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Dynamic Properties of Air-Jet Yarns Comparedto Rotor-Spun Yarns

ARTICLE in TEXTILE RESEARCH JOURNAL · FEBRUARY 2015Impact Factor: 1.33 · DOI: 10.1177/0040517514563726

3 AUTHORS , INCLUDING:

Mohamed Eldessouki

Technical University of Liberec

31 PUBLICATIONS 5 CITATIONS

SEE PROFILE

Ramsis Farag

Auburn University

14 PUBLICATIONS 4 CITATIONS

SEE PROFILE

Available from: Mohamed EldessoukiRetrieved on: 24 August 2015

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Original article

Dynamic properties of air-jet yarnscompared to rotor spinning

Mohamed Eldessouki 1,2 , Sayed Ibrahim 3 and Ramsis Farag 2,4

AbstractIn yarn production, the mechanism of twist insertion is a major factor that affects the structure and ultimately theproperties and characteristics of the produced yarn. Moreover, the differences within the same spinning technique mayhave a similar effect where, for instance, the properties of yarns produced using Murata Vortex Spinning (MVS) andReiter air-jet spinning (J20) will differ, although both technologies are just varieties of the same twist insertion principle of using a stream of air. In this work, the structure and properties of Murata vortex, Reiter, and rotor-spun yarns arecompared with more emphasis on their mechanical behavior under dynamic stresses. Unlike the dynamic mechanicalanalysis of materials that presumes linear viscoelastic behavior and is only valid under small strains, this work suggests acyclic loading with larger strains as a means of the dynamic evaluation of the yarns. Results show no significant differencebetween the technologies in terms of their initial modulus and maximum elongation, while a significant differencebetween the technologies is observed in the maximum loading and, to some extent, the work of rupture. The dynamicsonic modulus is compared to the results of the standard mechanical and the suggested cyclic loading tests, and a highcorrelation between the values was observed.

Keywordsair-jet yarns, dynamic modulus, Rieter jet-spinning, Murata vortex-spinning, viscoelastic properties of yarn

IntroductionThere is a direct relation between the yarn forming pro-cess, structure, properties, and performance. Yarnproduction technology identies the ‘‘yarn formingprocess’’ term in this series of relations, where ring-spinning, rotor spinning, air-jet spinning, friction spin-ning, etc., are found to have different effects on theproduced yarns. Each production technology has itsown advantages and disadvantages, as determinedwithin a certain application window. Air-jet spinning,

for instance, was found to be successful in producingyarns with reasonable tenacity (Figure 1(a)) at a rela-tively much higher speed than the ring spinning and therotor spinning (Figure 1(b)). 1 The Murata Jet Spinner,MJS 801, was rst exhibited at ATME-International in1982 as a modication of the fasciated spinning systemintroduced by Du Pont in 1956. 2 At that stage, thesystem had some constraints on producing yarns of 100% cotton or cotton-rich blends, which was thensolved by introducing the Murata Vortex Spinning(MVS) that allows processing these bers and produ-cing ne yarn counts.

In 2003, the Rieter Group introduced its own J10air-jet spinning technology that was updated in 2008with J20, which was commercialized with 200 spinningunits and up to 500 m/min delivery speed. The jets usedin Murata and Rieter are different in design and con-struction but produce jet yarns based on the same prin-ciple of twist insertion by the stream of air. In both

1 Department of Materials Engineering, Technical University of Liberec,Czech Republic2 Department of Textile Engineering, Mansoura University, Egypt3 Department of Textile Technology, Technical University of Liberec,Czech Republic4 Department of Polymer and Fiber Engineering, Auburn University, USA

Corresponding author:Mohamed Eldessouki, Department Materials Engineering, TechnicalUniversity of Liberec, Studentská 2 461 17 Liberec 1 Liberec, CzechRepublic.Email: [email protected]

