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Indian Journal of Fibre & Textile Research Vol. 17, December
1992, pp. 219-223
Response of polyester-viscose blends to air-jet spinning
ReD Kaushik. K R Salhotraa & G K Tyagi
The Technological Institute of Textile & Sciences. Bhiwani
125 021 . India
Received 31 March 1992
Unlike ring yarns, air-jet yarns owe their surface cohesion to
wrappers and their formation could be related not only to the
turbulence in the two nozzles but also to the combined influence of
the fibre properties and other process parameters. This paper
reports the contribution of polyester fibre denier, spinning speed
and second nozzle pressure to the characteristics of
polyester-viscose yarns spun on Murata-jet spinner. It is observed
that MJS yarns are slightly weaker, more even, have fewer
imperfections and higher extension, flexural rigidity and elastic
recovery. An increase in second nozzle pressure and spinning speed
causes an increase in the yam tenacity and flexural rigidity but
has an ad-verse effect on yam evenness. Breaking extension, on the
other hand, decreases with increase in second nozzle pressure and
decrease in spinning speed.
Keywords: Air-jet spinning. Murata-jet spinner,
Polyester-viscose yarn, Yam properties
1 Introduction With the advent of air-Jet spinning the ring
spinning system faced another strong competitor, in addition to
the rotor spinning system, from both economic and quality point of
view particu-larly in medium and fine count range. The experi-ence
gained so far has confirmed that polyester, acrylic and blended
yams can be successfully pro-cessed on this system. However, the
yarns pro-duced are reported to have different structural
characteristics. An elaborate study on the maxi-mum potential of
air-jet spinning technology would help engineer yarns for specific
textile sub-strates. Some researchers have studied the effects of
draft, nozzle pressure, take-up ratio and yarn linear speed on the
characteristics of air-jet yarns 1.2. However, not much work has
been re-ported on the combined influence of the fibre parameters
and process variables. This paper aims at exploring this area in
relation to the cha-racteristics of air-jet yarns.
2 Materials and Methods 2.1 Preparation of Yam Samples
Two sets of yarns of 12.3 tex were spun from two different
blends of polyester and viscose ray-on fi.breson ring and air-jet
spinning machines. The specifications of polyester and viscose
fibres
"Department of Textile Technology, Indian Inst itute of
Technology. New Delhi 110016. India
used are given in Table 1. The polyester fibres used in all the
yarns were high tenacity type and had essentially the same
characteristics except fi-bre linear density. For blending
polyester and vis-cose fibres, a predetermined quantity of each of
the two components was hand opened and a sandwiched blend was
obtained. The multilayered fibre material was carded twice on a MMC
card. The card slivers were drawn on a Laxmi Reiter draw frame
DonS. Three passages of drawing were given for all the blends, the
linear density of finisher sliver being adjusted to 3.0 ktex. The
sliv-ers were spun into yarns on. Murata air-jet spin-ner 802 MJS.
The material and process parame-ters used to produce these yarn
samples are given in Table 2. For ring spinning, the finished drawn
sliver was converted into a suitable rove using an OKK roving fram
e. Equivalent yarns were spun on Laxmi Reiter ring frame G 5/ 1
using the fol-lowing process parameters: Spindle speed, 13500 rpm;
Total draft, 32; and Twist multiplier, 3.0.
Table I - Specifications of polyester and viscose rayon
fibres
Fibre Fibre Fibre Tenacity Breaking
length denier glden extension
mrn 0/0
Polyester 51 1.0 5.18 24.1
Polyester 51 1.4 5.25 24.8
Viscose 51 1.4 2.01 18.5
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220 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992
2.2 Tests
All the yarns were tested for single strand strength and
hreaking extension on an Instron, 500 mm long test specimens being
elongated at 200 mm/ min extension rate. Mean breaking strength and
extension were averaged from 50 observations for each yarn sample.
Yarn uneven-ness and imperfections were recorded by the Us-ter
evenness tester. The flexural rigidity and elas-tic recovery of
yarns were tested on weighing ring yarn stiffness tester by ring
loop method 3.
