Introduction:
Ramie is a natural vegetable, bast fiber which is obtained from the inner barks(phloem) of the stalks of ramie plant. It belongs to the Boehmeria species and Urticaceae (nettle) family. It is originated in China and cultivated in Japan, India, Malaya, Queensland, Mauritius, the Cameroons, the West, Mexico, Indies, Brazil, southern states of North America and South Europe. The life of crop is 6-20 years and can be harvested up to 6 times a year. It requires the temperature between 250 ͦ C-310 ͦ C and rainfall of 1500-2500 mm. It is also known as china grass, white ramie, green ramie and rhea.
Processing of ramie fiber:
Harvesting:
Harvesting should be done when the seed to form and flowers begin to fall. It is done manually or with mechanical harvesters. The stalks should be dried to prevent a bacterial attack if the ribbons are not to be stripped immediately after harvesting.
Decortication:
Decortication should be done immediately after the harvesting. If the decortication has not completed on the day of the harvest, they should keep moist by sprinkling water until decortication is done. If the stalks dried, decortication cannot be done properly. So the schedule for harvesting is planned according to the capacity of decortication machine. Removal of outer bark, central woody core, gums and waxes from the stems of ramie by hand or decorticating machine is called decortication. Stalks will be fed by feeding mouth, then they will enter to beaters to crush the stalks. Then the crushed stalks will be pushed into the delivery plate and will be separated manually. The quality of fiber depends on the condition of the plants and efficiency of the operator.
Washing:
It should be washed after the extraction of fiber.
Drying and Degumming:
After washing, it should be dried or degummed to prevent the attack of mildew.
Chemical composition of ramie fiber:
Properties of ramie fiber:
ultimate fiber cell length: 20 - 25 mm
ultimate fiber cell breadth is 15 – 80 µm
L/B ratio: 3500:1
cell wall thickness: 9 – 16 µm
gravimetric fineness: 0.40 – 0.80 tex
fiber filament tenacity: 40 – 65 g tex-1
fineness: 0.80 tex
extension at break: 3-4%
torsional rigidity: 1-2 (10-9)N/m2
flexural rigidity: 0.80-1.20 (10-9)N/m2
Length: 40-200mm
Diameter: 25-30µm or 0.034mm
Density: 1.50-1.55gm/cc
Tensile strength: 400-1600MPa
Fracture load: 0.467N
Fracture strain: 0.025%
Moisture content: 8.0%
Moisture regain: 12%
Thermal decomposition: 275 ͦc
Degree of crystallinity: 70%
Modulus of elasticity: 65+/-18 Gpa
It is highly crystalline fiber.
It is 6 times stronger than cotton.
It is identified by its coarseness, striated surfaces, thick walls and lacks twist.
It is resistant to sunlight.
It is resistant to mild alkalis.
It is resistant to bacteria. Mildew, rotting and insect attack.
Hydrolysis of cellulose and loss in strength takes place when treated with strong alkali and strong acids.
Degumming of fiber offers more attractiveness.
It can be blended with cotton, flax, wool, polyester, silk and acrylic.
Advantages and disadvantages of ramie fiber:
Advantages:
Wrinkles easily.
Strong and durable.
Good wetting strength.
It is extremely absorbent.
It does not shrink.
It can be bleached.
Resistant to stains.
During laundering, it can withstand high water temperature.
It is not dyed well due to high molecular crystallinity.
Lustrous appearance.
It has the ability to hold shape.
Disadvantages:
It has less elasticity.
Lacks resiliency.
It has less abrasion resistance.
It is poor in wrinkle recovery.
High cost.
Brittle and stiff.
Degumming is essential.
Less elongation potential.
Uses of ramie fiber:
It is used to make
Filter cloths, packing materials, industrial sewing thread, upholstery, canvas
Clothing
Napkins, handkerchiefs, table cloths
To gain certain properties, it is blended with other fibers. It offers dye affinity and luster when blended with high-quality cotton. When blended with rayon, it offers low wet strength. It minimizes shrinkage and adds lightness when mixed with wool.