Indi an Journal of Fibre & Textile Research
Vol. 28, March 2003, pp. 23-28
Direct determination of yarn snarliness
A Primentas"
Schoo l of Textile Industries, The University of Leeds, Leeds LS2 9JT, UK
Received 5 October 200 1; revised received and accepted J J March 2002
The formation of snarls that takes pl ace in the yarn s in post-spinning processes, such as w indin g, warpin g, weavi ng and
knitting, has been studied. Th is de fect is due to the excessive ya rn tw ist liveli ness (tors ion al buckling) and causes g reat
trouble to thc manufac ture rs of yarns and fabric s. Biased testin g techniques are used for the measurement of this defect. A
snarlin g testing apparatus PRIANIC and an unbiased testing techniq ue have been developed and are reported. Th e
inv estigati on of factors such as yarn package form, yarn twist factor, tim e elapsed between production and processing stages
of yarns and yarn condi ti oning show the significant role th ey play in the reduction of yarn snarliness.
Keywords: Knitting, Snarliness, Twist li ve liness, Warpin g, Weaving, Windin g, Yarn package, Yarn twist factor
1 Introduction
The twisted shape of the fibres forming a yarn
blings to the fore two of their main physico-mechanical
properties: torsional rigidity and torsional buckling.
The higher the torsional rigidity, the stronger is the torsional buckling effect, also known as yarn twi st liveliness. It is the tendency of a newly spun yarn to untwi st
spontaneousli , a detrimental yarn characteristic having two representatives - the snarliness that occurs in
the yarns and the spirality that appears in knitted fabrics. On the contrary, the crepe phenomenon, appears
in special woven fabrics, is considered as a beneficial
result of the yarn twist livelin ess.
Yarn twist liveliness is affected by the twi st factor,
yarn fineness 2 and retractive forces , which, in turn, are
determined by the torsional and bending stresses in the
fibres 3, and the torque generated during yam twisting.
The latter is constituted by three components, viz. tor4
sion, bending and tension of the fibres , whereas its
level depends on the degree of fibre migration that
takes places. The twist liveliness of fal se-twisted and
set yarns depends on their structure and, in particular,
s
on the properties of the helical parts of their filaments .
twist direction 6 . Newly produced yams exhibit a great
tendency to untwi st when freed from restraint. When
such a yarn is prevented from untwisting, by being held
at both ends approaching each other, it forms an arc.
The nearer to U-shape this arc gradually comes, the
easier is snarl form ation (Fig. 1), whereas in highly
twisted yarns, snarls are formed very fast before an arc
appearance (Fig. 2). Recent research 7 has shown that
the torque required for a yarn to snarl is independent to
the yarn twi st level. Snarls appear in thinner yarn parts
where twist accumulation occurs and/or in a likel y part
of the yam when the numerical difference (yarn weight
minus untwi sted stress) has a negative value.
M any problems originate from the yarn snarliness
and appear in post-spinning yarn processes. In yarn
w indin g , a snarly yarn might be accumulated behind
the fin ger guide (knife) of an electronic slub catcher,
res ulting in yarn breakage and worsening its qu ality.
1.1 Snarl
The snarl is due to yarn torque and takes place during the torsional buckling effect, where the yarn retires
into itself and simultaneously is twisted in the opposite
Present address: Department of Textile Engineering, Faculty of
Applied Technologies, TEl of Piraeus, 250 Thivon & P. Ralli,
Athens 12244, Greece
Phone: + 3-2 10-4515137; Fax: + 3-2 10-4122977 ;
E-ma il: aprim@ teipir. gr
a
Fig . I- Snarl formation of a normally twi sted ya rn
24
INDIAN 1. FIBRE TEXT. RES. , MARCH 2003
!
j
!
~-
----------
I
----~~-
...........
- -.---
........
~.
-- -.-
-- - .
