Flax/Linen fiber is a natural, bast fibers which is obtained from the stem of the flax/linseed plant. It is Originated from Mediterranean region of Europe. Flax is produced in soviet union, Poland and France countries. France is the worlds major flax producer. Species and family of flax are Linum usitatissimum, linaceae respectively. Height of plant is 0.9 to 1.2 meter. Diameter of Stalks is 2.5 to 4 mm. Flax is one of the oldest fiber which grows in cool, damp environments.
Processing of flax fiber:
Harvesting:
Flax plants ready to be harvested when the quarter part of stem becomes yellow and before the fruit is fully matured. It can be done by two ways.
cutting the stalks very close to the roots
pulling up the entire plant by hand after this the plants has dried
Rippling/ Threshing/Winnowing:
It is nothing but the removal of seeds from plants by a machine.
Retting:
There are 4 types of retting processes. Any one process can be followed to separate the fibers from the stalks.
Biological retting:
Dew retting, water retting and enzyme retting comes under biological retting.
In the dew retting, the flax stalks spread on the field and expose them to sun and rain for several weeks until the stalks begin to separate from the fiber naturally. But this method reduces the quality and strength of the fiber.
In the water retting process, the bundles of stalks are immersed in water of at least 60 cm in depth until the fibers separate from the stalks. This process takes around 2 weeks. Then the bundles were taken out of the water and left to dry.
In the enzyme retting process, fibers can be separated from the stalks by using enzymes like pectinase and xylanase. It is the safest and fastest process of retting.
Mechanical retting:
In this process decorticator is used to separate the bast and core fibers.
Stalks will be feeded by feeding mouth, then they will enter to beaters to crush the stalks. Then the crushed stalks which contains both bast fiber and core fiber will be pushed into delivery plate and will be separated manually.
Chemical retting:
In this process, the stalks are boiled with acids and alkalies such as sodium hydroxide, sodium benzoate and hydrogen peroxide for several hours at a specific temperature and then washed with clean water. Compared to other retting methods the fiber which is obtained from this method is usually felt and rough.
Physical retting:
It requires low processing time. It involves 2 steps which starts with modifying the surface by chemical treatment. Then the stalks will be subjected to steam explosion. In this the bast fibers will be separated from the core fibers by blowing apart. But this method only produces short fibers.
Scutching:
After retting, the stalks are crushed between two metal rollers so that the woody portion of the stalks can be removed. Removal of woody substance, linseed, shive and tow from the flax stalks is known as scutching.
Heckling:
Then the short fibers can be removed by using heckling combs by combing.
Chemical composition of flax fiber:
Properties of flax fiber:
Physical properties:
Length: 2 to 5 cm
Tenacity: 5.5 to 6.5 gm/den.
Elongation at break: 2.7 to 3.5 %.
Specific gravity: 1.50
Diameter: 12-16 micrometers
Standard moisture regain: 10-12%.
Strength (MPa): 500-900
Density (g/cm3 ): 1.4-1.5
Specific Modulus: ~41
Specific Strength: ~480
Diameter [µm]: 10-80
E-modulus [GPa]: 50-70
Tensile strength [GPa]: 0.5-1.5
Elongation to fracture [%]: 2-3
Specific E-modulus [GPa per g/cm3 ] : 36-50
Specific tensile strength [GPa per g/cm3 ]: 0.4-1.1
Color: yellowish to grey
Resiliency: Very poor
Cross section: irregular polygonal shape
Feel: cool to touch because of higher conductivity
Effect of heat: It has an excellent resistance and a good conductor of heat
Effect of sunlight: not affected by sunlight
Luster: It is brighter than cotton and slightly silky
Abrasion resistance: moderate
Absorbency: It can absorb up to 20% of its own weight in moisture
Chemical properties:
Effect of acids: It is damaged by concentrated acids but not damaged by weak acids.
Effect of alkali: Resistant to alkaline solutions
Effect of organic solvents: Highly resistant to organic solvents
Effect of micro-organisms: It is attacked by fungi and bacteria but it is not attacked by moth, grubs and beetles.
Dyeability: Does not have good affinity to dyes. It can be dyed by using direct and vat dyes.
Effects of Bleaching Agents: It does not affected by Cool chlorine and hypo-chlorine bleaching agents.
Uses of flax fiber:
It is used for making
Bed linen, kitchen towels, handkerchiefs, table wear, upholstery, draperies, wall coverings.
High quality papers, luggage fabrics, sewing threads, filtration.
It is used in automotive industry.
It is also used for apparel.
Advantages:
It is biodegradable.
It is smooth, non-static, non-pilling and non-allergenic.
It is insect repellent.
It is breathable.
It has rich, elegant, luxurious look.
It gives UV protection.
It is very strong and absorbent.
It is very comfortable to wear and dries quicker than cotton.
It is washable and gains strength when wet.
It can withstand very high temperatures while washing and ironing.
It is free from lint.
It has good abrasion resistance.
It draws heat away from the body.
Disadvantages:
It wrinkles very easily unless applied with a special finish.
It has poor elasticity
It has poor drape
It has less durability
Without recovering its shape, it tends to stretch
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