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systems (MVS and Reiter), bers leave the front rollerof the drafting device and are drawn into the berstrand passage by air suction created at the nozzle.The distance between the nozzle tip and the draftingroller is crucial in generating the free ber ends andthis distance should be slightly shorter than the averagelength of the bers being processed, because bersshorter than this distance are usually lost and directedto the waste. 3 According to the air pressure, the vortexcan revolve at speeds of 1,000,000rpm, which allows atwist of bers with a rotation speed of 300,000 rpmwhere the speed difference is attributed to the mechan-ical friction. 3 The vortex stream focuses the leadingends of the bers at the yarn center and directs the

trailing ends to form the outer layer that wraps theyarn. This action results in a yarn structure withbers at the core with a very low twist and are almostparallel, while the twist level grows with increasing yarndiameter (yarn build up). Due to the vortex forces andthe twist of the surface bers, a certain torque is gen-erated in the yarn being formed. This torque has thetendency to twist the ber bundle between the draftingunit and spindle. This kind of twist must be avoided toprevent interference with the generation of the neces-sary free ber ends. Therefore, the two systems adoptedtwo solutions for this problem, where Murata used a

needle in the nozzle block, as illustrated in Figure 2(a),and Reiter used a curved path of the bers at the nozzletip with an arc shape, as shown in Figure 2(b). The berpath is another difference in the design of the nozzles of the two systems. In the Murata system, the draftingsystem is located above the spinning nozzle and yarnsare delivered at the bottom. For space efficiency rea-sons, Rieter reversed the setup and the sliver is fed fromthe bottom and delivered yarn is wound up at the topafter passing the air-jet twist insertion.

Air-jet yarns were compared with other spinning sys-tems in the literature, 5–8 where Soe et al. 4 produced

cotton yarns spun on the MVS system and comparedthem with yarns spun on ring and open-end rotor sys-tems. Their work focused on the structure of the yarnsand the differences in ber pitch, arrangement, andangles, as well as some yarn parameters such as theyarn diameter, helix angle, hairiness, evenness, and ten-acity. The study found MVS yarns to be the bulkiestamong the three yarns, with more parallel bers at thecore (with almost no twist) and wrapped by otherbers. MVS yarns were also found to be stiffer thanring and rotor-spun yarns, while the ring-spun yarnshowed the highest tenacity values. Another compara-tive study for the MVS system with ring and rotor-spunyarns was performed by Erdumlu et al., 6 where the

performance of these yarns from different materialsand different counts was compared after transformingto knitted nished fabrics. MVS yarns showed the leasthairiness and the highest pilling resistance among thethree systems. The dimensional stability and the burst-ing strength of the Vortex knitted fabrics were close tothose of the fabrics from ring spinning and outperformthe fabrics of rotor spinning. The VORTEX website byMurata-Machinery 7 demonstrates some structural andproperty differences between the Vortex, the ring, andthe rotor-spinning systems. Figure 3 shows the twistdistribution across the cross-sections of the three

yarns where twists are almost constant in ring-spunyarns. The gure also shows the possibility of wrappingbers to change their twist direction at the surface of rotor yarns, while a monotonic increase in twist inten-sity is observed in vortex yarns with more parallel bersat the yarn core.

In this work, we are trying to go beyond the com-parison of different systems to compare yarns of thesame family that are produced using the same produc-tion principle with more emphasis on physical proper-ties of the yarns under dynamic loading. This papertries to investigate the relatively new air-jet system

Figure 1. (a) Relationship between the tenacity and the yarn counts for ring-spun, Murata Vortex Spinning (MVS), and open-end(OE) yarns. (b) Comparative production speeds for different yarn counts produced on ring-spinning, MVS, and OE systems. 1

2 Textile Research Journal 0(00)




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developed by Rieter and compares its properties toother systems of the same family (e.g. MVS) as wellas other systems (e.g. rotor spinning). The studybegins with the structure of the yarns as observed

using Scanning Electron Microscopy (SEM) and pro-ceeds with physical properties of the studied yarns.Mechanical testing of the yarns was performed usingthe commonly used single-end strength tests at constantrate of extension (CRE) as well as cyclic loading/unloading. The sonic modulus of the yarns was inves-tigated using the Dynamic Modulus Tester (DMT).

