MODELS AND METHODS IN MODERN SCIENCE
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CHEMICAL COMPOSITION AND STRUCTURE OF WOOL FIBER
I.Т.Abdullazizova
Graduate student of Fergana State University
O.M.Nazarov
Associate Professor of Fergana State University
https://doi.org/10.5281/zenodo.14292439
Wool has a very complex chemical and physical structure, which
corresponds to high natural fiber properties. Wool is one of the most amazing
materials and a design masterpiece that can never be replicated in a factory.
Wool is a complex, natural and biodegradable protein fiber that can be
regenerated and recycled. It has established environmental benefits and this is a
natural fiber grown without the use of any herbicides or fertilizers.
The composition of raw wool varies greatly due to many complex factors.
An important component is keratin. Wool differs from other natural fibers due
to its high sulfur content. The composition of raw wool is as follows: keratin -
45-75%; fat - 5 - 15%; humidity - 10-12%; milk - 2 - 12%; sand and dust - 4-30%
and vegetables - 0-5%[1].Wool fibers grow in small bundles called "sheaths"
containing thousands of fibers. Wool fiber is so flexible and elastic that it can be
twisted and bent more than 30,000 times without risk of breakage or damage..
Each wool fiber has a natural elasticity that allows it to be stretched by a third
and then spring back into place. As a biological product, wool mainly consists of
45.2% carbon, 27.9% oxygen, 6.6% hydrogen, 15.1% nitrogen and 5.2% sulfur.
Wool is estimated to contain more than 170 different proteins. These are not
evenly distributed along the fiber; proteins of different structures are located in
certain regions. This heterogeneous composition is responsible for the different
physical and chemical properties of different regions of wool.
- Keratins, which
are fibrous proteins, make up 91% of wool. Amino acids are the building blocks
of
-keratins. Keratin in wool is called "hard" keratin. This type of keratin is
insoluble in water and is very resistant[2]. Keratin is an essential, insoluble
protein that consists of eighteen amino acids. The amino acids in wool are
cysteine, aspartic acid, serine, alanine, glutamic acid, proline, threonine,
isoleucine, glycine, tyrosine, leucine, phenylalanine, valine, histidine, arginine
and methionine.. Among these amino acids, cystine has the largest amount,
which gives the hair a lot of strength. The molecular structure of wool fibers is
like a spiral, which gives wool flexibility and elasticity. The hydrogen bonds
connecting the adjacent coils of the helix have a strong effect. There are several
micro air pockets in the wool that hold the air. Air pockets have excellent
separation properties, making wool fibers ideal for heat protection. The α-helix
MODELS AND METHODS IN MODERN SCIENCE
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of wool is held together by weak hydrogen bonds between amino acids above
and below other amino acids in the helix. In wool, individual polypeptide chains
join together to form proteins through various covalent (chemical bonds) and
non-covalent physical interactions called cross-linking. The most important
crosslinks are sulfur-containing disulfide bonds, which are formed during fiber
growth through a process called "keratinization.". These bonds make keratin
fibers insoluble in water and more resistant to chemical and physical effects
than other types of proteins. Disulfide bonds are involved in chemical reactions
that occur in the "coating" of fabrics during the finishing process. In this process,
the disulphide bonds are rearranged to give wool fabrics smooth drying
properties, so that ironing is not required after washing. Another type of cross-
linking is an isopeptide bond formed between amino acids containing acidic or
basic groups. In addition to chemical crosslinks, some other types of interactions
also help to stabilize the fiber under wet and dry conditions. They arise from
interactions between side groups of amino acids that make up wool proteins.
Thus, hydrophobic interactions occur between hydrocarbon side groups; and
ionic interactions occur between groups that can exchange protons[3]. These
ionic interactions, or "salt bonds" between acidic (carboxyl) and basic (amino)
side chains, are the most important of the non-covalent interactions.. The most
important of the non-covalent interactions is the ionic or "salt bond" between
the acidic (carboxyl) and basic (amino) side groups. The amphoteric behavior of
the carboxyl and amino acids in wool is also important because they give wool
its amphoteric or pH buffering properties. This is its ability to absorb and desorb
acids and alkalis. Ionic groups also control the dyeing of the fiber by interacting
with negatively charged dye molecules.[3].
Literature:
1. Rippon, J. A.(1992) The Structure of Wool; Chapter 1, In: Wool Dyeing , Lewis,
D .M. (Ed.), Bradford (UK): Society of Dyers and Colourists.
2. Leeder, J . D. (1984) Wool – natur e's wonder fibre , Ocean Grove, Vic.:
Australasian Textiles Publishers, Morton, W .E. and Hearle, J.W .S., [1993]
Physical Properties of Textile Fibres, 3rd Ed., Manchester, UK.: The Textile
Institute.
3. Rippon, J. A. et al, (2003) Wool, in Encyclopedia of Polymer Science and
Technology , New York : Interscience Publishers.