Fig.2-S na rl fo rmati o n of a hi g hl y twisted ya rn
midd le of a known length of yarn. As soon as the two
yarn ends are brought together, a loop (s narl ) is
formed as rotated unti l reac hin g the immobility state.
The number of turn s of the loop and/or th e
measurement of the di stance betwee n the two yarn
,s
ends .' 6 give the yarn snarlin ess level. The drawbac k
of th ese methods is th e constraint of the snarl
formation in a specific yarn pl ace, a fact that does not
permit the draw ing of true conclusions about the
objecti ve snarling tendency of the yarn s. Furthermore,
there is confusion abo ut the mass of the hanged object
and the length of the yarn sa mpl es. Also , th ere is no
mention about yarn pretension.
Al l th e above high lighted th e necess ity of using a
simple new method and an apparatus for the
meas urement of snarliness, overcoming most of the
sources of errors and shortcomings of th e earl ier
meth ods. Therefore, in the present work , snarl ing
testing apparatus PRIANIC and an unbi ased test ing
technique have been developed and are reported.
a
2 Materials and Methods
2.1 Sna rlin g Testing Apparatus PRIANIC
Due to lack of tensions, the snarl s are fo rmed in single
yarns as they are withdrawn over the top of bobbins
durin g the fo lding-twisting processes and especially
in two-for-one twisting where thi s problem becomes
more seriou s. In weaving, snarl s in weft yarns appear
when the shuttle returns to the shed from the box.
Some of these snarl s are entrapped into the cloth and
do not open out even wh en th e weft is sub seq uentl y
tensioned as picking proceeds, mak ing necessary th e
cloth mending for their remova l. As the hanks made
from hi ghl y twisted yarns are removed from the reel
swift , th ey shrin k and fo rm numerous snarl s, causing
great troubl e during their positioning on the rods
(buttons) of the hank-dyeing machi ne. Moreover,
durin g the winding of these dyed yarn hanks to co nes,
the formed snarls can cause snatching, tension peaks
and yarn breakage .
It is a virtue for a yarn, with its op timum twist
factor, to have the minimum snarlin ess level that ca n
be achi eved by several ways such as storin g9 at
adequately high temperature and rel ativ e humidity
(70-75 %) or by steaming lO th at resu lts in a fast yarn
relaxati on.
1.2 Existing Methods for Testing Yarn Snarli ness
Several wo rkers3.11. 14 , in an endeavour to meas ure
yarn snarliness, have described various methods that
are more or less based on the sa me principle. In th ese
meth ods, a light mass object is suspended fro m th e
The apparatus shown in Figs 3 and 4 cons ists of a
base where two stands are firml y fixed. A th readed
rod with two ball bearings is placed on th e top of
these stands. A motor on the base drives the threaded
rod where beneath the latter there is a scale with
li near metre (l00 cm). On th e right side of the
apparatus, a movable part ( J) with clamp j aw and a
pointer is in contact with th e threaded rod , whereas a
stationary j aw (2) with a special yarn prete nsion
system ex ists on the left side. The pretension system
cons ists of an adjustable co unterbalance and a
graduated rod (0-200 g) that is based on the TEX
sys tem , with tension uni t of tex/2 ± 10% g.
2.1.1 Principle
The operation principle of the dev ice is simp le. A
yarn length of one metre is clamped on the two jaws
of the dev ice. The mo vab le part approaches th e
stati onary one as it is driven by the rotat ing threaded
rod. The yarn figures a U-shape loop and according to
its twi st li ve liness, a snarl is fo rmed.
