8/17/2019 IJFTR 28(3) 363-366.pdf
1/4
)
Indian journal of Fibre Tex tile Research
Vol. 28
, September 2003.
pp .
363-366
Short Communication
Irregularity and imperfections
in
ring-spun
yarns
R V Mahendra
Gowd
a
Department of Tex tile Technology , Bannari Amman In st itute
of
Tec hno logy, Sathyamangalam 638 401, India
Received 2 March 2 2; revised received and
accepted
6
August 2 2
Ring-spun yams
of
different
co
unt s and fibrous materi als ha ve
been studied for irregularity and impe
rf
ec
ti
ons. The irregul arity
length equations have been
develop
ed using five different cut
lengths
(10,
100
. 1000, 10000,
and
100000
mm) to
deduce
irregu larity-length indices (m and a). The values o f ' m' and
' a ' for
a
ll
the
yams
are found to be
- 0.
25 and
22.5·-29.7
r
espec
tively. The
irr
eg
ul
arity is found to be correlated highly , fairly and poo
rl
y with
thin places (-30 ), thick places (+50 ) and neps
(+200 )
respectively for various yams studied.
Keywords: Irregularity -length indices, Ring-spun yams. Yarn
imperf
ec tions,
Yam
irregu larity
Irregularity and imperfections are the important quality
attributes of a spun yarn that influence the yam
processability and fabric appearance.
The
irregularity
or unevenness
of
a yam is commonly defined as the
variation
in
fineness along its length and more
appropriately as the variation in mass per unit length
along the yam It is expressed as U or CV%. The
imperfections are frequently occurring yam faults
which include thin places, thick places and neps .
The irregularity and imperfection s
in
a spun yarn
are inevitable and their occurrence can be attributed to
either the fibre characteristics and their variation
or
an
imperfect spinning process or both.
Further, it is well known that the yarn irregularity
decreases as the
yam
cut length increases . This
information is provided readily by the variance-length
curves obtained from any evenness teste? A
thorough understanding of the irregularity [CV(L)]
along the yam and the relationship between yarn
irregularity (U ) and imperfections will be highly
useful in taking measures to control these parameters.
The present study was, therefore, aimed at
establishing an empirical equation for the irregularity
• Phone:
221289;
Fax:
0091-04295-223775;
E-ma
il
:
[email protected]
[CV(L)] along the yarn and a correlation between U
and imperfections
in
various ring-spun yarn s.
Nine differe nt types of ring-spun yarns, namely 40s
acrylic, 34s
vi
scose, 40s polyester, 49s po lyester, 57s
polyester , 30s combed cotton , 20s carded cot ton , 30s
polyester/cotton (P/C) combed and 40s PIC carded,
spun on the same set of machinery were used for the
study.
All these yarns were tested on UT3 tester for
unevenness and imperfections at a test speed
of
400
rnImin with 8 tests per yarn sample. Thin
pl
aces were
measured at three sensitivity levels, name ly -
30
,
-40 and -50 . Thick
pl
aces were measured at the
sensitivity levels of +50 and + 100 , and the
neps
were measured at
+200
level
of
sensitivity.
The variance-length curve was plotted for each
yarn sample and the irregularity va lues at different cut
lengths, namely 10, 100, 1000, 10000 and 100000
mm, were determined. By plotting the values of
logarithm of [CV(L)] against that of logarithm of L
and carrying
out
the regression analysi s of the
transformed data, the follow
in
g irregularity-length
equation was developed for each yarn sample:
Let L be the cut length of yarn in mm, and CV(L)
be the irregularity of yarn
of
cut length L If log
[CV(L)] is plotted against log L then
log [CV(L)]
=
log a + m log L
Therefore,
[CV(L)]
=
a
LIll
.. . (I)
where 'a' and ' m' are the constants, depending on the
yarn
count
and the fibre mJte
ri
al.
The
se constants are
named as ' irregularity-length indices'.
The
imperfections at different sensitivity levels
were also correlated with the yarn irregularity (U )
for all the yarn samples. .
Table 1
shows
that the values
of
irregularity-length
index ' m' are negative, indicating
th
at the irregularity
decreases with the increase in cut length. Further, the
values
of
' m' are more
or
less the same for a
ll
the
yarns studied. The average value is found to be -0.25.
Thi s indicates that the ' m' is almost independent of
type and count of yarn.
Table 1 also shows that the values
of
irregularity
length index 'a' range from 22.5 to 29.7. It is lower
for a yarn with lower irregul arity and higher for a
8/17/2019 IJFTR 28(3) 363-366.pdf
2/4
364
INDIAN J.
FI8RE
TEXT. RES
..
SEPTEMBER 2
00
3
Table I- Irregularity-
Ien
g
th
equations
Yarn Irreg
ul
arity-length
Coe
ffi
cie
nt
of
I reg
ul
ari ty-Ieng
th
equa
ti
ons
determination
(/?2)
indices
Acrylic (405)
Viscose (34s)
Polyes ter (405)
Po
ly
es t
er
(49s)
Polyester (57s)
Co lton (20s K)
Calla n (30s C)
Polyes ter/Callan (30s
C)
Polyester/Collon (40s
K)
K - Ca
rd
ed and C
-C o
mbed
Yarn
Acrylic (40s)
Viscose (34s)
Polyester (40s)
Pol yester (49s)
Polyest
er
(57s)
Colton (20s
K)
Colton (30s C)
Pol yester/Collon (30s C)
Polyester/Callan (40s K)
Cut leng
th in
mm
rCV(L)]
=
29.7 L-
0251
0.993
rCV(L)1
=
23.4
CO
253
0.999
rCV( L)1
=
24.0
L 25 1
0.997
rCV(L)]
=
24.3 L O25U
0.998
ICV( L)]
=
24.4
L
{1249
0.999
rCV(L)1
=
25 .4 L
{
1
253 0.998
ICV(L)]
=
22.8 L
-{
·
25
O
0.999
rCV(L)]
=
22.5 L
{
2
50
0.999
rCV( L)]
=
26.7 L {)250
0.999
Tah
le 2 - Actual a
nd
pred icted va
lu
es
of
irreg
ul
arity
rCV(L)1
10
I00 1000 10
000
15.7 9.2 5.65 3.2
( 16.6) (9.35) (5.25) (2.94)
12.72 7.55 3.92 2.
