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Indian Journal of Fibre & Textile Resea rchVol. 16, Marc h 199 1, pp. 29-38

Air-jet texturing: Effect of jet type and some process parameters onproperties of air-jet textured yarnsV K Kothari & N B Timble

Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, IndiaReceived I December 1990

The distinguishing features of different air texturing jets have been described and the test methods used toassess some impo rtant properties of air textured ya rns have been discussed. The properties of air texturedyarns produced using various currently used commercial jets have been compared. The results show that theperformance ofcylindrical jet s and Taslan type XX je t for para llel end tex turing of 76 den J36 fil polyesteryarns is superior. The effects of some important process parameters such as overfeed percentage, air pressureand heater temperature on various proper ties of air-jet textured yarns have bee n reported . The relationshipsbetween air-jet textured ya rn propert ies and processing parameters have been assessed in terms of regressionequations and it has been shown that with a few exceptions, most of the properties of air-jet textured yarns arelinearly related to the process parameters studied .Keywords: Air-jet texturing, Instability, Loops, Phys ical bulk, Texturing jet

1 IntroductionIn the air-jet texturing process, an overfed bundleof filaments is subjected to the action of a turbulent airstream. The air stream separates the individualfilaments of the overfed yarn and transforms theexcess length of each filament into a series ofloops andarcs at randomly spaced longitudinal intervalsseparated by relatively straight portions. Air-jettexturing is ba sically a mechanical process and can beused for both thermoplastic and non-thermoplasticfilament yarns as well as for their blends. The texturedyarns produced by this process resemble the naturalfibre based spun yarns both in appearance andphysical characteristics . The increasing consumerdemand for the spun yarn look and natural fibre feel ,and the increasing use of synthetic and otherman-made fi lament yarns have made the air -jettexturing process extremely important for the textileindustry and its share is expected to show a steadyincrease . The following factors have contributed toits growing popularity : (i) the unique capabilities ofthis process; (ii) the desirable characteristics of theresultant yams; (iii) the availability ofa wider range ofsuitable supply yarns; and (iv) the deve(opments injetdesign which have resulted in reduced ai rconsumption and improved process economics.The developments in air texturing jets and thedistinguishing features of different je ts are firstdescribed in this paper. This is followed by adi scussion of the important properties of the air-jet

textured yarns and the test methods adopted formeasuring these properties. The properties of air-jettextured yarns produced using different jets are thencompared. Finally, the effects ofimportaht processparameters such as overfeed percentage, ai r pressureand heater temperature on the properties of air-jettextured yarns have been studied and analyzed .2 Air Texturing Jets

Industrially used ai r texturing jets, also referred toas nozzles, can be categorized (depending upon theirinternal design and construction) into two maingroups: (i) converging and diverging type airtexturing jets in which a converging-diverging flowduct (nozzle) is attached to the ya m exit end of the je tassembly; and (ii) cylindrical jets in which one or moreair inlet hole(s) open at an angle to the cylindrical flowduct (nozzle) inserted in a suitable je t housing. Theya rn exit end of these cylindrical nozzles is oftentrumpet shaped. Figs l(a) to (f) show various jets ofthe converging-diverging type while Fig. 2 shows thecore of a cylindrical nozzle.Basically, Taslan type IXjet(Fig. la ) consistsofaventuri into which an adjustable hollow needle isinserted at an angle of 45" . The yarn is fed throughstepped cylindrical tube (hollow needle) kept at 45" tothe je t body. The yarn enters at an angle and contactsthe wall of the jet. The air is fed axially into the je t andpa sses around the feed needle an d forms a turbulentzone in the venturi. Loops and arcs introduced in the

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INDIAN J. FIBRE TEXT. RES., MARCH 1991

Air hole .Compressed

a ir

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(b) Taslon X '(c) Taslan X

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(d ) Toslan XI V (e ) loslon X V ( f ) Tasian X XFig. I- The converging-diverging type air texturing jets

process are locked in place when the yarn iswithdrawn from the turbulent zone at an angle of 90.The type IXjet was especially suitable for pre-twistedyams since a strong untwisting action was provided inthe venturi.

