18-08-2012, 11:19 AM
CHINA GRASS
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INTRODUCTION
Ramie (pronounced Ray-me) is one of the oldest vegetable fibres and has been used for thousands of years. It was used in mummy cloths in Egypt during the period 5000 - 3000 BC . It has been grown in China for many centuries . Ramie (Boehmeria nivea), commonly known as China grass , white ramie, green ramie and rhea, is one of the group referred to as the bast fibre crops. The ramie plant is a hardy perennial belonging to the Urticaceae or Nettle family, which can be harvested up to 6 times a year. It produces a large number of unbranched stems from underground rhizomes and has a crop life from 6 to 20 years . Chemically ramie is classified as a cellulose fibre, just as cotton, linen, and rayon.
The main producer counties are reported to be China, Brazil, Philippines, India, South Korea and Thailand . Brazil began production in the late 1930s with production peaking in 1971 with about 30,000 t. Production in the Philippines began in the early 1950s, peaking in the mid 1960s with 5,500 t. Since then, production has declined steadily .
The main importing countries are long before cotton was introduced in the Far East, it was used for Chinese burial shrouds over 2,000 years ago. Ramie's popularity increased in the mid 1980s with a fashion emphasis on natural fibres.
NEED FOR A REGENERATED ECO – FRIENDLY FIBRE
The main drives of change and innovation in textiles are consumer demands for comfort and performance . In the development of fibres , yarn and fibric functional aspects such as anti bacterial , antistatic , UV protection and thermal or biodegradable functions are playing an increasingly important role .
PRODUCTION OF RAMIE FIBRE
Ramie fibre is extracted from the stem of Boehmeria nivea. The fibre is embedded in the cell of the bast (phloem), which lies between the outer bark and woody core. The spinnable fibre is obtained by decortications and degumming. The fibre is composed of a long single cell, which is fixed together in bundles by gums and pectins . Ramie is considered to be the longest, toughest and silkiest of all cellulosic fibres. It is used as a textile fibre and for various other applications. The stem of this bast fibre plant is made up of the pith and xylem, cambium, phloem (bast), cortex and epidermis. The bast fibres are obtained from the phloem, located in the inner bark, outside the cambium. It contains the commercially important bast fibres, seive tubes, parenchyma cells and sclereids. The fibres are arranged in long bundles, forming a continuous ring along the length of the stem. In the bundles, the fibres are joined together by the middle lamella, which is composed of pectin . These bast fibres provide both rigidity and flexibility to the plant stem .
YARN PROCESSING OF RAMIE FIBRE
Harvesting
Ramie is normally harvested two to three times per year but under good growing conditions can be harvested up to six times per year. The timing of the harvest of a particular stem is important as fibre yields are reduced if it is immature. As well, there are difficulties in removing the fibre if the stem is over mature.
Harvesting is done just before or soon after the onset of flowering, since there is a decline in plant growth at this stage and maximum fibre content is achieved. Stems are harvested by cutting just above the lateral roots or the stem can be bent, to enable the core to be broken and the cortex can be stripped from the plant in situ. Mechanical harvesters have been developed but are not used commercially. After harvesting, stems are decorticated while the plants are fresh as the bark gets harder to remove as the plant dries out. The bark ribbons are dried as quickly as possible to prevent attack by bacteria or fungi.
Ramie fibre
Ramie fibre is one of the premium vegetable fibres. The ultimate fibres are exceptionally long and are claimed to be the longest of vegetable origin, with one report claiming the fibres range up to 580 mm, averaging about 125 mm. Another report describes the ultimate fibre as ranging between 48 and 290 mm in length.
One US study reported the range of bark fibre length as 5 to 36 mm and the fibre width as 41.8 microns . Ramie fibre is very durable, is pure white in colour and has a silky lustre. It is reported to have a tensile strength eight times that of cotton and seven times greater than silk. However, other reports claim that the tensile strengths of cotton, flax, hemp and ramie are similar.
These discrepancies can be partly attributed to the effects of source of supply, method of processing, the test conditions, temperature and humidity, on the fibre strength.
Conditions Required for Growing
Ramie grows well in the areas having good rainfall and warm climate. The following type of soil and climate is best suited for ramie cultivation.
Soil - The soils best suited for ramie are sandy loam or loamy, very sandy. The clayey or gravel soil is not suitable. The plant is too much sensitive to soil moisture conditions. It grows well in land, which have adequate supply of moisture, well distributed throughout the growing season. Soil must be well-drained i.e. high land and should have no problem of water logging or flooding. Flat and slopy lands are good. Ramie plants give poor growth in the dry sandy soil and the poorly drained soils. The soils deficient in calcium and poor in Base Exchange capacity are also not suitable unless proper liming is done and sufficient organic manure is added. The pH of the soils for ramie should be around 5.5 to 5.6.