31
(13. 16) (7 .4) (4.16) (2.34)
13
.0
7.
65 4.39 2.5
( 13.47) (7.55)
(4 .24)
(2.38)
13.2 7.85 4.47
2.55
( 13.66) (7.68) (4.32) (2.43)
13.3 7.95 4.44 2.
51
( 13.75) (7.75) (4.37) (2.46)
13.6
8.2
4.3 2.54
( 14 .28)
(8.03)
(4 .52) (2 .54)
12.8 7.25 3.9 2. 37
( 12. 82)
(7.2 1) (4.05) (2.28)
12.55 7.3 3.85
2.29
( 12.65)
(7.12)
(4.00) (2.25)
15.0 8.5 4.73 2.59
( 15.0 I)
(8.44)
(4.75) (2.67)
Values
in
parentheses indi cate predicted irreg ularity.
a
-0.251
29.7
-0
.253
23.4
- 0.25 1
24.0
-0 .250
24.3
- 0.249
24.4
- 0.253
25.4
- 0.250
22 .8
-0.250
22.5
- 0.250
26.7
Correlmion
100000
coeff
icie nt
r)
1.4
0.998
( 1.65)
1.
25 0.999
(
1.
32)
1.25 0.999
(1.33)
1.3 0.999
( 1.37)
1.
35
0.999
( 1.39)
1.3
0.998
(1.43)
1.
25 0.999
( 1.28)
1.2
0.999
( 1.27)
1.4 0.999
( 15 0)
ya rn with higher irregu larity. Further, when
L lm m
,
the va lu e of 'a' in Eq (I) equ als [CY L)], which
represents the maximum po ssible irregularity in a
given
sp
un
yarn for
I
mm
cut length. T he very hi gh
va
lu
es
of
coeffic
ient
of
determination
2
en
visage
that a ll these em pirical eq uation s as shown in Tab le 1
are very well valid for predicting the irregularity in a
spun yarn with
diff
erent cut lengths rang in g from ]
mm to several hundred metres . This is a l
so
ev ident
from Table 2 and Fig. 1
which
show a good
association
betwe
en the predicted
and
the actual
values
of
irr
egu
larity for diffe rent cut leng ths.
Table 3 shows that in a ll the yarns, U% is hi ghly
corre
lated with thin
places
at -30% sensi ti vity leve l
fo
ll
owed
by a
good
to fair
cor
re lat ion with thin
pl
aces
at -40% and -50% se nsitivi ty level s respec
ti
ve ly.
This clearly indicates that the cause for the origin of
U% and thin places is
more
or less the sa me,
i.
e.
ma
inly the
drafting op e
ration. As reg ards thick pl aces,
the re is a fairly good correlation between U% and
8/17/2019 IJFTR 28(3) 363-366.pdf
3/4
SHORT COMMUNICATION
365
likely to influence the thin and thick places
3
.hick places at +50% sensitivity level which proves
that the source of origin of U% is partly responsible
for the occurrence of thick places . The good
association of thin and thick places with U% implies
that the factors which influence unevenness
are
also
Finally, it can be observed from
Table
3 that except
in 20s K cotton yarn, the correlation between U% and
neps
is
generally
poor
, which clearly shows th at the
causes for the origin of these parameters are largely
1 8 ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
16
14
Yarn
Acry lic (40s)
Viscose (34s)
Pol yester (40s)
Po lyester (49s)
Cotton (20s K)
Cotton (30s C)
Po lyester/Co tton (30s C)
Po lyester/Co tton (40s K)
"Sensitivity level for thin places
bSensitivity leve l for thi ck places
- 40sAcrylic-predicted
- 40sAcrylic-actllll
_ 34sVillCOsc-predicted
348VlSCosc-actllll
20S ( Cotton-predicted
20S ( Cotton-achlll
3 £
Cotton-predicted
1 3 £ Cotton-8ctllll
3
4
5
logL
2
__ 49sPolyester-predictcd
49s Polyester-actlJll
3 £
PIC-predicted
308 C P/C-actlJll
40.
K PIC-predictcd
40sK PA:-actlJll
3
4 5
Fig. 1 - Irregularity
vs
log for various ring-spun ya
rn
s
Table 3 - Correlation between U% a
nd
imperfections
U% and thin places U% and thick places
U% and
-30% (- 40%)
(- 50%)"
(+50%
)h
(+100%)6
neps (+200%)
0.84 0.83
0.79 0.51
0.10 0.38
0.97
0.94 0.78
0.78 0
1
2
0.33
0.95 0.89
0.3 1 0.3 1
0. 14 0.25
0.85
0.84 0.
13
0.61 0. 10
0. 14
0.95
0.95 0.18
0.83
0.
11
0.
71
0.93
0.92
0.65
0.50 0.20
0.
12
0.97
0.93 0.59
0.59 0.26
0.20
0.97
0.96 0.64
0.88
0.56
0.45
