Flax

Submitted by-Lili

M.Sc (C.T) 3rd sem.

Textile classification-

The flax fiber is classified, as a natural, cellulose, bast, multi-cellular fiber. it is considered to be a heavy fiber, for this reason that most linen textile materials are of light construction. Thick linen textile materials would be uncomfortably heavy to wear.

Fiber morphology-

The macro-structure of flax-The flax fiber is a thick, regular fiber with a

subdued luster.

It ranges in length from about 10cm to 100 cm, averaging about 50cm in length.

As the flax fiber is a strand of cells, it thickness depends upon the number of these cells, about 3-6 cells constitute a fiber cross section.

The flax cells are about 25mm long and 10µm to 20µm thick. This would be give an average fiber thickness ranging from about 40µm to 80µm.

Its fiber length to breadth ratio is 15000:1 for the longest and the best flax and 1500:1 for Short flax fibers .

The color of flax varies from light blond to grey blond, the particular shade resulting from the agricultural and climatic conditions under which it was grown and the quality of retting.

The subdued luster of flax is due to its long regular fiber surface, which is coated with a film wax. This enables a significant amount of the incident light to be reflected, resulting in the subdued luster.

There may be up to 80 nodes in a single flax fiber cell. The length of the node indicates the width or thickness of the fiber cell.

Where ever a node occurs, it indicates a change in the spiral direction of the fibrils which constitute the cell walls.

Such spiraling imparts strength to the cell and, hence, to the flax fiber

Microscopic appearance of flax-

The cross markings, known as nodes, on flax fibers give them their characteristic microscopic appearance.

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The micro-structure of flax-

The flax fiber cell is covered with a wax film.

The cell walls of flax are constructed of spiraling fibrils composed of cellulose polymers.

On the whole, the flax cell is more sturdily constructed then the cotton cell, as indicated by the former’s thicker cell walls.

This explains, in part, the greater tenacity of flax compared with cotton.

The polymer system-

The flax polymer and its polymer system-it has a degree of polymerization of about 18000.

This means the flax polymer is about 18000nm long, and about 0.8nm thick.

The polymer system of flax is more crystalline , because of its longer polymers, spirals about each other at approximately 6° to the fiber axis, thereby contributing towards the tenacity and durability of fiber.

The greater crystallinity of flax fibers is demonstrate by the fact that they are stronger, crisper and stiffer to handle, and textile materials wrinkle more readily than those of cotton fibers.

Physical properties-

Tenacity-Flax is a very strong fiber because it’s very crystalline

polymer system permits its extremely long polymers to form more hydrogen bonds than cotton polymers.

Elastic-plastic nature-The very inelastic nature is due to very crystalline

polymer system.

It tends to lock its polymers into position with the aid of the countless hydrogen bonds which form between the polymers.

Flax will resist being flexed or bent,. When these are bent or flexed, their polymers are liable to break leading to fractures in the polymer system.

Hygroscopic nature-Flax fiber is very absorbent,

Owing to the countless polar –OH groups in its polymers, these attract water molecules, which are also polar.

Aqueous swelling of the flax fiber is due to a separation or forcing apart of polymers by the water molecules in the amorphous regions only.

The polarity of the water molecules, attracted to the hydroxyl groups on the polymers, dissipates any static charge which might develop.

Thermal properties-

Flax has the best heat resistance and conductivity of all the commonly used textile fibers. No satisfactory explanation can be offered for this.

Excessive application of heat energy causes the flax fiber to scouch, char and burn, This is an indication that flax is not thermoplastic,

which may be attributed to the extremely long fiber polymers and the countless hydrogen bonds they form.

Chemical properties-

Effect of acidsflax fibers are weakened and destroyed

by acids.

Acidic conditions hydrolyze the flax polymer at the glycoside oxygen atom, which links the two glucose units to form the cellobiose unit.

Mineral or inorganic acids, being stronger that organic acids, will hydrolyze the flax polymer more rapidly.

linen textile materials are not mercerized .

Normal laundering will result in alkaline hydrolysis of the waxes and gums bonding the cells forming the flax fiber together. This results in cell ends projecting above the surface of linen textile materials, and is referred to as cottonising of linen.

Several cottonising will cause a noticeable weakening of the linen textile material.

Effect of bleaches-

The most common bleaches used on flax textile materials are sodium hypochlorite and sodium per borate.

These two bleaches are examples of oxidizing bleaches, which is mostly used for flax textile materials. Oxidizing bleaches are so called because they liberate oxygen which does the actual bleaching.

Manufacture of Linen

1. Collection of plants- when the stems of the plant turns yellow at theseeds turn green to pale brown. The plants are pulled out by the roots. These are tied into bunches.

2. Drying and rippling- after pulling the

Flax, plant is tied in bundles and left to dry for few days. The leaves and seeds are removed from the stems by a process called Rippling. For this, the head of the stem is passed through coarse comb. After the removal of leaves and seeds, the stems are again tied up in bundles. Seeds are used for the production of Linseed oil.

3.Retting- this is an important process. The fleshy part of the stem is rotted by contact with water. Retting is a ferment process where the Pectin Ovurum(Pectin eater) bacteria eat the gum(pectin) which bind the fiber to the stem. There are 5 method of retting-

A. Dew retting-stems are spread out in fields and are exposed

to rain, sun and dew for several weeks, until, the stalk begins to separate from the fiber. It takes around 15-30 days. Because of long exposure to the sun and other natural conditions, causes to discoloration of the fiber.

B. Water retting- the bundle of the stems are kept in running orsegmented water for about 2weeks . Swift running of watercarries away the bacteria andthus slow down the fermentation. The

stem bundlesare covered with straw and stones are put

on thestraw to give extra weight. After 2 weeks

the stalks(upper portion of stem) separates out from

the fiberand the bundles are taken out of the water

and left todry.

C. Wooden vat retting- the stems are steeped in water at the controlled temperatur75°-90° in a Vat or in a container until the stems get soft. This is a fast process and the easiest method of retting and the quality of the fibers are good from this process.

D.Chemical retting- in this process the stems are treated with mild/dilute conc. Acid and alkalis then the fibers are easily removed from the stems.

E.Enzyme retting- enzyme retting is the safest and fastest process of retting, in this process the fibers can be taken out from the stems within few houres.

4.Breaking and scutching- when the stems are completely dry linen fiber are separated from these stems whenthe decomposed woody tissue is dry.It is crushable by passing through ironRollers. The breaking operation break the outer stalk. It reduces the stalkto small pieces of bark called slivers.

Scutching is done with the help of scutching machine which removes the broken slivers by means of rotating wooden peddles, thus releasing the flax fiber from the stem or it separates the fibers from woody stalk

5. Hackling or combing and spinning- during this process series of iron combs are used, ranging from coarse to fine. Fibers are pulled through the teeth of combs, beginning with the coarse one. The short fibers break off used for inferior quality Lenin called Tow linen. Then the spinning process is carried out-

Tow-lines Long staple or line Carding Carding Card Card Slivering Slivering Sliver Sliver Spinning Drawints RaningCoarse yarn(linen) Rove Spinning

fine yarn (linen)

6.weaving, finishing & dyeing- bleaching is given to the yarn and later on dyeing is done. The reason being the Linen yarn is in natural color i.e. grey or yellowish grey. Dyeing can not be done directly because it is not white in color. That is why bleaching is done before dyeing.

Thank you