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 DOI: 10.1177/004051750407400606

2004 74: 497Textile Research JournalYasemin Aydogmus Korkmaz and Hassan M. Behery

Drafting Dynamics of Fine Denier Polyester Fibers  

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Drafting Dynamics of Fine Denier Polyester Fibers

YASEMIN AYDOGMUS KORKMAZ1 AND HASSAN M. BEHERY

School of Material Science, Clemson University, Clemson, South Carolina 29634, U.S.A.

’Corresponding author: present address, Kahramanmaras SutcuImam University, Faculty of Engineering, Dept. of Textiles, 46100,Kahramanmaras, Turkey, email: ykorkmaz@ksu.edu.tr

ABSTRACT

It is important to understand the role of fiber properties in the drafting process. Finerdenier fibers may have different drafting behaviors than average denier fibers, such asdrafting force, required roller settings, draft distribution, and velocity change zone. Theobjective of this work is to study the interaction of specific fiber fineness values and thedrawing machine. Three different fine denier polyester fibers (0.8, 1.0, and 1.2) are run ona three-over-three roller drafting machine set at six different drafts with three rollersettings. A high-speed video camera system observes fiber movements and measures fiberspeeds in the drafting zone. In this study, fiber speed and variations in fiber speed aresignificantly affected by fiber fineness and drafting conditions. Fineness changes draftingbehavior by introducing fiber clusters and fiber contact points. The acceleration processdepends on the interaction of static and dynamic friction forces at the fiber contact points.Therefore, fiber movement in the drafting zone is not a continuous process, that is, itconsists of local acceleration and slowing down of segments of fibers.

Different methods have been used to observe fiber

drafting behavior. Taylor [9] used radio-activated woolfibers to determine the proportion of fibers that accelerateto the front roller speed at any given time. Over a largepart of the drafting zone, floating fibers achieve speedsgreater than back roller speeds for a limited time, andthey have only two speeds during their transfer throughthe drafting zone. Later, from a high-speed photographyexperiment, Taylor [ 10] confirmed that floating fibersachieve speeds intermediate between those of the backand front rollers.

McVittie and Barr [5] observed the movement ofcolored fibers in an apron drafting system with a micro-scope. They reported that the motion of floating fiberswas determined by frictional contact points with neigh-boring fibers, and the coefficient of friction betweenmaterials varied with speed.

Using treated fibers to measure fiber speed canchange a fiber’s surface characteristics. Moreover,placing these fibers on the sliver surface may disturbthe fiber’s behavior, preventing observations of actualfiber movement. In recent years, laser Doppler ane-mometer (LDA) has been used to measure fiber speedon different drafting systems [1, 12] with more accu-racy than previously mentioned methods, but monitor-

ing fiber interactions in the drafting zone is not pos-sible with LDA.

In this research, we use a high-speed camera to pro-vide very real fiber movement representations withoutchanging the sliver structure. Limited information isavailable describing the effects of fiber fineness on fiberspeed under different conditions. Therefore, the mainpurpose of our research is to investigate the effect of fiberfineness on fiber speed under various drafting conditionsprovided by different draft ratios and roller settings.

Experimental ProcedureThe polyester (PET) fibers used in the entire experi-

ment came from Wellman Inc., Charlotte, NC. The man-ufacturing company used the same processing proce-dures to manufacture three different deniers of the PET-0.8, 1.0, and 1.2-all with the same length of 38 mm.The fibers were in card sliver form. and the sliver weightwas 5 ktex.

This experiment was run at the main drafting zone ofa two-zone drafting system with three top rollers andthree bottom rollers. The experimental design consistedof three main factors: fiber fineness (0.8, 1.0, and 1.2

denier), six draft combinations (three total draft ratiowith two break draft ratio), and roller setting (43.7, 45,and 47 mm). At the break drafting zone, the roller settingwas 46 mm and break drafting ratios were 1.47 and 1.76with a constant 1.80 m/min incoming speed. The threetotal draft ratios used in the study were 6.07, 6.80, and7.73.

’

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498.

Four slivers were fed into the drawframe, and an

Olympus Encore 2000 model high-speed camera with amotion analyzer was used to record fiber movementalong the drafting zone. An endoscopic lens with its ownlight source connected to a high speed camera wasplaced directly over the drafting zone, and it was able tocapture up to 1000 frames per second. In each treatment,the camera was focused between two middle slivers and

placed very close to the front roller for the first two

replications and to the back roller sets for the second tworeplications in order to collect unbiased data.