Methods

Cyclic modulusTesting of yarn behavior under dynamic loading/unloading is required to simulate the actual loadingscenarios during the end use of the yarn. This kind of testing is necessary for certain applications, such as tirethreads and carpet pile yarns 9 (where yarn resiliencecan be measured before the production of the endproduct). Warp threads are also subjected to dynamic

loading during the weaving process.10

The dynamicloading of yarns is usually studied within the viscoelas-tic properties of the material, where a sinusoidal straine (sinusoidal stress is applied in some experiments) withcertain amplitude em is applied to the yarn in the form

e ¼ em sin ! tð Þ ð1Þ

where ! ¼ 2 :F is the angular frequency (radian/second), F is the frequency in Hertz, and t is the timeof application. At steady-state conditions, the devel-oped stress f in the ber’s material will also have a

Figure 3. Twist distribution through the cross-section of yarnsproduced on different spinning systems (color online only). 6

Figure 2. Illustrations for the Murata Vortex Spinning system (a) 3 and the Rieter jet spinning (b). 4

Eldessouki et al. 3




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sinusoidal shape and will be related in phase to theimposed extension as

f ¼ f m sin ! t þ ð Þ ð2Þ

where f m is the stress amplitude and d is the angular

phase difference between the applied extension and theresulting stress. According to this relation, and usingthe trigonometric identities, the stress can be rewrittenin the form

f ¼ f m cos ð Þ: sin ! tð Þ þ sin ð Þ: cos ! tð Þ½ ð3Þ

Therefore, the stress can be considered as two com-ponents: one that is in-phase with the strain and equals f m : cos ð Þ, and another that is 90 out-of-phase andequals f m : sin ð Þ. These values are used to dene thedynamic modulus of the material as

E ¼ in phase stress amplitude

strain amplitude ¼

f m : cos ð Þem

ð4Þ

Also, the dissipation or loss factor of the material ( w)can be calculated as

¼ out of phase stress amplitude

in phase stress amplitude

¼ f m sinð Þ f m cosð Þ

¼ sinð Þcos ð Þ

¼ tan ð Þð5Þ

These parameters are commonly used in evaluating

the dynamic behavior of textile materials, but it shouldbe noted that these parameters, according to the abovelisted equations, are only valid for materials that obeythe laws of linear viscoelasticity. Most textile bers,however, are known for their nonlinear behavior,which means that these parameters can only be appliedat very small strains, otherwise they might be con-sidered as approximates to the material behavior. 11

Therefore, this study suggests the cyclic loading in away that simulates the actual loading scenarios byapplying higher strains on the yarn. However, theapplied strain is limited to have loading cycles within

the region around the approximated yarn’s yield point,where the slope modulus of the load–elongation curvechanges signicantly. The maximum load during load-ing cycles was about 30–40% from the strength of theseyarns, then the yarn was unloaded without reaching astress value of zero to keep an initial or a static load onthe yarn at the beginning of each cycle. Some param-eters were extracted from each curve; among them thecyclic modulus and the resilience were examined duringthe study of these yarns.

The ‘‘ cyclic modulus ’’ can be expressed as the chordmodulus of the load–elongation curve at different

dynamic loading cycles. 9,12 The calculation of thismodulus is slightly modied from the chord modulusby considering the slope of a tted trend line (insteadof the chord line itself) for the loading portion of thecycle. The yarn’s delayed recovery was not consideredduring the unloading cycle and the calculation of the

tting line excludes the unloading portion of the cycle,because this portion mainly depends on the viscoelasticproperties of the bers, their relaxation time, and theunloading speed. Figure 4 shows a typical dynamic load-ing of a vortex yarn that goes under 40 loading cyclesand the inset of the gure shows an example for the rstcycle, where the loading and unloading portions wereidentied and the modulus of this cycle is calculated asthe slope of the demonstrated dotted trend line.

