (the primary and the secondary cell wall) can be considered as a composite consisting of cellulose fibrils embedded within a matrix of lignin and hemicellulosic polysaccharides [Krässig 1992].
Flax is grown for its seeds, which can be ground into a meal or turned into linseed oil, a product used as a nutritional supplement and as an ingredient in many wood-finishing products. Flax is also grown as an ornamental plant in gardens. Moreover, flax fibers are used to make linen.
Flax, (Linum usitatissimum), plant of the family Linaceae, cultivated both for its fibre, from which linen yarn and fabric are made, and for its nutritious seeds, called flaxseed or linseed, from which linseed oil is obtained.