Sources of cellulose fibre
In the complex designs and structure of the
plants, nature has used fibres as the basis of strength providing skeleton. Bundles
of fibres bound together by natural gums or resins run through the roots,
stems, fruits and leaves of plants. These strands of fibres are associated with
varying amounts of other natural substances such as lignin, pectin,
hemicelluloses, gums, waxes and colouring matters. The total carbohydrate
material is usually designated as holocellulose. The amount of these associated
substances 8 and the ease with which fibres can be separated from them
determine the utility of the fibre as textile material: These fibres can be
classified by its reference to the part of the plant from which they belong. The
important sources of cellulosic fibres are mentioned below:
Seed fibre
The seed hairs like cotton contains cellulose
with very less non- cellulosic substances ( 4-12 % ) .This makes purification
most simpler than for most of other cellulosic fibres. Other seed fibres are
kapok and bombax cotton .These fibres contain 55-65 % cellulose
Bast fibre
The bast fibres are long fibres of the outer
bark of various plants which strengthen the stem of the plant. They include
flax, hemp, jute, ramie, kenaf, sunn etc. The fibres are integrated with
natural gum in the plant structure. The fibres are separated by removal of the
gums and the process is generally known as retting
Leaf fibre
Many
of the cellulosic fibres like sisal hemp, Manila hemp are also obtained from
the leaves of the plants. The fibres extend longitudinally the
full-length of the leaf and contribute strength to the leaves. The fibres are buried in tissues of the leaves and can be separated from the tissue by scrapping since there is no bonding between the fibre and the tissue. This process is known as 'decortications.
full-length of the leaf and contribute strength to the leaves. The fibres are buried in tissues of the leaves and can be separated from the tissue by scrapping since there is no bonding between the fibre and the tissue. This process is known as 'decortications.
Fruit fibre
The
husks of Coconut , betelnut and palmnut which protect the fruit for development
can be processed and utilized as fibres. After removaľ'of the fruit, the husk
can be extracted, retted and processed.
Source of cellulose
Cellulose
also occurs in many materials as non-fibrous form. The substances containing
cellulose are as follows
wood
Wood is the most widely used cellulose material. It is found all over the world. Generally there are two types of wood:
(1) Hard wood and
(2) Soft wood.
The
hard woods are composed of closely packed cells with thick walls. On the other
hand, the soft wood are usually composed of large cells with thin walls. Woods
are mainly cellulose, lignin and hemicellulose. There are three main chemical
processes by which cellulose can be extracted from the wood. Those are:
(a) The sulphite process,
(b) The sulphate process and
(c) The soda process.
The
soda process is generally used for hard woods
Grass
Another
important source of cellulose is grasses and straw. Sabai grass, espato grass,
cereal straw, rice straw and wheat straw etc are the main sources of cellulose.
Agriculture Wastes
Cellulose
is the major constituent of the cell wall of plant life. So the residual wastes
from utilized plants form a huge potential source of cellulose. The crushed
stalk of sugar cane, corm cubs, rice halls, grains and seed hulls, soybean
stems, sunflower stalks, castor bean stalks, nut shells etc are considered as
sources of cellulose
.
Cellulose from non vegetable source
Cellulose is also found in animal and
mineral kingdom. It occurs in fossil Woods, peat, lignite, mineral cellulose
(sapperite) and animal cellulose like tunicin.