Mercerization
The mercerisation ( mercerisation ) is a finishing process for cotton that by Englishman John Mercer was developed in the mid-19th century. When filtering caustic soda through a cotton cloth, he noticed that the fabric swelled up and then had significantly different properties. The process can also be used for other natural fibers such as jute , ramie or linen , but then has slightly different effects on the fibers than with cotton fibers.
During mercerization, the cotton fibers are exposed to concentrated caustic soda under the action of tensile stress. The fibers swell, the cross-section changes from kidney-shaped to round and the length of the fibers is reduced by up to 25%. These structural changes lead to
- silky, washable shine,
- better dyeability, requires less color,
- higher strength and
- better dimensional stability .
The improved properties are based on a change in the crystal structure of the cellulose . In the case of natural cellulose, the individual polysaccharide chains within the molecules as well as within the molecular layers are stabilized by hydrogen bonds . Only Van der Waals forces act between the layers . Mercerization leads to recrystallization. Now there are also hydrogen bonds between the layers.
Technically, the achievable properties are determined by the mercerization process used (hot or cold mercerization, dry-on-wet or wet-on-wet process, roller or vacuum impregnation) and the influencing parameters of fabric tension, dwell times and the sodium hydroxide concentration.
The process increases the quality of the textiles, but is very costly. Therefore it is only used on high quality textiles.
It was used by Horace Arthur Lowe around 1890 as a method for producing shine and introduced into industry in 1895 by the “Thomas & Prevost” company in Krefeld .
Fabric made from mercerized cotton is also known by the French name “Fil d'écosse”, meaning Scottish threads . Sometimes wool treated with the Hercosett process is also referred to as “mercerised”.
Viscose production
The alkaline swelling is a preparatory process step in the production of viscose fibers from cellulose.
Individual evidence
- ^ Brockhaus ABC chemistry in two volumes. Brockhaus Verlag, Leipzig 1965, p. 861.
- ^ Ryszard M. Kozlowski: Handbook of Natural Fibers. Volume 2: Processing and Applications , Woodhead, 2012, ISBN 978-1-84569-698-6 , p. 124.
- ↑ Nishiyama et al .: Crystal Structure and Hydrogen-Bonding System in Cellulose Iβ from Synchroton X-Ray and Neutron Fiber Diffraction. In: Journal of the American Chemical Society. 2002, Vol. 124, pp. 9074-9082.
- ↑ Langan et al .: A Revised Structure and Hydrogen-Bonding System in Cellulose II from a Neutron Fiber Diffraction Analysis. In: Journal of the American Chemical Society. 2003, Vol. 125, pp. 14300-14306.