Bast Fibers

Bast Fibers

 

fibers contained in the stalks of terrestrial seed plants; long prosenchyma cells lacking in live contents. The walls of bast fibers are markedly and uniformly thickened, often with pronounced stratification, simple pores, and a very narrow cell cavity. The average length of a bast fiber is 1-2 mm, but primary fibers originating from the procambium are generally longer (20-400 mm), while secondary ones (of cambial origin) are shorter. The walls of bast fibers in many plants are saturated with lignin; in some plants the membranes of the fibers consist almost solidly of cellulose and are elastic and very strong.

Industrial bast fibers obtained by primary treatment of bast plants are widely used in the textile industry to manufacture yarn. The following kinds of bast fibers are distinguished: thin, pliable, slightly lignified fibers (flax, ramie) and coarse, thick-walled, markedly lignified ones (hemp, kenaf, jute, abaca). Industrial bast fibers consist of bundles of elementary fibers glued together. Yarn from flax fibers is used to make cloth; that from sisal, hemp, and abaca fibers, to make rope, cord, twine, strands for steel cable, and so forth; that from jute and kenaf fibers, mostly to make sacks. Abutilon fibers are brittle and therefore have limited use in the textile industry. They are used to make sacks and cable in which they replace jute fibers.

Primary processing of bast crops involves biological (retting) and mechanical (breaking, scutching, separation of bast) processes and includes the obtaining of stock (from flax, hemp, and sometimes kenaf stems) or bast (from jute and kenaf stems), and of bast fibers from the stock or bast. The commonest method of preparing stock is dew retting or spreading: after threshing, the stems (straw) are spread on a meadow or field in even rows where they lie for 15-25 days. Owing to the action of mold fungi (Cladosporium herbarum and Alternaria tenuis), heat, moisture, and light, pectin and other substances in the stalks decompose and the bond of the bast fibers with the surrounding tissues is destroyed. With cold-water retting, the straw in sheaves, bales, and containers is submerged in a body of water (retting pond, artificial rettery) for 10-15 days. The bast fibers are separated from the tissues as a result of the activity chiefly of pectin-fermenting bacteria (Clostridium felsineum and C. pectinovorum). In flax and hemp mills, retting in water heated to 36°-37°C is used to make industrial stock. The stock is obtained in 70-80 hours or in 24-48 hours if accelerators (urea, ammonia water) are used. The process can be speeded up even more by steaming the straw in autoclaves under pressure of 2-3 atmospheres (for up to 75-90 minutes) and then soaking it in a weak solution of soda ash, acids, and a special emulsion (for up to 30 minutes). The stock is dried and processed in breakers and scutchers where the fiber is freed from woody tissue (boon) and epithelial and parenchyma tissues.

Bast is separated from the stalks in a bast-separating machine, then subjected to biological retting and treated in a scutching and washing machine. The bast fibers are dried, softened, and graded. The technology by which bast is first obtained from stalks is also promising for flax.

REFERENCES

Derbenev, S. I., I. Ia. Lunev, and K. M. Mironov. Tekhnologiia promyshlennoi biologicheskoi mochki lubianogo syr’ia, 2nd ed. Moscow, 1968.
Egorov, M. E., and Ia. A. Lebedev. Pervichnaia obrabotka I’na-dolguntsa v kolkhozakh i sovkhozakh. Moscow, 1968.
Markov, V. V. Pervichnaia obrabotka lubianykh kul’tur, 2nd ed. Moscow, 1969.
References in periodicals archive ?
Upon completion of internode elongation, a cambium (thin cylinder of meristematic tissue running the length of the stem), located internally to the primary fibers, produces (a) secondary bast fibers towards the outside of the stem (but inside the primary bast fibers) and (b) xylem (woody "hurds" tissue) towards the center of the stem.
offers cost-effective and environmentally sustainable natural fiber in the form of flax, hemp and other bast fibers for use in textile, industrial, energy, medical and composite material applications.
The topics include the physiology and botany of industrial hemp, legislative controls on the cultivation of hemp, integrated quality management for bast fibers in technical applications, hemp in papermaking, hemp seeds for nutrition, chemical and morphological differences in hemp varieties, and the role of hemp in sustainable development.
Kenaf yields two raw materials and the outer bast fibers have many textile applications, both woven and nonwoven," says Galvin.
The basic materials of wood shavings, kenaf bast fibers (hereafter "kenaf"), and bicomponent fibers are shown in Figure 1.
However, the strength of the milkweed stem fibers is similar or higher than that of other common bast fibers such as jute and the fibers obtained from various agricultural byproducts (14-20), (30).
In 1957 tissue-like paper made from hemp bast fibers was found in a Chinese tomb dated c.
The book opens with a discussion of microbial processes in fiber degradation, then goes on to look at major fiber types, including bast fibers, alginates, cellulose, and specialty biodegradable fibers such as lyocell.
The bast fibers were longer than many hardwood fibers, having an average length of 1.
Leading contenders for wood and glass replacement are bast fibers from flax, hemp, and kenaf.
Progress in biotechnological modification and functionalisation of bast fibers for advanced applications Vincent A.
MG-cp-2 in degumming of ramie (Boehmeria nivea) and sunn hemp (Crotalaria juncea) bast fibers.