DEVELOPMENTS IN MERCERIZATION

BY: RACHIT SETH

CONTENTS

WHAT IS MERCERIZATION ? TYPES OF MERCERIZATION PROCESS OF MERCERIZATION EFFECTS OF MERCERIZATION CHANGES DURING MERCERIZATION PROCESS COLD MERCERIZATION HOT MERCERIZATION COMPARISON OF MECERIZATION PROCESSES MERCERIZATION OF WOOL HOW THE MERCERIZATION PROCESS DEPENDS UPON

THE STRUCTURE OF THE YARN ? REFERENCES

WHAT IS MERCERIZATION ?

Mercerization is one of the most common wet processing of cellulosic materials to improve their physical and chemical properties.

Mercerization is defined as the treatment of cotton textiles with a concentrated solution of alkali.

Mercerization gives cotton woven cloth a silky lustre, and is the foundation of many improved and beautiful finishes.

Types of Mercerisation

Hot Mercerization

Cold Mercerization

PROCESS OF MERCERIZATION

A. Impregnation of the material in

relaxed state, cold caustic solution of required strength and wet ability.

B. Stretching while the material is still

impregnated in the caustic solution.

C. Washing off the caustic soda from the material while

keeping the material still in the

stretch state.

EFFECTS OF MERCERIZATIONIMPROVES: LUSTRE DYEABLIBILTY TENSILE STRENGTH MOISTURE ABSORBANCY ELASTICITY DIMENSIONAL STABILITY

CHANGES DURING MERCERIZATION PROCESS

PHYSICAL CHANGES1. Improvement in strength2. Improvement in luster3. Change in cross section from bean shape

to almost circular CHEMICAL CHANGES1. Formation of cellulose-II.2. Improvement in moisture regain.3. Improvement in dye uptake.

COLD MERCERIZATION

RECIPE

CONCENTRATION 31 to 35%

TIME 55 SECONDS

TEMPRATURE 15 to 180 C

TENSION OPTIONAL

MICROSCOPIC VIEW OF MERCERIZED COTTON

LATTICE STRUCTURE OF CELLULOSE I AND CELLULOSE II

DISADVANTAGES OF COLD MERCERIZATION

Penetration of grey cotton becomes more difficult.( high viscosity)

Swelling only in surface ( heavy fabrics) Poor mercerization at the core and lack

of uniformity.

HOT MERCERIZATION

RECIPE

Na OH 26-30%

Wetting agent 1%

Temp 60o C

Time 20 – 30 sec

ADVANTAGES OF HOT-MERCERIZATION

Rapid alkali penetration Improved core mercerization More uniform treatment Dwell time can be reduced from 50 sec

to 20-30 sec.

DISADVANTAGES OF HOT MERCERISATION

Less lustre ( due to lower swelling) Higher energy consumption Costlier

COMPARISON OF MERCERIZATION PROCESSES

PROPERTY CONVENTIONAL MERCERIZATION

HOT MERCERIZATION

Swelling speed Low Fast

Evenness Uneven Good

Luster Good Good

Dye uptake Good Not quite high

Dimensional stability Good Good

MERCERISED MERINO: the fine feeling of luxury apparel• The Mercerised Merino process uses special technology and

chemistry to reduce the thickness of the wool scales to make the fibre surface smoother.

• By oxidising the fibre the scale structure is loosened, making the fibre feel soft like cashmere; then the fibre is placed in an alkaline bath which dissolves the scale structure and makes the fibre appear brighter and more lustrous.

• A silicone polymer is also applied, increasing the fibre’s natural softness.

• By blending Mercerised Merino with cashmere, the actual burst strength is also improved by 15 to 20 per cent.

How is that done?

How mercerization process depends upon structure of yarn

The extent of change in the physical properties of the mercerized yarn depends on its structure.

To observe this hot mercerisation of open end spun yarn and ring spun yarns was done.

Open-end spun yarns are known to have good uniformity, less hairiness, and better strength, but their mean breaking strength is lower than the corresponding ring spun yarns. This has been attributed to the different structure of the open-end spun yarn.

Comparison between ring spun and open end spun yarn

RESULTS OF THIS EXPERIMENT

CRYSTALLANITY:- All caustic mercerization treatments caused a decrease in the crystallanity of cellulose. The crystallinity of the mercerized ring spun yarn is higher than the mercerized open-end spun yarn, at all conditions.

PENETRATION:- The open-end spun yarn has a relatively high packing density around the yarn axis, while the ring spun yarn has an intermediate packing density distribution , thus, the primary penetration of caustic soda into the open-end spun yarn is easier than that ring spun yarn.

MOISTURE REGAIN :- of slack mercerised open end spun yarn is more than the slack mercerised ring spun yarn.

DYE UPTAKE :- The dye uptake of slack mercerized yarns was higher than that of yarns mercerized under tension. Mercerized open-end yarns have gained higher increase in their dye uptake compared to the ring spun.

TENSILE STRENGTH :- improvement in tensile strength of mercerized open-end spun yarns was greater than the mercerized ring spun yarns.

SHRINKAGE :- Shrinkage in the ring spun yarns was higher than that of the open-end spun yarns. This may be due to the difference in fibre packing between both yarns.

CONCLUSIONS

Mercerization is more beneficial for open-end spun yarns than ring spun yarns.

REFERENCES

http://textilelearner.blogspot.com/2013/02/mercerization-of-knitwear-mercerization.html#ixzz2Qw3QIzcH

http://www.vdivde-it.de/innonet/projekte/textilien

http://textilefashionstudy.com/mercerizing-definition-mechanism-and-effects-of-mercerizing/

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