3 Results and Discussion 3.1 Breaking S trength
Table 3 shows that the MJS yarns are about 14- 18% weaker than
the ring-spun yarns depend-II1g upon the fibre linear density, yarn
eomposi-
Table 2 - Spinning parameters for M1S yarns
Yarn Yarn Polyester Spinning NPI NP2
ref. compo- fibre speed kglcml kglcml
No. sition denier mlmin (P:V )
S I 80:20 1.0 200 3.0 3.5/ 4/ 4.5
S2 80:20 1.4 200 3.0 3.5/ 4/ 4.5
S3 65:35 1.0 200 3.0 3.5/ 4/ 4.5
S4 65 :35 1.0 190 3.0 3.5/ 4/ 4.5
S5 65:35 1.0 180 3.0 3.5/ 4/ 4.5
S6 65:35 1.4 200 3.0 3.5/ 4/ 4.55
S7 65:35 1.4 190 3.0 3.5/ 4/ 4.55
S8 65:35 1.4 180 3.0 3.5/ 4/ 4.5
NPI - First nozzle pressure; NP2 - Second nozzle pressure; P --
Polyester: and V - Viscose
tion, spinning speed and second nozzle pressure, The lower st
rength of MJS yarn can Le attriblJ.ed to its unique structure. For
both MJS and ring yarns, the tenacity increases with increase in
poly-ester fibre content owing to the higher tenacity and extension
at break of this fibre. In MJS yarns, the tenacity increases with
increasing spinning speed due to the longer wrapped-in length. Such
a trend is expected due to the fact that the in-creased air flow at
high speed causes the edge fihres to move away from the fibrous
strand and assists these fibres to become long wrappings. Apart
from fibre composition and production speed , the second nozzle
pressure seems to make a significant contrihution to the tenacity
of MJS yarns. Some earlier studies have shown that the yarn tensile
strength decreases with increase in second nozzle pressure~.
Contrary to this observa-tion, the present study shows that within
the sec-ond nozzle pressure range of 3.5-4.5 kg/cm2 the tenacity
increases with increase in pressure. This can only be attributed to
increase in transverse forces . Since there is no effective
migration of the core fibres , the transverse forces necessary for
the inter-fibre cohesion required to sustain external loading are
provided by the wrapper fibres wound on the surface of the core
fibres. These transverse forces would depend on the number of
wrap-pings, mean length per wrapping and wrapped-in length. As
expected, increase in fibre fineness re-sults in a. higher tenacity
for both ring and MJS yarns.
3.2 Breaking Extension
The values of breaking extension for ring and MJS yarns (Table
3) show that, in general, the
Table 3 - Effect of fibre denier. spinning speed and second
nozzle pressure on tenacity, breaking extension and unevenness of
polyester-viscose ring and M1S yarns"
Yarn Tenacity. g/tex Breaking extension, % Unevenness. U% ref.
No. Ring yarn M1S yarn Ring yarn M1S yarn Ring yarn MJS yarn
3.5h 4,Oh 4.5h 3.5h 4.0h 4.5 h 3.5 h 4N 4.5h
S I 25 .7 2 1.5 23.1 23.6 10.9 11.8 11.2 11.1 13.4 11.4 11.5
11.8
S2 24.5 20.7 22.1 22.6 10.6 11 .4 11.0 10.8 13.7 I I.7 1I.9
12.2
S:l D.X iY.5 20. Y 21.3 10.3 11.4 10.9 10.7 13.6 12 .1 12.4
12.6
S4 n.R 19.3 20.5 20.8 10.3 II.I 10.8 10.6 13.6 11.6 11.8 12.
1
S5 nR IR.R 20.0 2(U 10.3 10 .Y 10.7 10.4 13.6 II A 11.5 II.R
S6 22.9 IX .7 20.1 20.3 10.1 II.I 10.8 10.5 14.0 12.3 12.6 12
.R
S7 n.Y IX . ." It)A IY.7 I n. I IO.R 10.7 10.4 14.0 II.R 12.0
12.2
SX 22.Y 18.3 IY.2 19.5 10.1 10.7 10.5 10.3 14.0 11.7 11.
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KAUSHIK et al.: RESPONSE OF POLYESTER-VISCOSE BLENDS TO AIR-JET
SPINNING 221
MJS yarns are more extensible than their ring counterparts. The
breaking extension of ring and MJS yarns tends to drop as the
polyester fibre linear density is increased. The breaking extension
considerably decreases with increase in second nozzle pressure due
to greater compactness owing to increased transverse forces. This
is born out by the fact that the yarn diameter which can be taken
as an indication of compactness, decreases with increasing second
nozzle pressure irrespective of fibre linear density and yarn
composition. For 80:20 polyester-viscose yarn spun from polyester
fibres of 1.0 denier using the nozzle pressure of 3.5, 4.0 and 4.5
kglcm2 the yarn diameters were found to be 0. 145, 0.141 and 0.137
mm respect-ively. Increase in spinning speed results in a high-er
breaking extension for MJS yarns. Since the tensile behaviour of
MJS yaros critically depends on the wrappers for inter-fibre
cohesion, their formation is a combined effect governed , to a
large extent, by the fibre parameters, stiffness of the fib re-mix
and process variables. With regard to the contribution of process
parameters to breaking load and extension at break of polyester MJS
yarns, Chasmawala el aU reported a close association between yarn
structural parameters and tensile characteristics.