The ‘‘ resilience ’’ (R ) of the yarn at each cycle is cal-culated by the numerical integration of the yarn load(P ) as a function of its elongation ( x) to calculate thearea under the curve ( W ). This can be expressed math-ematically as

W ¼ Z xmax

xmin p xð Þdx ð6Þ

The resilience of the i th cycle ( R i ) represents the hys-teresis during that cycle and can be calculated as thedifference between the loading and the unloading por-tions of the cycle as follows:

R i ¼ W load i W unload i ð7Þ

Sonic modulusThe dynamic (sonic) modulus is based on a principle of the pulse propagation and its speed in the material. Tomeasure the sonic speed, an apparatus with two trans-ducers (transmitter and receiver) that touch the yarnspecimen and the time interval for the pulse to travelfrom one to the other is measured. By knowing the dis-tance between the transducers and the measured time,the sonic speed C through the material can be measured,and this speed can then be used in calculating the

sonic modulus of the yarn according to the relation

E ¼ :C 2 ð8Þ

where E is the sonic modulus in GPa, C is the sonicspeed in the material in km/s, and is the materialdensity in (g/cm 3). This relation can be reformulated to

E ¼ k:C 2 ð9Þ

where E is the sonic modulus in cN/denier, C is thesonic speed in the material in km/s, and k is a constant





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The initial modulus, the maximum load, the maximumelongation, and the work of rupture were extracted andanalyzed to differentiate between these curves. Identicalvalues for these four parameters with their statistics areshown in Table 1 for the different yarns. Studying theseresults shows that Rieter yarns have an elastic modulusslightly higher than that of rotor yarns, while Vortex

yarns have a lower modulus value. A trend similar tothat for the modulus can be observed for the maximumelongation property while the other yarn parameters,such as the maximum load and the work of rupture,have a slightly different trend where Rieter yarns havethe highest values followed by Vortex then rotor yarns.It is important to note that this ranking in properties

Figure 6. Force–extension relations for the Rieter, Murata Vortex Spinning, and rotor yarns: (a)–(c) individual curves.

Figure 5. Scanning electron microscope pictures for the longitudinal view of Rieter, Murata Vortex Spinning, and rotor yarns,respectively.





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does not give absolute superiority to a system over theother where the values of the yarn properties are usu-ally related to the required end product’s performance.The analyses of variance (ANOVAs) for these

parameters are indicated in Table 2, which shows nosignicant difference between the yarn production tech-nologies in terms of their initial modulus and maximumelongation while a signicant difference between thesetechnologies in terms of their maximum loading isobserved, which is also reected on the work of rupturewith some degree of signicance. The signicant differ-ence between the maximum load for each yarn can beattributed to the different arrangement of bers insidethe yarn, where more parallel bers were observed inthe Rieter production technology as demonstrated ear-lier in the SEM pictures.

The mechanical behavior of the yarns under cyclicloading is shown in Figure 7 for the different types of yarns. The calculated dynamic moduli as well as theresilience of the yarns at different loading cycles are

shown in Figures 8 and 9, respectively. It can be seenfrom Figure 8 that the yarn modulus increases with theincrease in the number of loading cycles. This behaviorcan be explained by increasing the alignment of bersto the yarn axis every time the load is applied on theyarn. This alignment increases the helical angle of thebers and allows more bers to resist the applied load,which consequently increases the measured modulus.Increasing the orientation of bers results in increasingtheir utilization factor in the yarn and allows stifferbehavior of the yarn at higher numbers of loadingcycles. The cyclic modulus increased after 40 cycles by

Table 2. Analysis of variance for the mechanical properties of the different yarns

Source of variation SS df MS F P-value F crit

Modulus Between groups 85.5115 2 42.7558 0.4491 0.6429 3.3541Within groups 2570.6440 27 95.2090Total 2656.1555 29

Maximum force Between groups 2.2482 2 1.1241 5.2392 0.0120 3.3541Within groups 5.7930 27 0.2146Total 8.0412 29

