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Mercerizing:

Mercerization is one of the most important finishing processes of cotton with caustic alkaline ( NaoH) solution in order to improve the lustre, hand and other properties. It imparts gloss to the fiber, increases its hygroscopicity, strength and improves its dye affinity. It improves the reactions with a variety of chemicals and elongation of the fibres and also improves the stability of form. Mercerizing process consists in treatment of cellulosic materials with concentrated solutions of caustic soda at a temperature of 15 to 18C.Purpose of mercerizing:

1.To improve the lusture.2.To improve the strength.3. To improve the dye uptake and moisture regain.

Effect of Mercerization:Improve Luster.Increase ability to absorb dye.Improve reaction with a verity of chemicals.Improve stability of form.Improve strength/elongation.Improve smoothness.The molecular cross-sectional reshaped.Recipe and parametersCaustic Soda- 35% strengthWetting agent: 0.5 to 1%Temperature: 18 degree centigradeDwell time : 55 secondPrinciples:Pad-- squeeze stretch hot or cold wash---dryMachine Working: Chain type and chain less type.In both case padding mangle is for padFor stretch either stenter and roller to be used. For chainless curved roller to be used for width tension.

Types of MercerizationMercerization are Two Types:

Tension Mercerization

The purpose of mercerization is to increase luster of Cotton fibers

The fiber untwists and swells, lumen becomes rounder in cross-section and it gains luster. Dye affinity and chemical reactivity increase. Fabric becomes stronger and smoother.

2) Slack Mercerization

Not as lustrous as tension method

Elongation and recovery properties improve and thus have been used to produce comfort stretch garments and fabric bandages, which need to conform to body shapes.

Larger dyeing affinityLarger dimensional stability of the articlesIncreasing of the lustreIncreasing of the tensile strengthBetter covering of dead and/or mossy cottonImproving to the touchTHE ADVANTAGES OF Mercerization: :Effects of the chain mercerization of cotton fabric

Note: Fabric Mercerization is Cheaper than double Mercerization which provides a softer handMercerization

Native cellulose (Cellulose I) forms alkali cellulose I with concentrated sodium hydroxide. On washing and neutralization cellulose II is formed.As a result of the penetration of the alkali into the lattice, internal hydrogen bonds arebroken and in Cellulose II the number of available hydroxyl groups (-OH) is increased by 25%. The process is commercially known as mercerisation. The treatment with alkali and subsequent washing may be performed so that the fabric or yarn may either freely contract or they may be held under tension. In both cases the mercerised cotton has an increased affinity for both reactive and direct cotton dyes, water and an increased strength. Cotton yarn or fabric mercerised without tension contracts, but if held under tension it retains its original dimensions and the lustre is increased.

THEORY:What is the mercerizing processThe mercerizing involves these three subsequent steps,

Impregnation of the material in in relaxed state,cold caustic solution of required strength and wettability..

Stretching while the material is still impregnated in the caustic solution.

Washing off the caustic soda from the material while keeping the material still in the stretch state.(1) Twaddle (Concentration of NaOH):If the concentration of NaOH is increased above 56oTw improvement inluster will be attained but if it is decrease below 48o Tw. The quality of luster willbegin to be adversely affected.

(2) Temperature:High degree of luster is attained at temperature 18-20oC. As thetemperature is increased the quality of luster is adversely affected but onlowering the temperature no improvement in the luster is obtained.

(3) Tension:For acquiring better luster the material must be stretch to its originaldimension (both in warp and weft direction during mercerization). If the materialis allowed to shrink duringmercerizingthen quality of luster will be impaired onthe other hand if the material is stretched more no improvement in luster isachieved.

(4) Time:The optimum time for mercerizing is 30-60 seconds by increasing theduration of time no applicable improvement in the quality of mercerization can beachieved but if the time limit is less than 30 seconds in the quality ofmercerization will be improved.Different mercerizing machinery/technology:Automatic hank yarn mercerizing m/c.Chainlesss mercerizing Machine.Clip or chain type mercerizing m/c.Open width fabric mercerizing m/c with caustic recovery unit.

Factors of Mercerizing:

In mercerizing followings are important:

Concentration of NaoHTemperatureTensionTimeluster of yarn after mercerization:

Before and after shade with same parameters

Image of Mercerizing M/C:

CHAINLESS MERCERISING RANGEChainless Mercerizing

Chainless mercerizing is practiced on a range where the cloth is maintained in contact with rotating drums virtually throughout the entire process. The tension on the fabric depends on the friction between the cloth and the surface of the drum. This results in good control of length but limited control of width. Bowed rollers are sometimes used to stretch the width but they are much less effective when compared with the clips of the chain Mercerizer. Chainless Mercerizing is used on fabrics that cannot be handled on a clip frame such as knits. Specialized equipment has been developed for Mercerizing tubular knit goods. CHAINLESS MERCERISING RANGE

CHAIN MERCERISING RANGE