During the recording, the camera setting was 500frames per second with 20 X shutter speed. The devicehad a limited memory, capable of storing 2.2 secondslong, the digital recording equivalent of 2046 frames.Therefore, the recorded pictures were replayed with fiveframes per second and re-recorded on s-vtts videocas-settes for further speed analysis.

Calibration was performed after every other four rep-lications with a steel ruler placed between rollers, and thepicture showing the ruler was recorded. This picture waslater played in still mode, and the lines of the ruler weredrawn on a transparency that was placed on the monitor.The screen was divided into four sections, each repre-senting 1 mm (Figure 1). Fifty readings per replicationwere taken at different sections of the monitor in order toscan the whole viewing area. The actual time duringwhich a chosen fiber traveled from the beginning of onezone to the end of the next zone (2 mm) was displayedwith 0.002 second increments on the motion analyzermonitor in order to calculate the fiber speed.

Data were tested by analysis of variance (nova), andmean separation was performed by the least significantdifference at P = 0.05 if the F test was significant at thesame level. The relative importance of each source ofvariation in the NOVA, including fiber fineness, draftratio, and roller setting, was determined by partitioningthe total sum of squares for treatments into main andinteraction effects and expressing the individual contri-butions to variation as a percentage of the total sum of

squares for the model.

. Results ,

,.

The average fiber speed in the main drafting zonedepended significantly on fiber fineness, which ac-

counted for 22% of total variation in fiber speed (TableI). Each fiber fineness level significantly differed fromthe others. The average fiber speed increased with in-creasing fiber fineness. The microfiber had a speed of9.95 m/min, while the 1.2 denier fibers had 7.64 m/minas an average (Table I).

FIGURE 1. Tracking a single fiber movement betweenthe two roller sets.

The draft combination had a significant influence onfiber speed, accounting for 18% of the total variation inaverage speed. In general, the average fiber speed in-creased with increasing total draft ratio. In addition, 16%of the total variation was attributed to the fiber finenessand draft combination interactions (Table I). The generaltrend for 0.8 and 1.0 denier fibers was that higher averagespeeds were measured at the draft combinations with1.76 breaking draft (Table II). However, the draft com-binations with 1.47 break drafting ratio yielded higherfiber speed readings for 1.2 denier fibers.The interaction of setting and draft ratio was a signif-

icant factor, which accounted for 7% of the total varia-tion, even though the main effect of setting was notsignificant (Table I). For each draft combination, fiber

speed remained generally unchanged with increasingroller settings from 43.7 to 47 mm. However, within eachroller setting, increasing the total draft ratio from 6.07 to7.73 increased fiber speed regardless of back draftingratio (Table III).

Fiber fineness and draft ratio significantly affected theC V% of speed, accounting for 10% and 9% of the totalvariation, respectively (Table I). In addition, fiber fine-ness significantly interacted with total drafting ratio, andthis interaction accounted for 13% of the total variationin CV% speed. The other factor that had a significanteffect on the CV% of speed was setting: increasing thesetting from 43.7 to 47 mm increased the variation inspeed.

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TABLE I. Sources of variation in the analysis of variance (NOVA) forthe effect of fiber fineness, draft ratio, and setting on the speed andCV% speed at the main drafting zone.

’Mean separation of each variable within rows and columns by leastsignificant difference at P = 0.05.

z

Discussion

In this study, we intend to show how different fiberfineness levels behave at different drafting conditions.The statistical analysis reveals that fineness has a signif-icant effect on the average fiber speed at the main rollerdrafting zone. Fineness introduces the clustering effectand different numbers of fiber contact points.

In roller drafting, several researchers have reportedfiber grouping behaviors [2, 3, 4, 8]. The size and num-ber of clusters depend on several factors such as fiberlength, crimp, spin finish, etc. In this study, these factors. were constant, except for the number of fibers in thecross section of a sliver, and fiber fineness, which canchange the number of fiber contact points. The number offibers in the cross section of microfiber card sliver was50% more than that of a 1.2 denier fiber card sliver.

Hence, the crowded structure of the microfiber sliverobviously increased the number of fiber contact points.The more direct effect of fiber fineness on the cluster

structure is bending rigidity, which depends on the shape

TABLE II. Interaction of fiber fineness and total drafting catio onspeed and CV9E speed at the main drafting zone.

’Mean separation of each variabie within rows and columns by leastsignificant difference at P = 0.05.