Maximum strain Between groups 3.2639 2 1.6320 0.2153 0.8077 3.3541

Within groups 204.6553 27 7.5798Total 207.9193 29

Work of rupture Between groups 172.2703 2 86.1351 2.1693 0.1338 3.3541Within groups 1072.0674 27 39.7062Total 1244.3377 29

Table 1. Mechanical properties of the different yarns

Sample number

Young’s modulus [g/denier] Maximum force [N] Maximum elongation [mm] Work of rupture [mJ]

Rieter Vortex Rotor Rieter Vortex Rotor Rieter Vortex Rotor Rieter Vortex Rotor

1 69.8 54.7 44.0 2.932 1.688 2.020 14.154 7.420 12.256 25.473 8.462 15.337

2 63.9 57.3 61.3 3.262 1.973 1.484 14.184 10.220 10.240 28.006 12.955 9.4813 64.7 55.3 70.8 2.853 2.613 1.342 11.557 14.507 6.801 21.214 24.020 5.8354 55.5 63.7 54.5 2.730 2.316 1.745 13.644 10.696 10.441 23.421 15.997 11.6335 53.5 57.6 60.7 2.645 1.635 2.075 12.529 7.492 12.430 20.467 8.120 17.0316 54.1 82.0 90.5 2.664 2.750 2.029 12.737 14.163 7.375 20.940 25.009 9.8397 74.0 66.5 66.1 3.214 2.276 2.070 15.206 10.239 13.575 29.689 14.874 17.9108 70.8 54.9 57.8 1.438 2.164 2.123 6.226 11.431 13.714 6.198 17.146 18.5839 70.8 64.0 69.0 1.438 2.658 2.057 6.226 11.706 14.816 6.198 19.846 18.98610 73.4 54.9 66.3 2.549 1.995 2.084 10.774 11.353 12.500 17.267 14.469 16.488Average 65.060 61.092 64.086 2.573 2.207 1.903 11.724 10.923 11.415 19.887 16.090 14.112Stand. dev. 8.050 8.547 12.156 0.642 0.391 0.280 3.177 2.344 2.674 8.100 5.709 4.573

Eldessouki et al. 7




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about 25.7%, 25.9%, and 29.4% from its value at therst cycle for Rieter, Vortex, and rotor yarns, respect-ively. Also, the rate of change in the cyclic moduluswith the number of cycles is almost the same for allyarns produced on different technologies, which mightbe attributed to the use of the same ber material in all

yarns. On the other hand, the relatively higher increasein the cyclic modulus of the rotor-spun yarn revealshigher rearrangement of the bers, which is expected,because those yarns are known to be bulkier and havehighly random orientation.

The resilience of the yarns is demonstrated by theirhysteresis, which was found to decrease after the appli-cation of the cyclic loading with a tendency of the load-ing and unloading curves to get closer until beingnearly identical after a certain number of cycles. Thecontinuous shift of the hysteresis loops is due to thecreep properties of the material and a permanent

deformation was found to form in the material aftercertain number of cycles. The rate of change in yarnresilience (the slope of the curves in Figure 9) is similarin all yarns, which can be attributed to the characteris-tics of the viscose bers used in all these yarns.

The calculation of the sonic modulus is based on the

sonic speed in the yarn material, as indicated earlier.Sonic speed is the relation of the distance between send-ing and receiving probes to the traveling time of thesonic pulses, as shown in Figure 10 for individualyarn samples. The dynamic sonic moduli, as calculatedfrom sonic speeds in the yarns material, are listed inTable 3 with their ANOVAs shown in Table 4. It canbe noticed that the dynamic moduli calculated from thesonic test are correlated to the Young’s moduliobtained from the standard test (as shown inFigure 11) and, therefore, the sonic tester can be pre-ferred as a non-destructive way of measuring the

Figure 7. Load–elongation behavior of the Rieter, Murata Vortex Spinning, and rotor yarns under cyclic loading.