2.1.2 Testing Procedure
The devi ce is set to its ini tial cond itions. The
movable part (1) is returned to the ri ght side of the
device, where the pointer indicates th e va lue 100 on
the scale. As the linear density of the yarn is known,
the appropri ate adju stmenr is made on th e pretension
system. After discardin g a substa nti al quantity of yarn
PRIMENTAS: DIRECT DETERMINATION OF YARN SNARLINESS
25
Fig.3-S narlin g testing apparatus "PRIANIC"
Movable Jaw (1)
Guide
Threaded Rod
\
Pulley·
/
Fig.5-Effect of yarn unwinding method on yarn twi st (a-overend, b-s ideways, and c-under-end)
Yarn Specimen
Scale
Pointer
Fig.4-Schematic presentation of the snarlin g testing apparatus
"PR1ANIC"
from a bobbin, one metre yarn specimen is fastened in
the grip of the stationary j aw (2) wh ile holding the
other end of the yarn to prevent the loss of twist. The
yarn is stretched until no contact of the graduated rod
pointer of the pretension system can be detected and
fastened in the grip of the movable part (1) . By
switching on the motor, the threaded rod rotates ,
forcing the movable part to move towards the
stationary jaw. Thu s, the yarn becomes loose and
figures a U-shape loop. By the time the first snarl is
formed, the operation of the device is suspended . The
pointer of the stopped movable part indicates a valu e
(e.g . 73.6 cm) that represents the snarliness value of
the examined yarn specimen. Th e high er the value,
the more snarly is the yarn.
Ten yarn specimens from each sample are
considered as the most appropriate for testing. The
atmospheric testin g conditions must be 65 ± 2 % RH
at 20 ± 2 DC under which the yarn samples must be
kept for cond itioning for 24 h.
2.1.3 Advantages of the Apparatus and the Method
The PRIANIC apparatus has the ad vantage of the
standard operation speed. The movable jaw moves
towards the stationary jaw at a constant speed of 0.5
cmls, giving the total maximum time of 200 s for
testing a dead yarn. In the existing vario us apparatus
and methods , there is no reference about the speed of
the movable jaw. Moreover, th e testing time using the
PRIANIC apparatus has been reduced remarkab ly in
rel ation to the time of the other methods that ranged
approximately between 10 min and 15 min .
Furthermore, the apparatus is supp li ed with a proper
yarn pretension system (tex/2 ±1O% g) that is strongly
recommended for testing yarn characteristics under
dynamic conditions. The most important feature of
the PRIANIC device and the accompanied method is
that the yarn forms freely a snarl in the most lik ely
part of it, confirming its unbiased testing principle.
The snarliness value given by the measurement of the
distance between the two yarn ends at the starting
point of the snarl formation makes this method
unrivalled.
2.2 Yarn Unwinding
The simple experiment shown in Fig. 5 was carri ed
out to investigate the effect of the yarn unwindin g
manner on yarn twist and twist liveliness. Two
parallel roving stripes were manually wound on a cop.
The over-end un wi nding added some twist in thi s
assembly. The added number of turns per unit length
of the unwound assembly with Z direction was equal
to the figured spira ls of that length on the cop (Fig.
Sa). On the contrary, the under-end unwinding (Fig.
5c) showed exactly the same behaviour apart from
that the twist direction was opposite, i.e. S direction.
When the assemb ly was unwound sideways, no
IND IAN J. FIBRE TEXT. RES ., MARCH 2003
26
a lterat ion in its stru ct ure was observed (Fig. 5b).
The over-end unwinding of the yarns from their
cop package adds most of the times some twist and
probably increases sli g htly the twist li ve liness of th e
yarns. It was shown that this twi st increase was
negligible when referred to yarn from cone packages
and therefore did not affect the twist li ve liness 7 . Thus,
it was decided fo r the various experiments to adopt
the conveni e nt, genera lly accepted and widely used
over-e nd yarn unwinding.
2.3 Prepara tion of Yarn Samples a nd Testing of Snarliness
2.3.1 Long-Staple Yarns
Yarn samples of 32 tex were produced from 100%
acry lic lo ng-stap le fibres with four different twist
fac tors. Meas uremen ts of th e yarn sna rliness of these
samp les were made o n th e PRIANIC appara tu s, with
set pretension of 15 g, every two days for a period of
20 days . The obtained results are shown in Fig. 6,
whi ch c learly shows the sig ni ficant role of the storage
time o n the re laxation of the twi st liveliness .
