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2005 75: 833Textile Research JournalYehia El Mogahzy, Ramsis Farag, Faissal Abdelhady and Asaad Mohamed

Interactive Fiber BlendingAn Integrated Approach to the Analysis of Multi-Component Fiber Blending. Part III: Analysis of

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An Integrated Approach to the Analysis of Multi-Component FiberBlending. Part III: Analysis of Interactive Fiber Blending

YEHIA EL MOGAHZY1, RAMSIS FARAG, FAISSAL ABDELHADY, AND ASAAD MOHAMED

Auburn University, AL 36849, U.S.A.

ABSTRACT

This paper represents the third of a three-part series in which multi-component fiberblending was analyzed using an integrated approach. The essence of this approach is thatthe phenomenon of fiber blending should be viewed on the basis of four basic modes ofblending: structural blending, attributive blending, interactive blending, and appearanceblending. In this part of the study, the focus is on interactive blending. A modified rotorring system is used in which the torque associated with opening and blending of a certainmass of fibers is monitored throughout its complete run. Blends of different cotton fibertypes and blends of polyester and cotton fibers are evaluated using a number of analyticalmethods such as the torque profile during opening and blending, the blend profile of torqueparameters, and the progressive change resulting from consecutive opening and blending.The results of this study revealed that when cotton fibers of different types are blendedtogether, fiber length and fiber fineness can influence interactive blending in such a waythat a great deal of the initial mechanical work done is consumed in opening and blendingthe longer and finer component in the blend. Large difference in fiber length and fiberfineness can result in a nonadditive and nonlinear maximum torque associated withblending. When cotton fibers are blended with polyester fibers, surface incompatibilitybecomes a more serious issue than fiber dimensional characteristics. In this regard, apossible failure of fiber cluster breakdown may occur, leading to nonlinear and nonaddi-tive interactive blending. The results also reveal that the propensity to opening of differentfiber types may follow different trends in consecutive processing.

In Part I [1] of this study, we introduced differentanalytical aspects that can collectively reveal the fullnature of fiber blending. In Part II of this study [3], wediscussed structural and attributive modes of blendingusing blends of different cotton fiber types and blends ofpolyester and cotton fibers. In this Part of the study, weshift our attention to interactive blending. This impliesthe interaction between fibers within a fiber componentand between different fiber components during theblending process. Understanding the nature of this inter-action can result in selecting appropriate fiber types andfiber attributes for a particular process and in optimizingmachine settings for particular blends. In addition, inter-active blending is often associated with many technolog-ical problems including: rough fiber flow, machine clog-ging, and breakage of fiber strands. These problems canhave a great impact on the consistency and quality ofblended end products [6, 8, 10].

Among all modes of fiber blending, interactive blend-ing is the least understood. This is due to its complexnature and the dynamic changes encountered when fibersof different types interact together during processing. Inpractice, this mode of blending is typically evaluatedthrough experimental trials involving actual processing(opening, carding or drawing) of fibers and subjectivelyevaluating the processing performance of fibers [7]. Mostfiber producers and machinery makers perform this typeof evaluation as an integral part of their quality controland design programs. This is typically a time-consumingtest as it involves a great deal of trial and error adjust-ments and corrections. In addition, it often lacks thequantitative measures that are necessary for product de-velopment and optimization. However, it serves as agood quality control tool for measuring performanceconsistency of fibers.

As indicated in Part I of this study [1], an optimuminteractive blending requires the fulfillment of two maincriteria: maximum breakdown of fiber clusters and ap-propriate cohesion between fibers. These two criteriaappear to be in conflict on the grounds that a complete

1 To whom correspondence should be addressed; e-mail: [email protected]

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breakdown of fiber clusters requires a smooth fiber in-teraction and virtually no fiber cohesion. However, anappropriate cohesion between fibers is required to main-tain the integrity of fiber flow during processing and toallow the formation of fiber strands. It is importanttherefore to analyze interactive blending in view of thesetwo criteria. In this part of the study, these two factorswere analyzed by measuring the propensity of a fiberstrand to opening and blending. Key questions addressedin this part of the study include:

What measures can we use to analyze interactive blend-ing?