3.3 Yarn Unevenness
Table 3 shows that the MJS yarns are more even and have less
imperfections than the corre-
sponding ring yarns. The lower unevenness of MJS yarn can be
attributed to the higher drafting speeds wherein the inertia effect
allows fibres to be pulled out without much disturbance in the
ad-joining fibres. The formation of high amplitude drafting waves
is thus clearly avoided as less num-ber of fibres can move out of
turn. The polyester fibre content hardly affects the unevenness of
MJS yarns. The U% values tend to increase with an increase in both
polyester fibre linear density and second nozzle pressure. In
spinning yarns from coarse fibres , less fibres are presented at
the front roller nip so that the fibres are individual-ized, which,
in turn, increase the production of edge fibres . In addition to
this, the number of fi-bres in strand cross-section considerably
dec-reases with increase in polyester fibre denier. This partly
explains thc slightly more unevenness ob-served for MJS yarns spun
from coarse polyester fibres at high second nozzle pressure. Apart
from the fibre denier and nozzle pressure, the produc-tion speed
also appears to contribute to yarn un-evenness. For all the yarns,
U% increases as the production speed is increased. The increase in
unevenness of MJS yarns can be attributed to the greater
disturbance due to increased air-flow at front roller nip at
increasing production speed I .
3.4 Imperfections The imperfection values for ring and MJS
yarns
(Table 4) show that for both these yarns, the thick
Tahle 4 - Effect of fibre denier. spinning speed and second
nozzle pressure on imperfections of polyes ter-viscose ring and MJS
ya rns"
Yarn Imperfections/ 125 m
ref. No. Ring ya rn MJ 5 yarn
Thin T hick Neps 3.5" 4.0" 4.5"
places places + 200 - 50'X. + 5()o;,. Thin Thick Neps Total T
hin Thick Neps Total Thin T hick Neps Total
places places + 200 places places + 200 places places + 200 -
51l% + 50'V. . - 51l% + 50% - 500;.. +50%
5 1 14 42 7X :1 II "27 -1 1 3 III 24 37 4 I.) 25 :1X
S2 16 olX T\ :' 17 "2:1 ol:; ol 12 22 3X 7 II 20l .Q
S3 17 52 6X 6 15 20l ol5 7 17 II.) 43 10 Iii 22 411
54 17 5~ (IN i-\ 13 ..,.., ol3 In 16 II.) ol5 12 1(, 2 1 ol9
S5 17 :;2 lii-\ II X 2 1 olll 12 I] 17 42 14 12 IX 44
S(, 2() 5X (, I l) ILJ 2 1 oll.) I.) 19 17 ol 5 12 2 1 19 52
S7 20 :;X ii i LJ 16 ILJ 44 10 15 15 40 13 20 15 4X
SX 2() 5X (li 1"2 15 17 olol II 15 lol olO 16 IX 15 oll)
., Ya rn linear density. 12.3 tt! X; and I· St!cllnd nozz it:
prt!ssurt! in kg/cm:
.. --- .'._----_ ... _-
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222 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992
Table 5 - Effect of fibre denier, spinning speed and second
nozzle pres!;ure on flexural rigidity and elastic recovery of
polyester-viscose ring and MJS yams"
Yarn Flexural rigidity x IOJ , g.cm~ Elastic recovery, % ref.
No. Ring MJSyarn Ring MJS yarn
yarn yam 3.5h 4.0h 4.5h 3.5h 4.0h 4.5h
SI 1l.1l 11.2 12.8 13.1 63.6 59.9 51l.1l 57./l
S2 8.6 10.8 11.9 13.3 62.4 56.8 56.6 55.8
S3 R.2 10.4 II.S 12.R 5R .R 54.3 53.9 53.7
S4 R.26 9.7 10.8 12.3 58B 53.1 52.4 52.1
S5 8.2 R.74 10.2 11.2 5R .R 51.R 51.2 50.1
S6 7.R 9.4 11.6 12.4 56.6 51.R 50.1 49.1
S7 7.X 9. 2 10.2 II.X 56.6 50.3 49.6 48.9
SR 7./l 9.1 9.4 10.7 56.6 49.1 4R.9 47 .2
"Yarn linear density, 12. 3 lex; and "Seconu nozzle pressure in
kg/cm '
and thin places slightly increase with the increase in fibre
denier, as expected. Incidentally, the sec-ond nozzle pressure does
not affect imperfections, the latter, however, alter with spinn\ng
speed. As is evident from the test results, the thick places and
neps are less in yarns spun at low spinning speed and increase as
the spinning speed is in-creased. Thin places, on the other hand,
appear to decrease with increasing spinning speed. The total
imperfections show very slight difference at different spinning
speeds and fibre deniers.