Type IX jet, however, had serious drawbacks .Firstly, the texturing speed was very low (10-50mjmin) and there were problems of uniformity,confining the process to the production of bulky andeffect yarns. Secondly, the twisting of the yarn beforeor after the je t was essential for obtaining a stable yamstructure; this increased the costs. Thirdly, the je t wasvery difficult to set and suffered from serious wearproblems.30

In 1960, Ta slan type X jet, which is shown in Fig.I(b), was introduced by Du Pont. In contrast to thetype IXjet, the yam in type Xjet enters axially. The airstream passes uniformly around the circumference ofthe yarn input channel. The needle extends into theopening of the nozzle through which the compressedair enters the so called turbulence chamber. Axialmovement of the needle alters the cross-sectionalarea of the clearance and has an influence on the airmass flow rate . An important feature of this texturingnozzle is the way in which the asymmetric flow profileis obtained. Uniform smooth flow ofcompressed ai ris disturbed by means of the eccentric setting of the je telement, thus the necessary turbulence and

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KOTHARI & TIMBLE: AIR-JET TEXTURING

Texturedyarn

" -Compressed air

Hema Jet co reFig. 2--C ore of a cylindrical type air texturing jet

asymmetric swirling are achieved. With this je t thetexturing speed was increased to 70-90 m/min and theexpensive cost of twisting was eliminated.A significant improvement in technologicalperformance was achieved by the introduction ofTaslan type XI je t in 1968. Although the yarn inputchannel and the nozzle were similar to those of type Xjet, modification of the air inlet was sufficient to resultin a vastly superior performance. r type XI je t, the airstream does not flow uniformly around the circumference of the needle but is fed through an inlet hole asshown in Fig. I(c). In other words, the flow from theair reservoirs to the needle tip is restricted to allowflow on one side of the needle only. The opening can bein the shape of a slit or any other shape. In comparisonwith the previous jets, end-to-end differencesbecame far more modest although the jets were still setthrough -trial and error but tthe operability wasconsiderably betterl.

Taslan type XI Mark IV jet , introduced in 1973 byDu Pont, allowed processing speeds to be increasedup to 500 m/min for a 167 dtex yarn. The constructionof type XI Mark IV jet is very similar to tha t of type XIjet except for the device used at the exit point of the jet.Thi s device is just a flap arrangement and has thefunction of increasing the vacuum effect and drawingextraneous loops into the body of the yarn I, thusimproving the uniformity and quality. The same yamcould only be textured at approximately 150 m/minwith type XI jct. Another improvement was in thequantity of air used for texturing. This, whencombined with high texturing speeds, resulted in avery significant reduction in air consumption perkilogram of yarn produced.A new je t Taslan type XIV was available by 1976.Fig. 1 d) shows the je t with the flap arrangement.Lower air consumption was achieved throughchanges made in the internal design of the air flow.

The Taslan type XV jet, shown in Fig. I(e), uses acylindrical baffie at a fixed dist ance from the je t exit.The air and yarn impinge onto the baffie and the yammoves around the lower surface of the baffie .Different sizes of baffie rods are provided by themanufacturer. A series of patents 2 from Du Pontdescribe the further developments related to theabove jets. Fig. 1(f) shows a section of the Taslan typeXXjet which has easy string-up feature with the helpof cam set-up provided. Type XXjet was particularlydeveloped for texturing fine denier yarns. However,at present , 'Mark XX Ease-A-Matic Jet' can handlea wide range of yarn deniers.Cylindrical jets are simpler in constructionconsisting of housing with simple trumpet-shaped jetcores without any adjustments . This type of je t wasintroduced in the 1950s in Czechoslovakia to makeMirlan yarns. A nozzle similar in construction wasintroduced by Heberlein Company in late 1970sunder the trade name HemaJet. As shown in Fig. 2, airis fed into the main duct of the nozzle by means ofanumber of small inlet bores where it impinges uponthe overfed supply yam . Three holes in the jet core canbe used for production ofcore/effect yams in additionto normal single and parallel-end textured yarns.They are suitable for relatively finer filaments (up to Idtex) and allow higher overfeed before the je tcompared to the equivalent single hole je t core.3 Properties of Air Textured Yarns and TestMethods