How do dimensional characteristics such as fiber lengthand fiber fineness influence interactive blending?

What is the impact of fiber cohesion or fiber friction oninteractive blending?

What is the extent of meeting the linear-additive rule ofinteractive blending?

What is the effect of successive runs on interactiveblending?

Experimental Technique for EvaluatingInteractive Blending

In this study, we used a rotor ring unit to measure thepropensity of a fiber strand for opening and blending.This unit was used in several studies in the past [e.g. 4,5, 9, 11]. For the purpose of this study, the unit wasmodified substantially to allow pre-opening at the feed-ing stage using a wired clothed feed roll, and to permitreal-time monitoring of fiber flow during the blendingprocess so that a complete opening and blending profilecan be generated.

As shown in Figure 1, a torque couple was mounted onthe opening roll shaft to allow measuring the resistanceof fiber flow during opening. Torque and speed signalswere acquired using a data acquisition system and Lab-View� software system. Signal processing and analysisresulted in a torque profile or a stick-slip pattern charac-terizing the behavior of fiber flow during opening andblending. In addition, quantitative parameters such as themean torque and the opened web (band) width weremeasured. These parameters along with the torque profilecollectively characterize the propensity to opening andblending of the fiber sample.

Fibers in the raw or pre-opened form are fed to thefeeding roll by placing them on the feed plate and dis-placing them slowly until the front end of the fiber mat iscaught by the feeding roll. The feeding roll rotates clock-wise at a very slow speed (4 rpm) carrying the fibersstripped from the feed plate. A new wired feed roll wasused to allow a point-to-point opening action between

the feed roll and the opening roll. The opening rollrotates counterclockwise and open the fibers delivered bythe feed roll. The high rotational speed of the openingroll allows a great deal of opening. Opened fibers re-leased from the opening roll are delivered to the insidewall of the rotor via air suction. They are then condensedonto the inside wall of the rotor to form a fiber ring,which can be taken out of the rotor after completion ofthe opening process to be assessed, or re-fed again to thesystem for another run.

Torque Profile of Interactive Blending

As indicated above, the torque associated with open-ing and blending a fiber mass was monitored during theduration of each rotor-ring run. This resulted in generat-ing a torque profile, or a torque–time relationship. Weshould point out that all blend trials performed in thisstudy represented intimate blending in which raw fibersof each fiber type were manually pre-opened to formsmall fiber tufts and manually pre-blended by weightdepending on the desired blend ratio. The fiber mass wasthen fed to the rotor ring via a feed plate. As a result, theinitial manually blended fiber mass was in a rough formof a discrete fiber strand, which typically consisted ofdisorderly small fiber clumps. As a result, the torqueprofile produced from the first rotor-ring run exhibited anerratic and often unpredictable pattern.

The output material of the first run was a thick fiberring of a narrow width, when opened, resulting from thecondensation effect into the rotor. This ring was cut atone cross-section to create a fiber strand, which was thenre-fed to the rotor-ring to perform a second run. Thisprocedure was repeated to perform subsequent runsthrough the rotor ring. Repeated runs through the rotorring yielded more homogenous fiber strand and moreconsistent torque profiles.

To ascertain consistency and high reproducibility,torque profiles produced during the fifth rotor-ring runwere considered for blending analysis and comparativeanalysis between different fiber types. Figure 2 shows thegeneral shape of the torque profiles produced during thefifth rotor-ring runs. The initial zone of the torque profileis a no-load zone. This begins at the moment the fiberstrand is placed on the feed plate and ends when thefibers begin to transfer from the feed roll to the openingroll.

After the initial zone, the torque profile can be dividedinto three primary periods. The first period of the profile(period #1) reflects the initial resistance to the openingprocess by the newly fed fiber strand. The rise in torquein this period is a result of the resistance to the progres-sively increasing fiber mass removed from the feed roll

834 TEXTILE RESEARCH JOURNAL




to the opening roll. This rise continues until it reaches amaximum point at which the maximum amount of fibersper strand cross-section is being opened. A stick-slippattern in this period typically reflects a combination of

inter-fiber friction and fiber-metal friction. However, thefiber-metal friction dominates this period. The slope (tan�), which may be termed “initial opening stiffness” re-flects the initial resistance of fibers to opening; a high

FIGURE 1. Modified rotor ring.