TABLE III. Interaction of roller setting and total drafting ratio onspeed and CV% speed at the main drafting zone.

’Means within rows and columns separated by least significantdifference at P = 0.05.

factor of the fibers and proportional to the fourth powerof diameter for round fibers [11]. Microfibers have alower bending rigidity, which allows them to bend orwrap more easily than coarser’fibers. Thus. the clustersformed by microfibers are more compact than the coarserfiber clusters due to the higher compression forces on thefibers created by flexible fibers [8]. The closer packing ofmicrofibers results in a higher number of contact points.

Drafting is a highly complex transformation of fibersbetween roller sets. As the fibers leave the back roller,the pressure on them starts to drop. The moment theyleave the back roller, internal tension in the fibers startsto restore crimp, which results in expansion of the

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sliver’s cross section in the drafting zone and formationof new interfiber contact points. At first, sections offibers in a slack position are straightened by openingcrimps with applied tension (Figure 1). The friction

forces at different directions cause fibers to stretch until

they lose contact with the other controlling contact

points. Subsequently, fiber sliding begins for a period oftime during which the forwarding force is higher than theretaining static friction force. During sliding, internal

tensions begin to restore crimp, creating new contactpoints (step 3 in Figure 1). This forward accelerationmovement is usually interrupted by either slow moving,unoriented fibers or other fibers in the clusters.

Each fiber contact point is exposed to a different

magnitude of friction force; the forces determine thelocal fiber acceleration and the drafting force. Betweenthe roller sets, friction forces on the different sections offibers vary because normal forces on the fibers are af-fected by the cluster structure and position in the draftingzone. Some fibers can be held firmly in clusters due tohigh entangling, which promotes higher static frictionforce by increasing normal forces at the fiber contactpoints. Additionally, the stick slip motion occurs at thefiber contact points when fibers are transferred from oneset of rollers to the next during drafting because thefriction coefficient varies as a function of load, velocity,and viscosity [6]. As a result, fiber movement in the

drafting zone is not a continuous process, but consists oflocal acceleration and slowing down of parts of fibers.This can explain the drafting behavior of different fiberfineness levels and what has been observed and reportedin this experiment and other studies.

Examining the video recordings, we saw sudden ac-celeration and deceleration of fiber sections. Addition-

ally, in roller drafting some of the fiber movements werenot perpendicular to the rollers. These phenomena havebeen observed by other researchers. Taylor [9, 10] con-firmed that fibers sometimes show sudden increases anddecreases in speed. Cherif et al. [1] reported that somefibers at the vicinity of the front roller have slower

speeds. Furthermore, some fibers have higher speed thanthe front roller speed, and fibers sometimes show suddenacceleration in the middle of the drafting zone [1, 12].

In our experiment, microfibers had the highest averagespeed, which decreased with increasing fiber denier.

However, variations in speed increased with increasedfiber denier. Clusters formed by coarser fibers have largevoid spots because of lower compression force and num-bers of fibers inside the clusters. This can ease fiber

acceleration and increase the variation in speed. On theother hand, most microfibers in clusters move togetherwithout changing their relative positions, resulting in adecrease in the speed variation. ’&dquo;

The drafting combination had a significant influenceon fiber speed. Increasing the drafting ratio from 6.07 to7.73 resulted in higher fiber speeds, The draft combina-tions with a break drafting ratio of 1.47 had relativelylower average speeds but higher variation values com-pared to the 1.76 break drafting ratio. This can be ex-plained by the fact that higher numbers of fibers suppliedinto the main drafting zone at the lower break draftingratio increased the number of fiber contact points andtherefore speed variation.From the statistical analysis, the 43.7 mm setting had

the lowest average speed, whereas 47 mm showed thehighest speed. Moreover, the variation in speed increasedwith increases in setting. At the 47 mm setting, the

spacing was large enough to release fibers from clusters,allowing them to have enough distance to accelerate andform new contact points, making more local accelerationpossible.

In conclusion, even though the differences betweenfiber fineness levels were small, the interaction of fine-ness with drafting conditions was highly important. Wefound that microfibers had the highest average speed butthe lowest variation compared to the other fineness lev-els. This change in denier was enough to change thefibers’ drafting behavior. Therefore, machine adjust-ments should be carefully made, especially when work-ing with fine denier fibers in order to spin high qualityyams.

ACKNOWLEDGMENTS

We would like to thank Wellman Inc. for supplyingthe test material and lending the high speed camera.Thanks are also due to Dr. Ahmet Korkmaz for criticallyediting the manuscript.

