Ramie fiber
| Ramie fiber | |
|---|---|
| Fiber type | |
| colour |
White |
| properties | |
| Fiber length | 60-260 mm |
| Fiber diameter | 16-125 µm |
| density | 1.50 g / cm 3 |
| tensile strenght | 500 MPa |
| Specific tensile strength | 40–70 cN / tex (dry) |
| modulus of elasticity | 44 GPa (dry) |
| Elongation at break | 2% |
| Water absorption | 12-17% |
The ramie fiber ( abbreviation : RA) or Chinese linen and grass linen , also Chinese nettle or Chinese grass , is obtained from the bast part of the stem of the ramie plant ( Boehmeria nivea ). This natural fiber belongs to the group of bast fibers .
Development and construction
The fibers make up up to 15% of the plant and are 40 to 350 millimeters long and 40 to 50 micrometers thick. Fiber bundles can reach a length of up to two meters. Ramie fibers are among the longest and strongest vegetable fibers of all.
The ramie fiber has a degree of crystallinity of 44 to 47%. Cellulose in natural fibers is partly in an ordered, “crystalline” structure and partly in a “disordered” structure. The ratio between crystalline and non-crystalline cellulose, the degree of crystallinity, has a great influence on the properties of the fiber, e.g. B. a higher degree of crystallinity leads to a lower moisture absorption of the fibers.
The fiber is particularly white, comparable to bleached cotton, and has a silky sheen that exceeds that of linen. However, ramie fibers also have in common with cotton and linen their low elasticity and susceptibility to creasing.
use
As a pure fiber, ramie makes light, silky fabrics that resemble linen . The main area of application is use as a textile fiber. However, because of its low resistance and elasticity, ramie fiber is mostly used as an admixture to other textile fibers. It increases the shine and strength of cotton fibers and reduces the shrinkage of wool fibers. Their use in this area of wool blends is, however, to be regarded as rather exotic.
In addition to textile uses, there are also approaches to use the ramie fiber in composite materials . At Cornell University , a bio-based plastic was developed that consists of ramie fibers and soy protein . Due to its mechanical properties such. B. Its good heat and sound insulation, this composite material could be used in the interiors of cars and trains, in computers and in packaging and other consumer goods.
Preparation and processing
For the preparation of ramie, the bark parts, in which the fibers are located, are first separated from the wood components (debarking or decorating). The bark strips are dried and some of them are marketed as "China grass". These still contain a fairly high proportion of 30 to 35% of pectin- like, rubber-like coating and parenchymal tissue . This is largely insoluble in water and must be removed before the fiber can be spun into fine yarn. This rubber-like coating consists mainly of xylans and arabans , which belong to the hemicelluloses .
The removal of this coating, the degumming , can therefore not be done via bacterial roasting , but requires boiling in a lye . The fibers obtained in this way consist of almost pure cellulose , are uniform, shiny, smooth, highly hygroscopic and very wet-strength. To get a white fiber, the degummed fiber has to be bleached again.
Ramie fibers are spun wet and are characterized by a very high tensile strength of 393 to 1050 MPa . The density and absorbency of the coarse fibers (25 to 30 micrometers) are similar to those of linen .
Economical meaning
Although the ramie fiber is considered to be of extremely high quality, due to its relatively complex processing, which still cannot be fully automated, it has so far not been able to compete in price with other natural fibers such as cotton , wool or linen on the textile market . In the middle of the 19th century, the ramie fiber gained a certain importance in the course of the fiber nettle industry that was developing in Europe, but was then quickly replaced by cotton and synthetic fibers .
Individual evidence
- ^ A b c Thomas Gries, Dieter Veit, Burkhardt Wulfhorst: Textile manufacturing processes - An introduction . 2nd, revised and expanded edition. Carl Hanser Verlag, Munich 2014, ISBN 978-3-446-44057-9 , p. 43
- ↑ a b c d R. R. Franck: Overview . In: RR Franck (ed.): Bast and other plant fibers , Cambridge / Boca Raton, 2005, ISBN 1855736845 / ISBN 0849325978 .
- ↑ a b c W.D. Brouwer: Natural fiber composites in strcutural components: Alternative applications for sisal? .
- ↑ Anton Schenek: natural fiber lexicon . Deutscher Fachverlag, Frankfurt am Main 2001, ISBN 3871506389 , p. 159
- ↑ Kim L. Pickering (Ed.): "Properties and performance of natural-fiber composites", Woodhead Publishing Limited, Cambridge, 2008, ISBN 978-1-84569-267-4 .
- ↑ a b c G. Holzmann, M. Wangelin: Natural and vegetable building materials: raw material - building physics - construction . Vieweg + Teubner, Wiesbaden, 2009, pp. 197-198, ISBN 978-3-8351-0153-1 .
- ↑ H.-P. Fink and S. Fischer: Cellulose processing - environmentally friendly technologies on the advance , practice of natural sciences - chemistry in school 54, 2005, No. 7, pp. 18-25.
- ↑ S. Kalia, B. S. Kaith, I. Kaur: Pretreatment of natural fibers and their application as reinforcing material in polymer composites: A review . Polymer Engineering and Science 49 (7), pp. 1253-1272, ISSN 1548-2634 .
- ↑ Natural Fibers: Ramie. On the FAO International Year of Natural Fibers 2009 website .
- ^ TO Netravali: "Green" Composites from Cellulose Fabrics & Soy Protein Resin , National Textile Center Research Briefs, June 2002, pdf .
- ↑ F. Denningerstrasse, E. Giese: fashion and textile Lexikon, Band 1, A-K . Deutscher Fachverlag, Frankfurt am Main, 2006, ISBN 3-87150-848-9 .
- ↑ R. Koslowski, M. Rawluk, J. Barriga-Bedoya: Ramie. In: Robert Franck (Ed.): Bast and other plant fibers . Cambridge / Boca Raton, 2005, pp. 207-227, ISBN 1855736845 / ISBN 0849325978 .