2.3.2 Short-Staple Yarns
Experiments were carried o ut to examine any
alterations of the snarliness level of short-stap le yarns
due to the poss ibl e effect of the following four
factors:
(i) the shape of the yarn package (cop, cone);
(i i) the twist factor of the yarn samp les;
(iii ) the time elapsed from the yarn production up
to the snarliness testing; and
(iv) the atmospheric conditions in wh ich the yarn
sampl es were sto red.
Cotton sing les ring-sp un Z-twisted yarns of
nominal linear densities 29 tex and 39 tex were
prod uced and wou nd o nto cops and cones. For both
these yarn lin ear densities, three nominal twist factors
(32, 34 and 39 turns.cm, l.tex V,) were chosen.
Quantities of these six yarn samp les were made up
Table 1-
into two lots. One of these lots was kept in a sta nd ard
testing laboratory e nvironment of 20±2 °C and 65 %
RH and was referred to as conditioned lot. The other
lot was kept in e nvironmen t of non -standard
co nditi o ns and was referred to as unco nditioned.
After the yarn sa mpl es production, their lin ear
densities and twist leve ls were tested and the means
are presented in Table 1. The effect of the yarn
package form of the unconditi oned lot, the first day
after the yarn production, on the yarn snarliness is
prese nted in Fig. 7. Table 2 shows the readings of
yarn snarli ness, taken from all th e yarn samples of
bo th lots after o ne and o ne hun dred days elapsed from
the yarn production day.
3 Results and Discussion
Fro m Fig. 6 it is obvious that the increased twi st
level of the lon g-staple yarn sa mpl es of both linear
densities resulted in an in crease of th e ir snarliness . On
the other hand, a ll the four yarn sam ples showed the
d ramati c decrease of the snarlin ess tende ncy on th e
very first two days after the ir production. Thi s
98
·1
112
Twi st factor, turns .cm .tex
/-+-
96
24 .0
- . - 29.3
- - - 27.5 .
--+- 30.8
1
E
u,94
(/)
(/)
Q)
c
'E 92
co
c
(f)
~
>-
90
88
86+------ -- ,--------,--------,- -------,
10
15
o
5
20
Time , days
Fig.6- Effect of yarn storage on snarl iness value
Effec t of yarn package on short-staple yarn tw ist
Yarn
sample
Linear density
tex
A
Twi st, turns.n'-'
B
C
Ac tu al twist factor
turns.cm·'.tex in
S,
29.3
603.9
592.7
598 .3
32.4
S2
29.3
656.5
63 1.2
643.9
34.9
S3
29.4
7 11.2
7 11.5
711.3
38.6
S4
39.4
522 .3
505 .5
5 13.9
32.3
S5
38.9
545.6
526 .8
536.2
33.4
S6
39.5
632.0
625 .6
628.8
39.5
A-Yarn on a cop package; B-Yarn on a cone package; and C-Average va lue of cop and
cone yarn twi st read ings
PR IMENTAS: DIRECT DETERMINATION OF YARN SNARLINESS
27
Table 2- Effect or yarn package, condi ti o ning and conditioning time on short-staple yarn snarlincss
Yarn
sample
Linear density
tex
S,
Twist factor
turns. cm · 1.tex Yl
29.3
32.4
S2
29.3
S)
29.4
38.6
39.4
32.3
S4
34.9
Ss
38.9
33.4
S6
39.5
39.5
Yarn
package
Yarn snarliness ,cm
C
D
I"
100"
I"
100 "
A
78.2
72.3
67 .0
52.6
B
43.8
41.9
43 .7
4 1.6
A
74.0
70.7
78 .3
73.0
B
55.7
49.3
59.9
52. 1
A
88. 1
86.8
89.9
80.4
B
67.0
64.4
61.9
59.5
A
76.1
75.0
78.6
69. 1
B
39.4
37 .7
56.4
37.3
A
79.9
74.9
73 .5
67 .6
B
58.8
49.3
45.1
4 1.2
A
89.6
88. 1
90.5
82.4
B
77.2
76. 1
65.1
52.5
A-Y3rn on a cop package; 13-Yarn on a co ne package; C-U nconditioncd yarn; and
D--Conditioncd yarn.