Literature Cited ’

1. Cherif, Ch., Achnitz, R., and Wulfhorst, B., New DraftingProcess Data on High Performance Cotton Drawframe,Melliand Textilber. 6, E-102-103 (1998).

2. Dehghani, A., Lawrence, C. A., Mahmoudi, M., Greene-wood, B., and lype, C., Fibre Dynamics in a Revolving FlatCard: An Assessment of Changes in the State of FibreMass during the Early Stages of the Carding Process, J.Textile Inst. 91, Part 1 (3), 359-373 (2000).

3. Grover, G., and Lord, P. R., The Measurement of SliverProperties on the Drawframe, J. Textile Inst. 83, 560-572(1992).

4. Komori, T., A Modified Theory of Fiber Contact in Gen-eral Fiber Assemblies, Textile Res. J. 64, 519-528 (1994).

5. Mc Vittie, J., and Barr, A. E., Fibre Motion in Roller andApron Drafting, J. Textile Inst. 52, T147-T156 (1961).

6. Nachane, R. P., Hussain, G. F. S., and Krishna Iyer, K. R.,

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Theory of Stick-slip Effect in Friction, Ind. J. Textile Res.23, 201-208 (1998).

7. Persson, B. N. J., "Sliding Friction—Physical Principlesand Applications," 2nd ed., Springer, Berlin, 2000.

8. Schoppee, M. M., A Poisson Model of Nonwoven FiberAssemblies in Compression at High Stress, Textile Res. J.68, 371-384 (1998).

9. Taylor, D. S., Some Observations on the Movement ofFibres during Drafting, J. Textile Inst. 45, T 310-322(1954).

10. Taylor, D. S., The Velocity of Floating Fibres DuringDrafting of Worsted Slivers, J. Textile Inst. 47, T 233-236(1956).

11. Warner, S. B., "Fiber Science," Prentice Hall, EnglewoodCliffs, NJ, 1995.

12. Wulfhorst, B., Weber, M., Phoa, T., and Lauber. M., Mea-surement of Fibre Velocity on a High-draft Drafting Sys-tem, ITB Yarn Fabric Form. 2, 37-39 (1994).

Manuscript received Sep(ember 18, 2002: accepted Jantww 23, 2003.

Bleachability and Dyeing Properties of Biopretreated and ConventionallyScoured Cotton Fabrics

A. LOSONCZI, E. CSISZÁR,1 AND G. SZAKÁCS

Budapest University of Technology and Economics, H-1521 Budapest, Hungary

O. KAARELA

Tampere University of Technology, FIN-33101 Tampere, Finland

’ To whom correspondence should be addressed: e-mail emi@muatex.mua.bme.hu

ABSTRACT

Enzymatic (cellulase, pectinase, xylanase) and simple buffer treatments in the presenceof a nonionic surfactant improve water wettability of fabrics to a level equal to conven-tional alkaline scouring. Caustic scoured fabric is significantly lighter and less coloredthan all the biopretreated samples. Application of a hydrogen peroxide bleaching subse-quent to the biopretreatment is beneficial because it reduces the great color differencesbetween conventionally scoured and biopretreated samples. Bleachability of the pretreatedfabrics is better than that of the conventionally scoured sample. Biopretreated fabrics canbe dyed with a reactive dye subsequent to the enzymatic treatment without furtheroxidative bleaching. At higher dye concentrations (i.e., 1 or 2%), there is no perceptiblecolor difference between the biopretreated and alkaline scoured fabrics in the dyed state.In pale and medium dyeings, however, the color difference is great and perceptible.Bleaching applied subsequent to bioscouring significantly decreases the color differencebetween the dyed samples pretreated in different ways. None of the pretreatments causesuneven dyeing. Wash fastness of the dyed samples is excellent and unrelated to the

pretreatment method.

Preparation and bleaching are among the most energy-and chemical-intensive steps in traditional cotton finish-

ing. About 75% of the organic pollutants arising fromtextile finishing come from the preparation of cotton

goods [5, 12]. Biopreparation may therefore be a valu-able and environmentally friendly alternative to harshalkaline chemicals for preparing cotton. In recent years,different enzymes, i.e., cellulases, pectinases, lipases,and proteases, have been tested for biopreparation [ 1, 2,10, 11, 14, 15]. We have demonstrated recently [3] thatxylanase enzymes can also be effective in removingnatural impurities from cotton.

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