Air textured yarns have unique surface structureand greater bulk than the parent yams. As a result, thefabrics made from these yarns have subdued lusture,warmer hand and better covering power and thermalinsulation. Th e internal structure of the yarn is suchtha t the tenacity and initial modulus are substantiallyreduced and there is a certain amount of instabilitypresent in the macro structure of the yarn. Providedthe instability is not very high , the extension at peakload is reduced . Hot water shrinkage of these yarns isalso important from the point of view of processing offabrics made from these yarns. The measurementtechniq ues being followed at present to characterizethc air-jet textured yarn have a number of limitationsand considerable work is required to improve themethods of characterization of these yamsS - 8. Someimportant properties of air-jet textured yarns and thetest methods used widely in the industry for

d e ~ e r m i n i n g these properties are described below.3.1 Instability

If the loops of ai r textured yarns are pulled outduring further processing, the yarn bulk will be .

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INDIAN 1. FIBRE TEXT. RES., MARCH 1991

reduced and if this bulk reduction takes placeselectively in certain sections of the yarn, theirregularity of the product will be increased. Air-jettextured yarns are, therefore, tested for the stability oftheir structure . The Du Pont method9 is generallyused for the measurement of instability of air-jettextured yarns. The percenvage of permanentincrease in length, after a load of 0.33 g/den has beenapplied for 30 s to the yarn, is taken as a measure ofyarn instability.Instability (%) = [(L2- LillLd x 100where L( is the yarn length under a load of 0.01 g/den;a n d ~ , the yarn length (under a load of 0.01 gfden) 30 safter the removal of the heavier load (0.33 g/den).

Fig. 3 shows the laboratory set-up used formeasuring instability. This set-up allows 1m lengthfrom the top clamp to be marked initially at the lowerload. The heavier load is then added and retained for30 s duration after which it is removed. Thepercentage instability value can be read directly on ascale.3.2 Pbysical BulkThe measurement of the physical bulk of airtextured yarns according to Du Pont method9 isbased on the comparison of densities or specificvolumes of the packages of the parent yarn and thetextured yarn. The parent yarn and the textured yarnare wound on the same winding machine under thesame tension. The weight of the yarn wound on thepackage is measured and its volume calculated fromdiameter measurements . Physical bulk is thenobtained from the formula:Physical bulk (% ) = [(Parent yarn package density)/(Textured yarn package density)] x 1003.3 Hot Water ShrinkageThe measurement of shrinkage in hot water gives anidea about the dimensional stability of fabrics madefrom these yarns dur ing the finishing operations. Thelength of the air textured yam, La, is measured under avery low load of 0.0025 g/den and the yarn isimmersed fo r 25 min in a constant temperature waterbath maintained at 95 C. The yarn is then removedfrom the bath , allowed to dry for 24. h at roomtemperature and then the yarn length .L b , is measuredunder the same load of 0.0025 g/den. Finally, theshrinkage is calculated from the following formula:Hot water shrinkage (%) = [(La- Lb) / La]X 1003.4 Surface CharacteristicsThe structure of air-jet text ured yarns consists ofadistinct core with filament loops on the yarn surface.32

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KOTHARI & TIMBLE : AIR-JET TEXTURING

Chosl>nSl>C tion ( I)""" 1m m

Loop hl>ight =nLoopfrequl>ncy =T X 1000 loops/m

Fig. 4- Surface structure of an air-jet textured ya rn

taken as the breaking elongation. Knowing the lineardensity of the yarn being tested and its gauge length,the Ibad-elongation curve can be transformed to thestress-strain curve and the tenacity, initial modulusand breaking extension of the yarn can then bedetermined .3.6 Evenness Properties

The evenness properties can be assessed using theUster evenness tester. A yarn monitor withappropriate condensor slot is used at a speed of 100m/min to assess the CV % of mass per unit length .Neps per unit length are counted using an imperfectionindicator with a setting of 140% to identify neps.4 Experimental Procedure .

