Mercerization of cotton
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John Mercer discovered in 1791 that cotton fabric shrinks when exposed to a sodium hydroxide (NaOH) solution. In 1850, he patented the mercerization process, which increases the strength and dye absorption of cotton by applying NaOH under tension. However, fabric shrinkage prevented commercial adoption until 1895 when German patents applied tension during both NaOH treatment and washing, eliminating shrinkage and allowing commercial production of mercerized cotton yarn and fabric.
Mercerization of cotton
- 1. Mercerization of cotton John Mercer 1791-1866 British Chemist Expts on measurement of viscosity of solutions of different concentrations. Tried to filter the solution of NaOH 45-55 deg. TW (Unit of viscosity, approx. twice the %conc.) through cotton fabric Observation Shrinkage in the area of fabric i.e. reduction in dimensions of fabric in width and length direction. Left expts. Till 1849
- 2. Mercerization of cotton 1850 patented process under the name Mercerization Claims Shrinkage in the area of cloth Increase in strength Increase in hygroscopicity Increased capacity for dye absorption Preferential absorption of NaOH Increased action at lower temperature Possible soda cellulose formation These basic claims are valid even today
- 3. Mercerization of cotton Main drawback: Fabric shrinkage Commercial loss: Decrease in length and width of fabrics No body showed commercial interest Process did not become commercial till the death of Mercer in 1866
- 4. Horace Lowe Horace Lowe 1869-1930 British chemist Read the patent of Mercer 1889 Started working to remove the problem of shrinkage on tretment with concentrted NaOH solutions Thought of applying tension during NaOH treatment Not only reduced shrinkage the fabric acquired lustre Patented the process in 1890
- 5. Thomas and Prevost 1895 two German patents Application of tension during NaOH treatment and during washing to remove NaOH The process was commercialized in 1895 Initial experiments on fabric Later process developed for yarn mercerization in hank form First German developed for mercerization of hank on commercial scale Since 1895 hank mercerization and fabric mercerization processes are used on commercial scale through out the world
- 6. Effect of NaOH concentration Behaviour of cotton fibre (Microscopic study) Upto 15deg. Tw NaOH No change 16-18 deg. Tw Incomplete untwisting 26 deg.Tw Rapid untwisting 35 deg. Tw Un twisting followed by swelling 40 deg Tw and above Untwisting and swelling together
- 7. Untwisting of cotton fibre in NaOH solution
- 8. Effect of twist (tpi) on deconvolution count and cotton variety Deconvolution count Twist 12 20 35 45 Deconvolution 69 58 53 30 Count Cotton variety Deconvolution counts after mercerization Cotton Yarn Fibre Uppers 79 82 Texas 45 71 Zaria 28 56 Deconvolution count decreases with decrease in fibre maturirity
- 9. Effect of NaOH on cross section of cotton
- 10. Changes in cross section of cotton on treatment with NaOH 18%
- 11. Lusture and Staple length Cotton Staple length Lusture Lusture Unmerc Merc Mako 22 mm 25.3 70 Luisiana 18 17.8 39
- 12. Swelling in alkaline solutions % swelling %Alkali 97 9.5 LiOH 78 18 NaOH 64 32 KOH 53 40 RbOH