Presentation on Mercerizing
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Mercerizing is a finishing process for cotton that improves properties like luster and strength. It involves treating cotton with a strong alkaline solution, usually sodium hydroxide. John Mercer discovered the process in 1844. The sodium hydroxide penetrates the cotton fibers and reacts with hydroxyl groups, swelling the fibers longitudinally and altering the cellulose structure. This gives mercerized cotton increased luster, strength, dye uptake, and other improved qualities. The degree of mercerization depends on processing conditions like tension, concentration and time in the alkaline solution.
Presentation on Mercerizing
- 1. Shyamoli Textile Engineering College Presentation On Mercerizing
- 2. Contents 1.Mercerization 2.Creator Mercerization 3.Mercerizing Definition 4.Objective 5.Theory 6.Types of Mercerization 7.Flowchart of mercerizing 8.Surface of cotton 9.Fiber cross section 10.Condition point for mercerizing 11.Which stage cellulose can be merceraized 12.Fabric mercerizing machines 13.Requrements of good wetting agents 14.Different steps in mercerizing cycle 15.Degree of Mercerization 16.Test of Mercerizing 17.Purpose of Mercerizing
- 3. Mercerization is a finishing treatment of cotton with a strong caustic alkaline solution in order to improve the luster, hard and other properties, was names after its discoverer, John Mercer, and has been in use for sometime. It has been seeing an increase in application recently. Mercerization
- 4. John Mercer (21 February 1791 – 30 November 1866) was an English dye and fabric chemist and fabric printer born in Great Harwood, Lancashire. In 1844 he developed a process for treating cotton, mercerization, that improves many of its qualities for use in fabrics. Creator Mercerization
- 5. It is a treatment for cotton articles and natural fibres composed by cellulose in a concentrated solution of caustic soda (300 g/l), under tension and ambient temperature. Fibre swelling and simultaneously there is a longitudinal shrinkage, modifying the morphological structure of the fibre and achieving a shinier surface, resistant to wear and washing. Mercerizing Definition : Objectives: Fig : Mercerizing Cotton
- 7. THEORY Since concentrated sodium hydroxide (operational solution that includes chemicals) is used in mercerization process, the reactions that take place with the cellulose fibers are intermolecular reactions. That is, the sodium hydroxide that is concentrated this much, penetrates inside the micelles (crystallites) and a structure called hydrate cellulose emerges. Cell – OH Cell – OH + NaOH Cell – ONa + H2O Cell – ONa + H2O 75% 25% Sodium hydroxide reacts with the hydroxyl groups inside the macromolecule in such a way that it either produces sodium cellulosate or it links to the molecules through the pulling forces. Although both of them take place in mercerization, 75% is on linking’s side through the force of pull.
- 12. THE CONDITION OR CONSIDERABLE POINTS FOR MERCERIZATION Tension Concentration of caustic soda solution. Time period. Tensile strength Wetting Agent agent Staple length
- 13. WHICH STAGE CELLULOSE CAN BE MERCERIZED After desizing After dyeing On greige goods After bleaching After scouring
- 15. REQUREMENTS OF GOOD WETTING AGENTS: *It should posses a high wetting power. *It should enable the alkali to swell the cotton fiber rapidly. * Should not be preferentially absorbed by the fiber being treated. *It should disperse perfectly. *It should be soluble in caustic soda solution. *It should not give rise to excessive foaming or turbidity in the solution or deposits on the fiber and machine parts. *It should not discolor the fiber permanently. *Its effects of mercerizing liquor should be permanent. *It must be easily removable. *It should able to reduce the surface tension of water. *It should not be injurious to the workers. *Should not interfere with the caustic recovery from the wash liquors after mercerization. *Should be available at an economical price.
- 16. Pre tensioning .Shrinking Lye tensioning Squeezing Washing and tensioning Final caustic content Different steps in mercerizing cycle
- 17. Determination of Degree of Mercerization The effect of mercerization depends on the conditions of mercerization. A quantitative assessment of the degree of mercerization is carried out mainly in three different ways i.e. variation in the mercerized product, external appearance (lustre) and internal appearance (x-ray diagram) etc. Determination of deconvolution count In this method cotton hairs are cut in large number of hair fragments 0.2 mm long. They are then mounted in liquid paraffin on a microscopic slide, and then counted the proportion of fragments free from twist on convolution during mercerization. The result is expressed as percentage and is called" Deconvolution Count". If the figure is above 20, the fabric is mercerized. The ratio of the two sets of data may be used to estimate the degree of mercerization. The disadvantage of this method is that the extent of deconvolution is influenced by the maturity of cotton and by the structure of material that is twist of the yam or weave of cloth.
- 18. Determination of swelling index Untwisting number of single yarn can give reliable means for estimating degree of swelling of cellulose in non-polar liquids such as carbon tetrachloride and benzene. Strong alkali solution and cadoxen (cadmium ethylene di amine complex of 3.6%) also causes large amount of untwisting. In this method, the yarn together with the weight (0.8 g) is hanged into the measuring cylinder containing sufficient amount of solvent as to dip the upper end of the yam. The yam is then allowed to untwist and the number of revolutions made by weight are measured for 3 min. Swelling index = (Untwisting number in solvent) / Untwisting number in water) Swelling index increases with degree of mercerization. In this method there is no necessity of untreated sample.
- 19. Benzopurpurine test Sodium hydroxide spotting test Goldthwait Red-Green test Staining test Test of Mercerizing
- 20. MERCERIZING IN SIM GROUP: Parameter: Steam cylinder= 20 Temp= 100°C Pressure = 2-2.5 pa 1th pressure = 0.21 mPa Padder= 0.21mpa 2nd pressure= 0.31 mpa Padder= 0.24mpa Caustic soda = 1L on 766gm= 50 boom 18 boom= 3000L Sometime they add mercerize oil acetic acid wetting agent Scouring caustic= 30-50g/l
- 21. 1.The main changes occurring in the alkaline treatment of cotton are:Solubility in solvents is increased; 2.The length of yarn or area of cloth is reduced; 3.Tensile strength is increased; 4.Absorption of dyestuff is increased; 5.Physical compactness of either cloth or yarn is increased; 6.Water absorption is increased; 7.Reactivity with oxygen (air) is increased; 8.Reactivity of cotton at lower temperatures is increased; 9.Sodium hydroxide (caustic soda) is preferentially absorbed during the process; 10.Luster is increased; Purpose of Mercerizing