FIGURE 2. Torque profile of fiber blending andassociated parameters.

DECEMBER 2005 835




angle (�) indicates high initial opening stiffness. Themaximum torque (Tmax) in this period reflects the initialtorque threshold of the fibers being opened.

The second period of the torque profile (period #2)represents a quasi steady-state condition of fiber opening.From a technological viewpoint, this is the most impor-tant period. The stick-slip pattern in this period indicatesa combination of fiber friction and fiber resiliency. Thefriction component here is largely dominated by inter-fiber friction. This pattern is characterized by the meanand the variance of the torque associated with openingthe fibers (Tm, �2

T).The third period of the profile (period #3) is associated

with a torque reduction resulting from clearing the feedroll from fibers and fiber transfer from the opening roll tothe rotor. Occasionally, at the end of the second periodand as the fibers are transferred to the rotor, a significanttorque peak may exist, which in some cases may begreater than the first peak. This peak may be a result ofhigh fiber–metal friction with the metal being the emptyfeed roll wires and the fibers are those carried by theopening roll. In typical processing, this high torque doesnot exist as a result of the continuous throughput andtransfer from one opening stage to another. Accordingly,the second torque peak and the torque reduction period(period #3) will be ignored in our analysis.

Results and Discussions

COTTON/COTTON BLENDS

The analysis of interactive blending involved threetypes of cotton: long-fine (LF) upland cotton, short-

coarse (SC) upland cotton, and extra long staple (ELS)Giza70 cotton. Values of fiber properties of these cottonswere presented in Part II of this study [3] and are sum-marized below.

�ELS LF SC

Mic 3.9 3.6 5.6UHML 1.43 1.32 1.06

SFI 3.2 6.5 11.6Str 48 40.4 29Elo 4.6 4.3 5.0Fin 148 145 200ML 0.97 0.90 0.87

�Figure 3 shows the torque profiles of the LF/SC cottonblend. These profiles clearly indicate that the SC cottonexhibits a torque level that is distinctly lower than that ofthe LF cotton. This is largely attributed to the expectedlower inter-fiber cohesion of the SC cotton in compari-son with the LF cotton as a result of its shorter length andsmaller number of fibers per cross-section of the fiberstrand. This means that dimensional characteristics offibers such as length and fineness can indeed influencethe propensity to opening. The extent of this influencewill be clarified later in this paper. Quantitatively, the SCcotton has lower values of opening stiffness, maximumtorque and mean torque than the LF cotton.

At 50%LF/50%SC, there is a rapid rise in the initialpart of the torque profile leading to higher initial openingstiffness and higher maximum torque than the individualblend components (100%LF or 100%SC). This rapid risewas very consistent in all the replicates made on thisblend. Based on evaluation of the appearance of blended

FIGURE 3. Torque profiles of the Long Fine/Short Coarse (LF/SC) cotton blend.





fiber webs, this high initial torque rise was found to belargely related to a loss of intimacy in the incoming fiberstrand with some LF and SC cotton fibers still formingclustered groups. This explanation was supported by theresults obtained from subsequent rotor-ring runs whichshowed that the initial opening stiffness of the 50%LF/50%SC blend progressively decreased in subsequentruns indicating an effect of interactive heterogeneity ofthe two fiber types. In the second period of the profile the50%LF/50%SC blend assumes an intermediate level be-tween the individual blend components.

Figure 4 shows the torque profiles of the ELS/LFcotton blend. These profiles indicate that the ELS cottonexhibits a torque level that is distinctly higher than thatof the LF cotton. This is partially attributed to the ex-pected higher inter-fiber cohesion of the ELS cotton incomparison with the LF cotton as a result of its longlength. Quantitatively, the ELS cotton has higher valuesof opening stiffness, maximum torque and mean torquethan the LF cotton. At 50%ELS/50%LF, the torque pro-file exhibits an intermediate level between those of theindividual components.

