4.YARNS
AND FIBRES
Basic definitions
Yarn number
The yarn number is a measure of the
linear density of the yarn. It can be expressed in various ways in terms of
direct or indirect or indirect system. In the direct system, the yarn number is
the weight per unit length of a yarn and in the indirect system it is the
length per unit weight of yarn.
Count
It is a measure of the linear density of yarn considering length of a
yarn in one lb. The unit of length is 840 yards.
Ex: Yarn of 840 yards weighing
one lb is 1s count and yarn of 8400 yards weighing one lb is 10 s
count.
Tex
It is a measure of the linear density of yarn considering weight in grams
in a thousand meters length of the yarn. The unit of weight is one gram.
Ex: Yarn weighing one gram in a length of thousand meters is one Tex and yarn weighing 5
grams in a length of thousand meters is 5 Tex.
Denier
It is a measure of the linear density of yarn considering weight in
grams in a length of 9000 meters. The unit of weight is one gram.
Ex: Yarn weighing one gram in a length of 9000 meters one denier and
yarn weighing 10 grams in a length of 9000 meters is 10 denier.
Yarn numbering systems:
Count = length /
weight.
Metric (Nm) count = length in km / weight in kg
English (Ne) count = length in 840 yards / weight in pounds
French (Nf) count = length in km / weight in half kg
Denier (Td) = weight
in grams x 9000
Length in meters
Tex unit = weight in grams / length in km
Conversion factor:
To convert Nm to Ne – multiply by 0.5905
To convent Ne to Nm – multiply by 1.6934
To convent Nf to Nm – multiply by 2.0
To convent Nm to Tex
– divide 1000 by Nm
To convent Tex
to Nm – divide 1000 by Tex.
To convert Td to Nm – divide 9000 by Td
To convent Nm to Tex
– divide 9000 by Nm
Count calculations in Tex
system:
Count in Tex system = weight in grams / length in kms
= weight in grams
length in meters/1000
= 1000 x Weight in grams
Length In Meters
Length = weight in grams
Count
Or weight in
grams x 1000
Count
Weight = count x length in Kms
Or 1000 x
count x length in meters
Conversion from indirect system to universal Tex system:
Cotton (English) 590.5
Spun silk and spun rayon staples 590.5
Metric 1000
Linen (wet spun) 1653
Worsted 885.8
Woolen Yorkshire skein 1938
Required count = conversion factor
Known count
Conversion from direct systems to universal tex system:
Silk, denier (metric) 0.111
Silk dram 1.938
Jute, spyndle 34.45
Flax spyndle 34.45
Woolen, Aberdeen 34.45
American grain 3.543
Required count = known count x conversion factor
The resultant count of two yarns of counts say ‘x’ and ‘y’ are
given by
1
1
+
1
+
1
x y
The resultant count of three threads i.e say one thread of count
‘x’, two ends of count ‘y’ and three ends of count ‘z’ is given by
1 +
2 + 3
x y
z
The resultant count of yarns of different fibres twisted together
is as follows
Example: cotton
fibre of count x
Worsted fibre of count y
Rayon fibre of denier z
The worsted and rayon yarn count have to be converted into cotton counts
Worsted = unit of length in worsted x worsted count
Unit
of length in cotton count
i.e. 560 x X _____________ (a)
840
Denier = 9000x1000x1.1 ______________ (b)
2.2 x denier x
840
Therefore count is
1 + 1 +
1
cotton yarn count
a b
------------------------------Prepared
by K.A.Aravindhan------------------------------------
Yards/lb for 1s denier = Yards/hank in silk x denier per ounce x
ounces per lb
Diameter of fiber in microns = 2000 Ö A
Ö Bp9000
where A – fibre denier
B – fibre
specific gravity
Or 20 Ö denier___________
Ö 3.14 x specific gravity
Number of fibres per cross section
= 53.15 x sum of (%
of each denier)
denier of
each fiber
________________________________
Yarn count
to be spun
Fibre maturity ratio = (Normal
fibres – dead fibres) + 0.7
200
Maturity coefficient = N
+ 0.75T + 0.45D
100
where N – normal fibre
T – thin
walled or half mature fibres
Spinning Limit =
5315 
Denier of fibre x actual fibres per cross section
Neps/100 sq. inches of web = 1.531 – log (34-N) x 100
0.434
Where N-number of
cells containing neps
Spinning value of cotton = 78.2Y-24.8
Where x – mean fibre
length in inches
Y- mean
fibre weight / inch (106 oz)
Formula to predict spinning value from fibre properties
N=71.6X1 - 70.8 X2 – 20.8
X3 + 17.9 X4 + 0.037 X5 + 4.4 X6 14.1
Where N – highest standard warp count
X1
– fibre length (inches)
X2 – Fibre
weight / inch (10-6 OZ)
X3 – Ribbon
Width (10-3 inch)
X4 – Fibre
strength (OZS)
X5 – Fibre
convolutions
X6 – fibre
rigidity (OZ/inch2 x 10-6)]
Standard fibre fineness = measured fineness
Maturity ratio
Nep Count = N x hank of sliver
x card width in inches
0.12
40
40
or 21 x N x hank of sliver x card width in inches
100
N-neps / 100 Sq.
inches of web
Cleaning efficiency % of blow room = trash in mixing – trash in
lap x 100
Trash in mixing
Cleaning efficiency %at card =
trash in lap – trash in sliver x 100
Trash
in lap
Comber fractionation index =
short fibre % in comber sliver x 100
Short fibre % in sliver lap
Diameter of yarn in inches =
1 _________
(cotton & spun silk) 0.9Ö count x 840
= ____1 ________
0.9 Ö Yards/lb
_____________
Threads/inch = Ö yards/lb
– 10%
________
=
0.9 Ö yards/lb
______
= 26.1Ö counts
Diameter of yarn in inches =
1 ___
(worsted ) 0.9Ö yards/lb
_____________
Threads/inch = Ö yards/lb
– 10%
Nep index = neps per
grain in lap – neps per grain in sliver
Neps per grain in lap
Yarn strength index = corrected standard sequence yarn CLSP
(YSI) corrected Shirley
miniature CLSP
CLSP – count lea strength product
Yarn breaking strength
= 1600 (1+0.11x + 0.01y )
(carded yarn)
where x – difference
in staple in 1/16 inch, above or below 1 inch
+ sign
where staple is more than 1 inch
-
sign when staple is below 1 inch
y – difference in count above or
below 28s
+ sign when it is above 28s
-
sign when it is below 28s
The irregularity of random arrangement of fibres is given by the
formula
U = 85
%
Ö F
U – arithmetic
mean of all deviations from the average thickness
F – average number
of fibres per cross section
Relation between CV and U
CV = 5/4 U
U = 4/5 CV
Formula for yarn strength prediction
S2 = N1S1
– (N2 – N1)C
N2
Where N1
is known count
S1 is known strength
N2 is new count
S2 is new strength
C is a constant the value of which is 35+0.7 (24 – N2 )
-sign when N2
> 24
+sign when N2 < 24
The above formula is used for yarn strength prediction of a
particular count when the strength of another count from some cotton is known.
Expected least PMD = 0.656 (count x fibre fineness)
Degree of perfection = Expected PMD x 100
Actual
PMD
Pressley strength conversion
At 0 inch gauge, grams per Tex
= 5.308 x PI0
At 1/8 inch gauge , grams per Textile = 6.759 x PI1/8
PI – pressley index
Grams per Textile = lbs per square inch
2161
------------------------------Prepared
by K.A.Aravindhan------------------------------------
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