Mercerising of Cotton
History
The process was devised about 1844 by John Mercer who treated cotton with solutions of 55–65 ° Twaddell scale (50%) sodium hydroxide followed by washing. Mercer observed that the treated fabrics shrank, had increased tensile strength, and an increased affinity for dyes. In the original process of Mercer, no tension was applied. The product was termed felled cotton, a nod to the process of fulling in woven wool fabric. Mercer regarded the increased affinity for dyes as the most important technical aspect. Mercer also experimented with sulfuric acid and zinc chloride solutions and discovered the parchmentizing effect of sulfuric acid.The silk-like luster now commonly associated with mercerizing is produced by tension and was discovered by Horace Lowe in 1890. Process
Preatment with sodium hydroxide destroys the spiral form of the cellulose with formation of alkali cellulose, which is changed to cellulose hydrate on washing out the alkali. Caustic soda concentrations of 48% to 50% are used. Effective mercerization requires the use of wetting agents.
The improved lustre of mercerised cotton is due to the production of nearly circular cotton fibres under tension. Another characteristic feature is the untwisting (deconvolution) of the cotton hair. In dry mercerization, the process is carried out while drying the fabric on a stenter. Recipe : Caustic Soda 50% :280 gpl to 320 gpl Mercerizing Wetting (Mindyne MR Conc.) : 1% Contact Time : 1- 3 min. (depend on quality of fabric) 1st Tanks(Caustic Solution ) è 2nd Tank Washerè3rd Tank Washer Out for Rolling put for 8 to 12 hrs Shrinkage Should be at least 10% to 20% after caustic Pad Benefit of Mercerising- To increase silk-like luster.
- To improve moisture regain/content.
- To increase dye absorbency.
- To improved strength and elongation properties.
- To increase smoothness and hand feel is good.
- To stabilized the strength of yarn or fabric.
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