A different approach to analyze the blending perfor-mance, which was discussed in Part I of this study [1] isto examine the deviation of torque of the actual blendsfrom the linear additive law of blending. Figure 5 showsblend profiles of torque parameters for the LF/SC andLF/ELS blends. Note that the linear additive law wasapplied using the blend proportion by number as ex-plained in Part II [3]. Figures 5a and b indicate that bothcotton blends exhibited a linearly-additive mean torque.Since the ideal blend profile is based on the fiber pro-portion by number, it is clear that dimensional charac-teristics such as length and fineness can influence thepropensity to opening of the cotton fiber blend. Figure 5c

shows that the maximum torque of the LF/SC blendexhibited a clear deviation from the linear-additive rule.Figure 5d shows that the ELS/LF blend was additive butnonlinear. This makes the mean torque more suitable forcharacterizing the interactive nature of blending thanother torque parameters as it reflects the steady-stateprocessing condition.

Another aspect of interactive blending stems from theeffect of successive runs on the propensity to openingand blending. Figure 6 shows the mean torque and theopened web width at different rotor-ring runs for the twocotton blends discussed above. These results indicate thatsuccessive runs of cotton fiber blends result in progres-sive reduction in the mean torque and progressive in-crease in the web width. The torque results are generallyexpected on the basis that consecutive runs result in moreopening, better fiber alignment, and consequently lowerresistance to opening. The progressive increase in bandwidth is a result of the progressive increase in the degreeof opening. This is also an indication of progressive fibercluster breakdown. Obviously, a larger number of fibersand longer fiber length result in a larger width of the fiberweb.

The results of Figure 6 also indicate that the meantorque and the web width of the 50/50 blends wereintermediate between the values of the individual com-ponents. However, the change in both the torque and theweb width was not linearly related to the blend ratio. Forinstance, Figure 6a shows a bias of torque toward the SCcotton and Figure 6c shows a bias of band width towardthe LF cotton.

In light of the above results, it follows that whencotton fibers of different types are blended together, fiberlength and fiber fineness can indeed influence interactiveblending in such a way that a great deal of the initial

FIGURE 4. Torque profiles of the Extra LongStaple/Long Fine (ELS/LF) cotton blend.

DECEMBER 2005 837




mechanical work done (opening stiffness) is consumedin opening and blending the longer and finer componentin the blended fiber strand. Large difference in fiberlength and fiber fineness (e.g. the case of LF/SC blend)can result in a non-additive and nonlinear maximumtorque (or the torque required to initiate blending andopening). However, the surface and crimp compatibilityof cotton fiber blends result in an additive and linearmean torque. This means that blending of cotton fibers ofdifferent types is largely governed by the fiber separationmechanism. Obviously, exceptions to these findingsshould be expected if one or more of the cotton compo-nents in the blend exhibit abnormal surface characteris-tics such as fiber stickiness or high variation in waxpercent [5].

Cotton/Polyester Blends

Following the procedures discussed above, we exam-ined the torque profiles of some cotton/polyester blends.

Polyester fibers used are those that were examined inPart II of this study. Values of some of the basic char-acteristics of these fibers are given below and theirtorque profiles are shown in Figure 7.

�Property LP BP

Mean Length�inch� 1.38 1.07Fineness�millitex� 188 105Crimp extension % 26 37

�As shown in Figure 7, the two types of polyester fibersexhibited different levels of torque parameters. The longpolyester (LP) had higher torque level than the blackpolyester (BP). Based on the values of fiber characteris-tics of the two fibers, the BP has more fibers per unitweight and higher crimp than the LP fibers. These shouldhave resulted in higher torque values. However, the LPfiber has a longer length than the BP fiber. In addition, itexhibited higher fiber friction as shown in Table I, whichshows values of fiber friction of the different fibers

FIGURE 5. Comparison between actual and linear (by number) blend patterns of cotton blends.





examined in this study measured independently using theAuburn Beard Friction Test [2]. This method revealsfrictional values that strictly reflect the surface behaviorof fibers, independent of fiber dimensions.