Five converging-diverging type jets, viz. Taslan X,XI, XIV, XV and XX , an d two cylindrical je ts, viz.HemaJet T 100 and T31 0, were used in the presentstudy with the aim of comparing the performance ofvarious jets. Tw o ends of 76 den /36 fil polyestermultifilament yarn were ai r textured together using33.3% overfeed, 9kg/cm 2 ai r pressure, 4.7 %mechanical stretch, 200C heater temperature and0.7% take-up underfeed at 300 m/min take-upspeed. The yarns were pre-wetted before texturingusing HemaWet system at a pressure of2 kg /cm 2 andwater consumption rate of I litre/h . Th e optimumtexturing conditions were obtained by adj usting theTaslan jets to get the maximum delivery andstabilizing zone tensions . Once the optimumconditions were obtained, the ai r textured yarn waswound on a new package and the package density wascalculated based on the mass of the total yarn wound

and the volume occupied by the yarn on the package .Untextured yarn (parent yam) was wound with thesame tension on a different package to obtain parentyarn package density . The textured yarn packagedensity and the pa rent yarn package density valueswere used to calculate the physical bulk of the airtextured yarn . HemaJets have fixed settings exceptthe baffle setting which is dependent on the denier ofthe yarn being produced . In stability (% ) is obtainedusing the Du Pont test method discussed earlier. Yamtenacity and breaking extension were obtained usingan Instron tensile tester. Uster CV (%) and neps/ lOOOm were obtained on Uster Evenness Tester UT I.

To study the effect of process parameters, nettoverfeed was varied between 10% and 30% at 8kg /cmz a ir pressure without heater; ai r pressure wasvaried between 6 kg/cm z and 10 kg /cm 2 at 20% nettoverfeed without heate r; and the heater temperaturewas varied between 150C and 210C at 20% nettoverfeed and 8 kg /cm 2 air pressure using HemaJetwith T 100 je t core . Nett overfeed is defined as thepercentage increase in yarn denier after texturingcalculated on th e bas is of pa rent yarn denier of2 x 76.

In add ition to obtaining the physical bulk ,instab ility (% ) and tensile properties as describedea rlier, yams were tested for ho t water shrinkage. Thest ructural parameters of the ai r textured yarns likecore diameter , loop size and loop frequency wereobtained using a Projectina microscope .5 Results and Discussion

Table 1 shows instability, physical bulk , tenacity,breaking extension , Uster CV and neps / IOOO m for

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INDIAN J. FIBRE TEXT RES . MARCH 1991

yarns produced using difTerent jets. Th e physical bul kof yarn s produced using HemaJet TIOO , HemaJetTJIO and Taslan XXjet is higher as compared to thephys ical bulk of yarns produced from other texturingje ts. HemaJet TIOO , HemaJet T310 and Taslan XXjet also produce yarns whose instability , brea kingextension, Uster CV and nep density are relativel ylower. The differences in tenacity of yarns producedusing different jets are no t significant. Thus , for theparallel-end tex turing o f 76 den/ 36 fil polyesteryarns, Hem aJets and Taslan XX jet produce yarns ofbetter quality as compared to the other Taslan je ts.

Table 2 shows the effect of overfeed, ai r pressureand heater temperature o n the properties of theair-jet textured ya rns. Increase in overfeed (%)increases the physical bulk , core diameter and loopfrequency but at the same time instability and loopsize also increase. There is also significant reductionin tenacity and modulu s and increase in breaking

extension with the increase in overfeed. It isimportant to have higher levels of overfeed to gethigher levels of physical bulk bu t after a certain levelof physical bulk , there is a significant reduction inother quality features like stability of ai r texturedyarns. These factors put a limit to the level of overfeedthat ca n be used .

