Fiber maturity is an important character of
cotton and is an index of developments of the fibers. The maturity of the cotton
fibers varies not only between fibers of different samples but also between
fibers on the same seed. Thus a ripened full mature cotton boll contain fibers
of both mature and immature. A cotton fiber consists of a cuticlem, a primary
layer and secondary layers of cellulose surrounding the lumen or the central
canal. In the case of mature fiber, the secondary wall thickening is very high
and in some cases, the lumen is not visible. In the case of immature fibers, due
to some physiological causes, the secondary wall thickening is practically
absent, leaving a wide lumen throughout the fiber. Hence to a cotton breeder,
the presence of excessive immature fibers in a sample would indicate some defect
in plant growth, either varietal or environmental. To a technologist the presence
of excessive percentage of immature fibers in a sample is undesirable as this
causes waste, losses in processing, lowering of the yarn appearance grade due to
formation of neps, uneven dyeing etc.
The
determination of the fineness of cotton is affected by maturity of the sample.
An immature fiber will shoe a lower weight per unit length than mature fiber of
the same cotton, as the immature fiber will have less deposition of the
cellulose inside the fiber. Hence it is essential to measure the maturity of a
cotton sample in addition to the determination of its fineness., to check
whether the observed fineness is an inherent varietal characteristic or is a
result of immaturity.
Importance of
maturity:
The maturity of the fiber is
concerned with development of cell wall. The cell wall thickening is highly
sensitive to growing conditions. Adverse weather, poor soil plant, plant
diseases and pests etc., will increase the proportion of immature fiber and lead
to trouble in processing.
One of the main
troubles caused by the presence of these thin walled immature fibers is nepping.
Apart from maturity, causes like small bits or fragments of seed particles
attached to the fiber also forms neps. Neps are created during processing
starting at ginning stage. Further when rubbing of substances takes place, as in
carding, minute knots of tangled fibers are caused and the immature fibers are
more prone to this nepping effect. When fine cottons are being processed, the
danger of nepping is even more acute, since even the mature fibers are likely to
cause neps by faulty processing. In addition, the neps so formed are usually
more prominent because of their size relative to the diameter of the yarn.
Immaturity
also affects the shade after dyeing. As the response of the primary wall to
certain classes of dyestuffs is less intense, the thinner the secondary wall
lighter will be shade. Hence fine cotton tends to be lighter in shade than
coarse cotton. Apart from this the reflecting surfaces of the fibers of immaturity
is with respect to the patches being shown or the weft bars seen in the fabric
when yarn made of immature fibers or yarn spun from cotton of different maturity
is used as warp and weft. The presence of neps in a yarn will also form weak
places and therefore the average strength of the yarn will be reduced. Neps will
show up as specks in the dyed cloth. So summarizing the maturity, the following
points are noted.
- Maturity affects the quality of the yarn and
also processing. The effect of the immature fibers are seen especially in
the spinning process.
- The large number of ends downs in a ring frame
is due to the immature fibers.
- The loss in yarn strength, the dyeing troubles
are all due to the presence of immature fibers.
1. Percentage of Mature fibers , N
2. Maturity ratio , M
3. Maturity co-efficient, Mc
Methods of determination of
maturity - Read more ...
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