Bast/stem fibres

Bast or stem fibres These fibres come from the inner bark of the stem of plants. Common examples are jute, flax, hemp, kenaf and ramie. 

Cellulosic fibres from vegetable sources other than cotton and wood are used in a variety of textile and industrial products. These fibres are mostly obtained either from the leaves of tropical plants or from the stems of reed-like plants. Leaf fibres are generally stiff ( hard fibres ) and are used mostly for cordage. Stem fibres (also known as bast fibres) are usually finer ( soft fibres ) and find use in textile applications. The cellulose content of these materials is usually in the range 70—90% (on dry weight). The more important commercial products and their principal usage are shown below. 

Vegetable fibre, those derived from the seed, stem, wood, bark (bast fibres), leaf, or fruit of plants. They are composed chiefly of cellulose (up to 90%), the remainder being primarily lignin, hemicellulose, and pectins. 

Cellulose fibres originate from the seed of the plant (cotton), its stem (bast fibres) or its leaves (sisal, alfa), having, as a consequence, different percentages of cellulose, lignin and hemicellulose. Basically, any plant may be used as a source of cellulose fibres, and it is a matter of historical development, availability and abundance that cotton, hemp and linen (flax) are today the most used cellulosic fibres. 

Bast fibres are obtained from the stems of the corresponding plants hemp is a variety of Cannabis saliva L (diflfering from marijuana by having a considerably low content of A-9-tetrahydrocannabinol, the narcotic substance), and flax is obtained from the plant Linium usitatissimum. The fibres contain 70-75% cellulose, with about 4% lignin, 17% hemicellulose and 6% pectin in hemp and... 

Natural fibres can be subdivided into plant, animal, and mineral fibres. All plant fibres (cotton, jute, flax, hemp, etc.) are made of cellulose animal fibres are made of protein (wool, silk, hair). Based upon their origin, plant fibres are subdivided into bast and hard fibres. Bast fibres are derived fix)m the stems or stalks of plants hemp, jute, ramie, and flax, for example, belong to this category. Hard fibres, on the other hand, are derived from leaves, leaf sheaths, or fruit sisal and coconut belong to this category ... 

From the bark of the hemp stems, bast is obtained. The bast fibres are separated mechanically from the woody parts modern separation methods employ enzymes or steam pressure, surfactant or ultrasound processes. The best hemp fibres are obtained from the male plants being very durable. They are used for the manufacture of ropes, cords, nets, strings, yarn, carpets, textiles and sailcloth. The wood is used for the manufacture of insulating material, but it is also well suited for the production of paper, cardboard and cartons, since its lignin content amounts to only 10% (compared to 20-25% from trees). 

Flax is one of the oldest fibre crops in the world. It is extracted from the bast or skin of the stem of the flax plant. The fibre is soft, lustrous and flexible and, when bundled, has the appearance of blonde hair. It is stronger than cotton fibre but less elastic. The best grades are used for linen fabrics such as damasks, lace and sheeting. 

Natural fibres are classified into three main groups, namely, bast (or stem), leaf and seed (or fruit). Bast fibres such as jute, hemp, kenaf and flax are fibrous bundles found in the inner bark of the plant stem. The fibre bundles consist of filaments of fibre cells made up of mainly cellulose and hemicelluloses. The cementing material between the fibre bundles is lignin while the filaments are held together by pectins. These fibres are separated from the woody matter through a process of natural... 

Nature in its abundance offers us a lot of material that can be called fibrous fibres are found in plant leaves, fraits, seed covers and stalk. Fibres from these plants can be considered to be totally renewable and biodegradable. Bast fibres are soft, woody fibres obtained from stems of dicotyledonous plants (flowering plants with net-veined leaves). Such fibres, usually characterized by fineness and flexibility, are also known as soft fibres, distinguishing them from the coarser, less flexible fibres of the leaf, or hard , fibre group. This chapter will discuss bast fibres from flax, hemp, jute, ramie, kenaf and abaca. 

Before straw is processed and fibres extracted, it has to be retted. In Asia, Africa and Latin America kenaf is still retted in ponds. However, this process is labour intensive and leads to serious contamination of waterways [47,49], therefore, like many other bast fibre yielding crops, kenaf can be dew-retted. The second stage of processing involves a series of decortication machines that break the stem and separate core and bast fibres [50]. 

The fibres that were desaibed above as being used for natural geotextiles, are usually extracted from four varieties of the woody-stemmed herbaceous dicotyledons (i.e. the bast fibres flax, jute, hemp and kenaf), one of the monocotyledonous plants (i.e. sisal) and one of Palmaceae (palms) (i.e. coir) [13, 14]. 

Hard fibres (also termed leaf and structural fibres) are larger and stiffer than bast fibres, hence the name. They grow throughout the leaves or stem of monocotyledonous plants and like the bast fibres they give rigidity to the plant and also transport water and plant food from one part of the plant to another. 

Bast fibres are collected from the fibrovascular bundle region of plant stems, known as bast (or phloem), located between the epidermis or bark smface, and an inner woody... 

With dew or field retting, plant stems are cut or puUed up and left in the field for 4—5 weeks to allow dew and rainfall to affect the process under suitable climate conditions including air, humidity and ambient temperature. The process is monitored to avoid underretting or overretting to ensure that the bast fibres separate firom the inner core without much deterioration in quafity. The dew retting process is weather dependent and time-consuming, so it is usually replaced by other methods. 

The classification and properties of natural fibres for cement reinforcement have been reviewed in several publications [1-5]. Cook [1,2] has suggested four classes of fibres, based on their morphology stem (or bast), leaf, surface and wood. 

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