Physical bulk a nd loop frequency increase whilethe insta bility and loop size reduce with increase in airpressure. Reaso nab ly high ai r pressures are req uiredto produce good quality yarns. However, with theincrease in ai r pressure the tenacity reduces and theyarns become more stiff as indicated by the hi ghervalue of modulu s. With the increase in heatertemperature , the stability of the yarn increases a ndthe residual hot wa ter shrink age reducessignificantly. Heating also reduces the loop size of theyarn.

Tahlc I p ~ r t i t ' of air -Je t t ~ x t u r ~ t l yam s p r o d u ~ e d using different jets wi th optim um se tting',Jet type In stabi lity Physical Tenacity Breaking Uster Neps/% bulk g/den extension CV % 1000 m% 0 0HemaJet TIOO O.Ll 192 2.3 ~ 5 . 4 7.12 40HemaJet T310 0. 12 ISS 2.4 2 U 6.13 20Taslan X 0.36 152 2.X 29.1 11 .62 360Taslan XI 0.35 ISS 2.6 27S 9.37 280Taslan XIV 02 2 165 2.5 273 9. 11 60Taslan XV 02 4 1(,0 2.6 26.2 X 15 120Tas lan XX 0.1 < Ig5 2.5 25 .6 70 2 40

Tahk 2 Elfect or processing parameters on the properties of air-jet textured yam sProcess In stabili,l y Ph ys ica l Hot wata Core Loop No. or Tenaci ty Breaking Initialparameter hulk h r i n k a g ~ d i a l l 1 ~ t e r SIZ,: loops/m g/tlen ex tension modulusc) pm pm 0;) g/den

Parent ya rn 100 7.2 IXS 4.31 30. 1 X3 .3Overfeed (0/. ,)

10 0.05 204 5.21 205 S6 1360 3.37 21.6 49.315 0.08 239 4 .X9 212 9X 1930 3.00 23 .7 42.520 0.1 5 290 4.67 215 lOX 3.190 2.72 26.3 29.225 O.XO nx OX 220 II X 5X60 2.49 27.6 IX630 2.24 297 4.01 226 130 6960 2.36 32 .2 9.4

Air pressure(kg/em' )6 0.23 250 4.35 216 1:19 ISSO 2.X4 25. 9 21. R7 O. IX 255 4.23 214 116 34 70 2.74 25.4 273S 0.15 27 0 4.67 215 lOS 33')0 2.72 26.3 29.29 0.13 274 4.50 217 X5 3670 2.70 26.0 30 .610 n. lo 2XI 4.7J 216 X2 41XO 2.60 26.2 31. X

Heater temp . eC )150 0.0') 263 H)5 20 1 X7 ,1270 2.76 235 36.2160 0.05 259 2.00 204 XS 3310 2.74 21 .. 39.1170 0.05 265 1.96 1')6 XI .1230 2. 77 21.6 3X.5Ixn 0.04 264 UQ 192 X3 3170 2.XO 20.0 41 .7190 0.03 266 UO 194 XO 3 150 2.7X 19 .2 43 .3

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KOTHARI & TIMBLE: AIR-JET TEXTURING

Table 3 shows the linear regression equationsbetween va rious air-jet textured yarn properties(except instability) and the percentage ove rfeed . Thelog values of instability were found to correlate betterwith the log va lues of overfeed. High correlationcoefficients (> 0.9) in each case indicate that linearregression eq uations given in the table can be used toestimate the various properties of ai r-jet texturedyarns processed wit h different values of overfeed.Tab le 3 a lso gives the standard errors of the Yestimates and the X coefficients .Tables 4 and 5 show the results of similar linearregression analysis between various air-jet textured

yarn properties and a ir pressure and heatertemperature respectively. Linear regressionequations between core diameter/breaking extensionand air pressure have relatively lower values ofcorrelation coefficients (Tab le 4). Correlationbetween other properties and ai r pressure is quitegood . Similar linea r regression ana lysis between airtextured yarn properties and heater temperature(Tab le 5) indicates that most of the properties arereasonably well correlated linearly with heatertemperature . Corre lation coefficient values ofphysical bulk and tenacity are, however, relativelylower.