Figure 8 shows the torque profiles of the LF/LP blend.As can be seen in this Figure, the LP fiber exhibitedsubstantially higher torque level than the LF cotton fiber.This is also supported by the higher values of quantita-tive torque parameters of the LP fiber over those of theLF fiber. This trend is largely attributed to the longerlength and the higher friction of LP fiber in comparisonwith the LF fiber; this is despite the larger number offibers per unit weight of the LF fiber over that of the LPfiber resulting from its fineness [3].

The 50%LP/50%LF blend showed an intermediatetorque level between the two individual components.However, there was a clear bias to the LF component.One reason for this bias is the larger number of fibers of

the LF component in comparison with the LP componentin the blend (66 to 34%). Another reason stems from thesubstantially higher friction of LP fiber over that of LFfiber. This effect is expected to hinder the cluster break-down of LP fibers leading to a propensity to opening ofthe blend that is merely a result of fiber separation of theLF cotton fiber.

The extent of meeting the additivity and linearitycriteria is demonstrated in Figure 9 for three of the torqueparameters, namely: mean torque, torque slope and max-imum torque. Note that the linear-additive law was ap-plied using the blend proportion by number as explainedin Part II [3]. As can be seen in Figure 9, the mean torquelargely met the additivity rule, but a great deal of biastoward the LF fiber is observed. On the other hand, themaximum torque and the slope (or opening stiffness)showed a clear bias to the LP component. This biassupports the speculation made earlier regarding the effect

FIGURE 6. Mean torque and band width at different rotor-ring runs of cotton blends.

DECEMBER 2005 839




of interfiber friction of the LP fiber since a bias in thesetwo parameters to one component typically implies workconsumed in attempting to break down fiber clusters.

This is particularly true when the bias is not due todimensional bias or a greater number of fibers per unitweight.

The effects of successive runs on the propensity toopening and blending of the LF/LP blend are shown inFigure 10. The two fiber types exhibited different behav-iors in successive runs through the rotor ring. While themean torque associated with the LF cotton fiber de-creased with successive runs, the LP fiber had a tendencyto initially increase and then level off in further runs.These trends were found to be consistent for each poly-

FIGURE 8. Torque profiles of the LP/LFpolyester/cotton blend (fifth RR run).

FIGURE 7. Torque profiles of two differentpolyester types.

TABLE I. Beard maximum friction values of different fibersat 6 psi lateral pressure [2].

LP BP ELS LF SC

F-F Friction (gr) 68 50 34 35 36F-M Friction (gr) 54 36 25 27 28

LP, long polyester; BP, black polyester; ELS, extra long staple Giza70cotton; LF, long-fine upland cotton; SC, short-coarse upland cotton.





ester fiber type examined in this study. The LP/LF blendfollowed the LF fiber trend and it was biased in value tothe LF fiber. The web width of the LP fiber decreasedprogressively with successive rotor ring runs. On the

other hand, the LF fiber increased with successive rotorring runs. The LP/LF blend was biased to the LP fiber.

The second cotton/polyester blend considered in thisstudy was the LF/BP blend evaluated in Part II [3] in thecontext of structural and attributive blending. It repre-sents an actual fiber blend utilized in textile processing toproduce special-effect fabrics. We should point out thatthe particular Black Polyester fiber used in this blendresulted in an unexplained blending irregularity when itwas blended with cotton fibers in an actual mill opera-tion.

Figure 11 shows the torque profiles of the LF/BPblend measured during the fifth rotor-ring run. As can besee in this Figure, the BP fiber exhibited lower torquelevel than the LF fiber. This was somewhat surprising inview of the fact that the BP fiber has more fibers per unitweight and higher fiber friction than the LF fibers. Unlikemost of the fiber torque profiles examined in this study,the BP fiber torque profile exhibited early torque peaks inthe no-load zone. Close examination of these peaks re-vealed that they were a result of a low coherence in theBP fiber strand leading to few clusters of fibers acceler-ating through the feed roll and entering the opening rollerearlier than the remaining fiber strand. The second periodof the BP fiber torque profile was characterized by apronounced periodicity that almost replicated the period-icity shown in the no-load zone. In addition, the torquelevel was not horizontal, as in most fiber profiles. In-stead, it had an obvious nonlinear dip between the firstpeak and the second peak.

