Soft bast

There are several different classifications in terms of plant fibers. While the classification of Nishino [59] includes seven groups as bast (soft) fibers (flax, hemp, jute), leaf (hard) fibers (sisal, abaca, pineapple, etc.), stem fibers (bamboo, banana stalk, corn stalk), fruit fibers (coconut), seed fibers (cotton, baobab, kapok), straw fibers (rice, wheat, corn), and others (seaweeds, palm), that of Faruk et al. [3] has six groups bast fibers (jute, flax, hemp), leaf fibers (abaca, sisal and pineapple), seed fibers (coir, cotton and kapok), core fibers (kenaf, hemp and jute), grass and reed fibers (wheat, corn and rice) and all other types (wood and roots). 

Vegetable fibers are classified according to their source ia plants as follows (/) the bast or stem fibers, which form the fibrous bundles ia the inner bark (phloem or bast) of the plant stems, are often referred to as soft fibers for textile use (2) the leaf fibers, which mn lengthwise through the leaves of monocotyledonous plants, are also referred to as hard fibers and (J) the seed-hair fibers, the source of cotton (qv), are the most important vegetable fiber. There are over 250,000 species of higher plants however, only a very limited number of species have been exploited for commercial uses (less than 0.1%). The commercially important fibers are given ia Table 1 (1,2). 

China jute Abutilon Bast or soft fibers Abutilon theophrasti China... 

China jute Bast nr soft fibers A bunion Abntifon China... 

Bast is the inner bark of a plant, composed of the phloem and other fibrous cells. Hard fiber, which comes from leaves, is used mostly for cordage (rope, twine, cord) and the rough fabric used for making sacks and other containers. Soft fiber, which comes from plant stems, is used to make thread and finer fabrics like linen, cotton, and woven hemp. 

Conducting Parenchyma.— This type of parenchyma functions in the rapid translocation of food materials to distant regions in. the plant. It includes the wood parenchyma cells of the xylem which convey a portion of the crude sap (water with mineral salts in solution) and the phloem parenchyma (soft bast) which transports the elaborated sap (carbohydrate and proteid material in solution). Conducting parenchyma cells differ from those of ordinary paren-Digitized by Microsoft ... 

Secondary Phloem Soft Bast—phloem cells and sieve tubes. Cambium—active layer giving rise to secondary phloem on outer and secondary xylem or inner face, and adding to depth of med. rays. Secondary xylem—wood fibers, pitted vessels, tracheids. 

Jute and kenaf fibers develop in the phloem, or bast, region of the stem of the plants, and they appear as wedge-shaped bundles of cells intermingled with parenchyma cells and other soft tissues (Figure 7.1) in the transverse sections of the stem. In the growing part of the stem, a circumferential layer of primary fibers develops from the protophloem, but, as vertical growth ceases in the lower parts, secondary phloem fibers develop as a result of cambial activity. In mature plants, which reach a height of 2.5-3.5 m and a basal diameter of about 25 mm, the secondary fiber accounts for about 90% of the total fiber bundles. 

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 fibers are classified based on their origins, whether they are plant, animal or mineral fibers. All plant fibers are composed of cellulose while animal fibers consist of proteins (hair, silk, and wool). Plant fibers include bast (or stem or soft scleren-chyma) fibers, leaf or hard fibers, seed, fruit, wood, cereal straw, and other grass fibers [1]. Over the last few years, a number of researchers have been involved in investigating the exploitation of natural fibers as load bearing constituents in composite materials. The use of such materials in composites has increased due to their relative cheapness, their ability to be recycled, and because they can compete well in terms of strength per weight of material [2]. Provided below is the classification of natural fibers based on origin ... 

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. 

The fibres used for natural geotextile products are plant or vegetable fibres, although some research and development studies have considered the use of very low grade sheep s wool and wool waste. Figure 11.1 shows a classification of well known natural fibres. However, the only ones that meet with the technical requirements, cost effectively, are the bast fibres jute, hemp, kenaf and flax (also called soft fibres because they are from the softer region of the plants), and the hard (or leaf) and fruit fibres sisal and coir. Others of the remaining fibres, e.g. wood fibres, are sometimes used as fillers within the textile structure. 

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. 

Bast fibers contain a bit lower amount of cellulose (about 70%) than cotton ones. Moreover, they contain such components as lignin (10%), wax and trace amonnts of antibiotics, some of which increase biostability of the fiber. The presence of lignins induces coarsening (lignifications) of plant cells that promotes the loss of softness, flexibility, elasticity, and increased friability of fibers. 

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