Properties of cotton fibres considered by spinner
Yarn
The following properties of cotton fibres are considered for cotton spinning
fibre
length
:
The
average length of spinnable fibre is called staple length. Staple length is one
of s 1. F important fibre characteristics. The quality, count, strength etc. depend
on the staple length of fibre.
Fibre
length influence:
.
1.
Spinning limit .
2.
Yarn strength.
3.
Yarn evenness
4.
Handle of the product .
5.
Luster of the product .
6.
Yarn hairiness .
7.
Poductivity
2.
Fibre fineness:
Fibre
Fineness is one of the most important parameter determining the yarn quality
characteristics. Fibre fineness influences the number of fibres in the cross
section of yarn
Thirty
fibres are needed at the minimum in the yarn cross section but there are
usually over 100. One hundred is approximately the lower limit for almost all
new spinning process. This indicates that fineness will become more important. Fibre
fineness influence primarily
1. Spinning limit
2.
Yam strength,
3.
Yarn evenness
4.
Drape of the fabric product .
5.
Handle .Luster, .
6.
Yarn fullness, .
7.
Productivity Evenness is measured in
8.
Micronaire value (MIC)
Rating
of MIC value –
MIC value Fineness
1. Up
to 3.1 → very
fine
2. 3 to 3.9 → fine
3. 4.0
to 4 9 → medium
4. 5.0 to 5.9 → slightly
5. 5.9
to above → coarse
3. Maturity:
The
maturity of cotton is defined in terms of the development of cell wall. A fully
mature fibre
has
a well developed thick cell wall. On the other hand, an immature fibre has a
very thin cell. The fibre is to be considered as mature fibre when the cell
wall of the moisture - swollen fibre represents 50-80 % of the round cross
section, as immature when it represents 30-45 % and as dead when it represents
less than 25 %
Immature
fibre leads to:
1. Nepping.
2. Loss
of yarn strength
3. Varying
dye ability
4. High
proportion of short fibres
5. Processing
difficulties mainly at the card
6. Mature
fibre↑ Dye absorb↑
7. Immature
fibre ↓ Dye absorb↓
4 Fibre Strength
Toughness of fibre has a direct effect on yam
& fabric strength
Fibre
strength↑ , Yarn & Fabric strength↑
Very
weak cottons tend to rupture during processing both in blow room& carding,
creating short fibres & consequently deteriorate yarn strength &
uniformity. The following scale of value is used
1.
Below to 70 % → weak
2.
70 % to 74 % → fairly strong
3. 75 % to 80 % → medium strong
4. 81 % to 86 % → strong
5.
87 % to 92 % → very strong
6. 93 % & above → excellent
5. Fibre cleanness:
In addition to usable fibres, cotton stock
contain foreign matter or trash or foreign material of various kinds:
A.
Vegetable matter:
Husk portions, Seed fragments. Stem fragments, Wood fragments
B.
Mineral material: Earth, Sand, dust, coal
C.
Others: Metal
fragments, Cloth fragments, packing materials
Foreign matter causes:
Foreign matter causes:
(i)
Drafting disturbance
(ii)
Yarn breakage.
(iii)
Filling up of card clothing
(iv)
Contaminated yarn
Accepted
the range of foreign matters to the Bale-
A. Up to 1.2 % → very
clean
B. 1.2 % to 2.0 % → clean
C. 2.0 % to 4.0 % → medium
D. 4.0 % to7.0 % → dirty
E. 7.0 & above → very
dirty
6. Color
Color is particularly
important as a measure on how well a yarn or fabric will dye or bleach
Instrumental techniques for determining the colour of the sample have only now
reached the Industry. I measurement of colour provides reasonably accurate
results of average reflectance & yellowness in a sample