Visual examination of the BP web after each runrevealed an interesting change; the web suffered progres-sive clustering and increase in irregularity. This indicatesthat the work done to open the BP fibers was merely aresult of opening the input web into fiber clusters ratherthan individual fibers. The presence of fiber clustersresulted in a web incoherence, which was not witnessedin other polyester and cotton fiber types.

The 50%LF/50%BP blend had an initial steep rise intorque leading to a higher initial opening stiffness andhigher maximum torque than the individual components.Following this initial trend, the blend was clearly biasedto the LF cotton values. Recall that the BP fiber has fiberfineness of 105 millitex and mean fiber length of 1.07inch and LF cotton has fiber fineness of 145 millitex andmean fiber length of 0.90 inch. This means that the50%LF/50%BP by weight is actually 46%LF/54%BP bynumber. This clearly means that the bias of the blend tothe LF fiber was not attributed to geometrical or quan-tity advantage of the LF fiber. Instead, the BP fibersfailed to fully intermingle with the LF fiber leading to atorque profile largely reflecting the LF fiber propensity toopening.

FIGURE 9. Linearity and additivity of different torque parameters ofthe LP/LF polyester/cotton blend.

DECEMBER 2005 841




Figure 12 shows the mean torque and web width of theLF/BP blend in subsequent rotor-ring runs. As can beseen in this Figure, after the first rotor-ring run, succes-sive runs resulted in a continuous increase in torque anda continuous decrease in web width of the BP fiber. Themean torque of the 50%LF/50%BP blend was biased tothe LF fiber in all successive runs. Meanwhile, the webwidth of the 50%LF/50%BP blend was biased to the BPfiber.

The extent of meeting the additivity and linearitycriteria of the LF/BP blend is demonstrated in Figure 13for three of the torque parameters, namely: mean torque,torque slope and maximum torque. Again, the linearadditive law was applied using the blend proportion bynumber as explained in Part II [3]. As can be seen inFigure 13, all torque parameters showed clear violationof the linear-additive rule.

In light of the above discussion, it follows that whencotton fibers are blended with polyester fibers, surfaceincompatibility becomes a more serious issue than fiberdimensional characteristics. For example, the case ofLF/LP blend discussed above clearly revealed that thehigh inter-fiber friction of the polyester fiber associatedwith high crimp resulted in fiber clustering and persis-tence of polyester fibers to stick together. Indeed, ap-pearance blending analysis showed persistent clusters ofthe LP component in the final fiber strand. The substan-tially higher torque variance of the LP component alsosupports this view. As a result, the mean torque waslargely biased to the LF component indicating that mostof the work done was consumed to individualize thefibers in the LF component.

The LF/BP blend represented an exceptional case inwhich both additivity and linearity were violated. Thesetrends were a result of a significant clustering effect thatwas evident by the web appearance and the high torquevariance.

Closing Remarks

In this Part of the study, the focus was on the analysisof interactive blending. This mode of blending primarilyreflects the propensity to opening and blending whenfibers of the same type or of different types are intimatelyblended together. In theory, the process of fiber openinginvolves two main mechanisms: fiber cluster breakdownand fiber separation or individualization. These twomechanisms are typically activated in a simultaneousmanner. Cluster break down is a result of consecutiveseries of opening in which larger fiber clusters, typicallyof the same type of fiber, are reduced to smaller ones.Fiber individualization is a fine opening process in which

FIGURE 10. Average values of net torque and band width of LF/LPblend in subsequent rotor-ring runs.





the primary effects are fiber separation and reshuffling ofindividual fibers of different fiber types.

The performance of these two mechanisms is largelydetermined by a number of factors some of which aremachine-related and others are material-related factors.Machine-related factors include machine settings, andthe number of consecutive operations. Material-relatedfactors include fiber dimensional characteristics such asfiber length and fiber fineness, and fiber surface charac-teristics.