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Young’s modulus of the material. The sonic tester isalso more sensitive to many of the material parameters,especially at the microscopic and molecular levels.Sonic modulus, for instance, is sensitive to the bercrystallinity, the ber orientation, and the packingdensity of bers inside the yarn (where the effect of porosity and pulse transfer across different media isconsidered). According to these sensitivity issues, themodulus measured with the sonic test might be lower

than that measured with the standard test, as shown inFigure 11. Further investigations might be required totake one or more of these parameters in account toincrease the precision of the sonic testing method.

ConclusionStaple ber yarns were produced on different systems of twist insertion mechanisms. All yarns were made of

Figure 8. Change in yarn modulus after many cycles of loading.

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 5 10 15 20 25 30 35 40 45

Y a r n

R e s

i l i e n c e

[ N . m

m ]

No. of loading cycle

Rieter

Vortex

Rotor

Figure 9. Change in yarn resilience after many cycles of loading (color online only).

Eldessouki et al. 9




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viscose bers. Results show that the tested yarns haveno signicant difference in terms of their initial modu-lus and maximum elongation, while a signicant differ-ence between the technologies is observed in themaximum loading and, to some extent, the work of rupture. The cyclic modulus of all yarns increasedwith the same rate by increasing the number of loadingcycles due to the better orientation of the bers insidethe yarns, while a slightly higher increase in cyclic

modulus was observed with rotor yarns as their initialber orientation is more randomized. The dynamicmodulus, calculated through the sonic speed in theyarn material, was found to be highly correlated tothe Young’s modulus, calculated from the regularyarn breaking test, which gives an indication as to thevalidity of using such a non-destructive test for evalu-ating the yarn materials. This work will extend to inves-tigate the physical properties of air-jet yarns with the

8

10

12

14

16

18

20

22

60 70 80 90 100 110 120 130

D i s t a n c e

[ c m

]

Time [microseconds]

Reiter 1

Reiter 2

Reiter 3

Reiter 4

Reiter 5

Rotor 2

Rotor 3

Rotor 4

Rotor 5

Rotor 1

Vortex 2

Vortex 3

Vortex 4

Vortex 5

Vortex 1

Figure 10. Plot of the individual readings of sonic pulse times at different probe distances used to calculate the sonic speed (coloronline only).

Table 3. Sonic (dynamic) modulus [g/denier]

Reiter Vortex Rotor

62.09 49.88 66.5455.63 52.01 49.1268.56 46.05 62.8052.75 46.69 53.7155.18 53.60 45.89

Average 58.84 49.65 55.61Stand. dev. 6.44 3.28 8.82

Table 4. Analysis of variance for the sonic modulus

Source of variation SS df MS F P-value F crit

Between groups 217.762 2 108.881 2.511974 0.122666 3.885294Within groups 520.137 12 43.345Total 737.899 14





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interaction between machine parameters (e.g. nozzlediameter, air pressure, delivery speed, etc.) and internalyarn structure (e.g. core-to-sheath ratio, amount of twist inserted, etc.) for different ber materials andyarn counts.

Funding

This work was supported by the ESF operational program‘‘Education for Competitiveness’’ in the Czech Republic inthe framework of project ‘‘Support of engineering of excellentresearch and development teams at the Technical Universityof Liberec’’ No. CZ.1.07/2.3.00/30.0065.

References1. Cotton Incorporated. Air jet spinning of cotton yarns.

Technical Bulletin, TRI 1001, 2004.2. Basu DA. Progress in air-jet spinning. Text Prog 1999; 29:

1–38.3. Rieter. RIKIPEDIA- The Rieter Textile Knowledge Base,

http://www.rieter.com/en/rikipedia/navelements/main-page/ (accessed 25 August 2014)

4. Rieter. J 20 air-jet spinning machine, Increased productiv-ity and new winding system for perfect Com4 Jet thread.Family Event Turkey, 2014.

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14. ASTM D2256 - 02. Standard test method for tensile prop-erties of yarns by the single strand method, 2002.

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Figure 11. Average moduli of different yarns as measured using the sonic tester and the standard tension test.

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Documents

2015_Dynamic Properties of Air-Jet Yarns Compared to Rotor-Spun Yarns_2.pdf