Table J - Regression equations representing the effect of overfeed percentage on air-jet textured yarn properties (XI = overfeed %.10

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I DIAN 1. FIBRE TEXT. RES ., MARCH 199 1

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Fig. 7- Effect of overfeed. air pressure and healer temperature onproperties of air-jet textured yarns: (a) Tenacit y. (b) Breakingextension , and (el Initial modulus

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INDIAN J. FIBRE TEXT. RES . MA RCH 199 1

processing pa rameters, viz. a ir pressure an d heatertemperature . Figs 5(a), 5(c) a nd 6(a) indicate thathea t-se tting reduces instability, ho t water shrinkageand core diameter of the yarn . Increase in physicalbulk with the increase in a ll the three processparameters (Fig. 5a) may be expla ined as follows.With the increase in overfeed , the core diameter andloop frequency (Figs 6a and 6c) increase as a result ofwhich physica l bulk increases. Th e increase in bulkwith increasin g air press ure and hea ter temperature,on the other ha nd , is main ly du e to redu ction in loo psize (F ig. 6b) as smaller loops a re mu ch more rigid .The tenacity of air-jet tex tu red ya rn decreases withincrease in all the three process variab les (Fig . 7a).The breakin g extension increases considerably withincrease in overfeed (Fig. 7b) du e to the lower stabilityof yarns produced wit h higher ove rfeeds. However,the hea t setti ng tends to red uce the breakingextension considerably. The lowe r initia l modulus ofthe yarns produced with hi gher overfeeds (Fig. 7c) isalso du e to the lower structura l sta bility of theseyarns. Increase in a ir pressure and hea ter tempera tureincreases structural sta bility, th us producing yarns ofhigher initial modulus.6 Conclusions

A compariso n of different air texturing jetsindicates that some jets perform better than the othersfor a given feed yarn. For texturing the two ends of a 76den /34 fil ya rn together, HemaJe t T I 00 , HemaJetT310 and Ta slan XX show rela tivel y better perform-

3H

ance as compared to the o th er je ts. Air-j et texturedya rn properties like instab ilit y, physical bulk , hotwater shrinb ge, core di a meter , loop size, loopfrequency, tenacity, breaking extension an d initi a lmodulus are affected by process parameters suchove rfeed , air press ure and heate r temp e rature .Regression analysis shows tha t mos t of the propertiesof air-jet tex tu red yarns are linea rl y rela ted with theoverfeed, a ir pressure and heater temperature .Howeve r, a log-log relationship bet ween instabilit yand overfeed is observed. The effect of variousprocessing pa ramete rs on the properties of air-jettex tured ya rn s indicates th a t overfeed ha s muchgrea ter effect than the ot her iwo .process parameters,viz . air press ure a nd hea ter temperature.ReferencesI Price S T. Mod Tex t . 57( 7) (1976) 28.2 US Pat4.096.612(toE I Du Pont de Nemoufs&Co. lnc.) 27 June

1978 .3 US Pat4. 157.605 (to E I Du Pont de Nemours & Co . Inc.) 12June 197 1.

4 US Pat 4, 189,8 12 (to E I Du Po nt d e Nemours & Co. Inc .) 26February 1980.

5 Kothari V K, Sengupta A K , Rengasamy R S& Goswamy BC,Text Res 1,59 (1989) 317.

6 Sengupta A K. Kot har i V K & Alagirusamy R, Tex t Res 1 , 59(1989) 758.7 Sengupta A K. Koth a ri V K & Ren gasamy R S.

Chemiefasern / Tex t-Ind, 39/91 (1989) 111 2.8 Sengupta A K. Koth a ri V K & Ren gasamy R S.Chemiefa sem / Text- Ind , 40/92 (1990) 998.9 Du Pont Technical In/ormation Bulletin X-241 . March 1974.