The extent of failure of fiber cluster breakdown can berealized from the deviation of the mean torque blendprofile from the linearity and additivity criteria. Hightorque variance in one of the components of the blend isalso an indication of fiber clustering. Another way todetermine the extent of cluster breakdown is throughexamining the mean torque and the width of the fiberweb over a number of consecutive runs. A progressivereduction in the mean torque accompanied by an increasein the web width indicates a great deal of cluster break-down and fiber individualization. On the other hand, adwelling effect or progressive increase in torque associ-ated with a reduction in web width implies failure ofcluster breakdown.

Among the parameters used to characterize interactiveblending, the mean torque measured at the steady-statecondition proved to be the most reliable measure. This isdue its high reproducibility and its simulative nature ofactual opening and blending operations. Other torqueparameters such as maximum torque, initial slope, andtorque variance are useful in revealing interactive blend-

ing problems such as failure of cluster breakdown andinconsistency in the blended fiber structure.

Based on the results of this study, it was found thatwhen cotton fibers of different types are blended to-gether, fiber length and fiber fineness can influence in-teractive blending in such a way that a great deal of theinitial mechanical work done (opening stiffness) is con-sumed in opening and blending the longer and finercomponent in the blended fiber strand. Large differencein fiber length and fiber fineness (e.g. the case of LF/SCblend) can result in a nonadditive and nonlinear maxi-mum torque (or the torque required to initiate blendingand opening). However, the surface and crimp compat-ibility of cotton fiber blends result in an additive andlinear mean torque. This means that blending of cottonfibers of different types is largely governed by the fiberseparation mechanism. Obviously, exceptions to thesefindings should be expected if one or more of the cottoncomponents in the blend exhibit abnormal surface char-acteristics such as fiber stickiness or high variation inwax percent [5].

When cotton fibers are blended with polyester fibers,surface incompatibility becomes a more serious issuethan fiber dimensional characteristics. For example, thecase of LF/LP blend discussed in this paper clearlyrevealed that the high inter-fiber friction of the polyesterfiber associated with high crimp resulted in fiber cluster-ing and persistence of polyester fibers to stick together.Indeed, appearance blending analysis showed persistentclusters of the LP component in the final fiber strand. Thesubstantially higher torque variance of the LP component

FIGURE 11. Torque profiles of the LF/BP blend(fifth RR run).

DECEMBER 2005 843




FIGURE 12. Mean torque and band width of LF/BP blend insubsequent rotor-ring runs.

FIGURE 13. Linearity and additivity of different torque parameters ofthe BP/LF polyester/cotton blend.





also supports this view. As a result, the mean torque waslargely biased to the LF component indicating that mostof the work done was consumed to individualize thefibers in the LF component.

The LF/BP blend represented an exceptional case inwhich both additivity and linearity were violated. Thesetrends were a result of a significant clustering effect thatwas evident by the web appearance and the high torquevariance.

ACKNOWLEDGEMENT

The authors of this series of papers would like to thankthe National Textile Center (http://www.ntcresearch.org/) for sponsoring this research over a period of threeconsecutive years. A cosponsor of this research wasCotton Incorporated of the U.S.A. (http://www.cottoninc.com), which sponsored this research both financially andby providing many useful guidelines. We specificallythank Mr Charles H. Chewning, Jr, Mr J. Berrye Wor-sham, III, and Dr Preston E. Sasser of Cotton Incorpo-rated for their great support. We would also like to thankWelman Inc. and Dr Subhas Gosh of the University ofEastern Michigan (Former Research Director of ITT) forproviding the specially made polyester fibers used in thisstudy. Last, but certainly not least we would like to thankDr Radhakrishnaiah Parachuru of Georgia Tech and DrRoyal Broughton, Jr. of Auburn University for theirsupport and guidance in this study.

Literature Cited

1. El Mogahzy, Y. E., An Integrated Approach to the Anal-ysis of Multi-Component Fiber Blending. Part I: AnalyticalAspects, Textile Res. J. 74(8), 701–712 (2004).

2. El Mogahzy, Y. E., and Broughton, R., A New Approach

for Evaluating the Frictional Behavior of Cotton Fibers.Part I: Fundamental Aspects and Measuring Techniques,Textile Res. J. 63(8), 465–475 (1993).

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