a Number of days intcrvcned between yarn production and testing.
100
90
oCone
~
Yam 39 lex
Yam 29 In
80
5
"'"'
"c
~c
III
.
E
>-
70
60
50
40
30
20
10
32.4
34.0
38.6
32.3
33.4
39.5
Twist Factor . tums .cm·' .texY.
Fig.7- Erfect of the yarn packagc form on yarn snarli ness
reduction in snarliness became smoother as the time
from the production day was steadily elapsed. It could
be also stated that yarn snarliness followed an almost
linear trend.
The data in Tables 1 and 2 aBd Fig. 7 show that although the differences in twist amount were very
small between cops and cones of the same yarn samples, the yarns from the cones in all the cases exhibited a relatively high reduction (20-40%) in snarliness. This was probably due to the tension applied to
the yarn resulting from the winding speed and tensioning devices on the winding machine. This tension
seemed to extend slightly the yarn, resulting in a rearrangement of the structure of the yarn cross-section.
Moreover, the same tension may be responsible for
the significant reduction in torque produced by the
twist insertion during the spinning process.
With an intervened time of 100 days from the
production day , the yarns from conditioned cones
showed, in most of the cases, smaller tendency to
form snarls. Th is may be due to the combination of
various factors such as the more efficient conditioning
of the yarn during the wi nding stage where the most
important factor was likely to be the wind , and th e
application of longitudinal tensile stress on the yarn.
Furthermore, a cross-wou nd cone had a much more
open structure. The better conditioning of the yarn in
the co ne form might also be due to lower tension
exist ing in the yarn for min g coils around the yarn
package, resultin g in a softer package when compared
with the cop form of the yarn package. Furthermore,
o n comparing the readin gs obtained by measuring the
yarn snarl iness after a period of 100 days with those
obtained one day after the yarn production, it can be
seen that the time factor contributed slightl y to the
snarli ness reduction of unconditioned yarns. On the
other hand, following the appropriate stat ist ical
analysis that was based on the fac torial des ign
analysi s of variance of these data, it could be stated
that, in some cases, apart th e great significan ce of the
factor yarn package form, the fac tors co nditionin g and
time were of noticeable importance for yarn
relaxation with a significance level above 95 %.
4 Conclusions
Twist li veliness remall1s a great problem,
manifesting itself as snarls in the yarns and spirality in
28
INDIAN J. FIBRE TEXT. RES ., MARCH 2003
knitted fabrics. The relative effectiveness of the
various apparatus used for determining yarn
snarliness and their disadvantages, concerning the
adoption of the biased testing, led to the development
of the snarling testing apparatus PRIANIC in an
attempt to overcome most of the limitations of the
earlier instruments. The validity of this instrument as
well the adopted simple testing method was shown
after testing a numerous series of yarns at different
twist factors. Because this apparatus is still in the
embryonic stage of development, many improvements
need to be made. These could be: (i) an electronically
adjusted pretension system that will be helpful mainly
during the yarn stretching test. This test is considered
as a sequential part of the snarl test. Except the
presence of the advanced pretension system, the
reverse movement of the movable bracket at various
speeds is considered as essential; and (ii) the use of a
counter with a rotating grip fixed on the movable
bracket offers the opportunity for yarn twist testing.
The twist alteration of the examined yarn will give the
capability for examining the character of the new yarn
status during the snarling test.
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