3.5 Flexural Rigidity
Table 5 shows that the MJS yarns are stiffer than the ring-spun
yarns, irrespective of fibre line-ar density and yarn composition.
In MJS yarns, the fibres in the core lie parallel to the yarn axis
and the sheath fibres wrap around them. The par-allel fibre core
tends to act as a group as the wrappers considerably restrict the
freedom of their movement during bending. Hence, the flexu-ral
rigidity indices for MJS yarns are considerably higher than those
for the equivalent ring yarns.
For both ring and air-jet yarns, the flexural ri-gidity
increases with decrease in polyester fibre denier; the flexural
rigidity being inversely pro-portional to the bending rigidity and
is in line with the accepted fact that fine denier fibres have
lower bending rigidity5.6 . Furthermore, an increase in the
polyester fibre content results in an in-crease in flexural
rigidity due to the higher modu-lus of polyester fibres . Table 5
also shows that the flexural rigidity of MJS yarns increases with
in-crease in both spinning speed and the second
nozzle pressure. This can be accounted for by the role played by
the wrapper fibres. In MJS yarns, the degree of the freedom of
fibre movement, which is largely determined by the inter-fibre
fric-tion, is impaired by the transverse forces. At high-er
spinning speed and higher second nozzle pres-sure, the number of
wrapper fibres and the wrapped-in length increase, causing a lower
de-gree of freedom of fibre movement and hence a higher flexural
rigidity.
3.6 Elastic Recovery
Table 5 shows that the ring yarns have higher elastic recovery
than the MJS yarns owing to the longer length of the fibre
available per unit length in the former. Like in ring yarns, the
elastic re-covery of MJS yarns is higher for yarns having higher
polyester fibre content and it shows no significant change with
increase in the second nozzle pressure. Surprisingly, the variation
in spinning speed hardly affects the elastic recovery of MJS yarns,
although yarns spun at higher pro-duction speed exhibit slightly
higher elastic re-covery. The apparent behaviour can be ascribed to
the variability of strains associated with the presence of wrapper
fibres 5.
4 Conclusions 4.1 MJS yarns are slightly weaker but more
exten-sible as compared to their ring counterparts. The tenacity of
all the yarns increases with increase in fibre fineness, polyester
fibre content, spinning speed and second nozzle pressure. However,
the breaking extension decreases with an increase in
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KAUSHIK ef lIf.: RESPONSE OF POLYESTER-VISCOSE BLENDS TO AIR-lET
SPINNING 223
the second nozzle pressure and decrease in spinn-ing speed. 4.2
MJS yams, at all spinning speeds, are more even than the ring yams.
However, yam evenness deteriorates with increasing polyester fibre
denier, second nozzle pressure and spinning speed. 4.3 MJS yams
have fewer imperfections than the ring-spun yams and show no
significant change with increase in second nozzle pressure.
However, an increase in spinning speed results in an in-crease in
thick places and neps but decrease in thin places. 4.4 MJS yams
have considerably higher flexural rigidity and elastic recov~ry,
which further in-
creases with increase in polyester fibre fineness . An increase
in second nozzle pressure and spinn-ing speed increases the
flexural rigidity but has no significant effect on elastic
recovery.
References I Grosberg P, Oxenham W & Miao M, 1 Texf Insf, 78
(1987 )
189,204. 2 Chasmawa1a R 1 , Hansen S M & layaraman S, Text
Res 1,
60 (1990 ) 61. 3 Owen 1 D & Riding G, 1 Text Inst, 55 (1964)
T414. 4 LawrenceCA& Baqui MA, Text Res 1, 61 (1991) 123. 5
Kaushik R C D, Sa1hotra K R & Tyagi G K, Indian 1 Text
Res, 12 (1987 ) 220. 6 Truerron W, l Text Inst, 76 (1985 )
454.
