The effect of short fibre and neps on Murata vortex spinning

subjected to extended pilling tests to againhighlight the <strong>effect</strong>s <strong>of</strong> elevated <strong>short</strong> <strong>fibre</strong>.FIBRE QUALITY CHARACTERISTICSSince growing location <strong>and</strong> conditions includingharvesting were identical, the differences in <strong>fibre</strong>properties can be attributed to module storage<strong>and</strong> gin heat. As expected, micronaire, <strong>fibre</strong>fineness <strong>and</strong> maturity were unaffected by the gintreatments. But length, strength, trash <strong>and</strong> nepcharacteristics were significantly affected by thecombination <strong>of</strong> storage moisture <strong>and</strong> gin heatconditions.FIGURE 6: MVS yarn tenacityFibre length characteristics<strong>The</strong>re were pronounced differences in staplelength, <strong>short</strong> <strong>fibre</strong> index <strong>and</strong> length uniformitybetween gin treatments (see Figures 1, 2 <strong>and</strong> 3).In general, seed cotton ginned with no heat inthe gin produced longer, more even cotton.Moist seed cotton ginned with no heat (MZ)produced the longest, most even cotton followedby dry seed cotton treated with zero heat (DZ).On the other h<strong>and</strong>, dry seed cotton treated withhigh heat (DH) <strong>and</strong> seed cotton stored underambient conditions <strong>and</strong> treated to st<strong>and</strong>ard heat(AS) produced lint with reduced staple length<strong>and</strong> higher <strong>short</strong> <strong>fibre</strong> contents.FIGURE 7: MVS yarn imperfections (Ne30/1 only)StrengthFibre strength is a fundamental <strong>fibre</strong> propertythat decides both yarn <strong>and</strong> fabric quality <strong>and</strong>processing efficiency. Fibre strength across alltreatments was generally very good (more than29 grams per tex) <strong>and</strong> in keeping with the grade<strong>of</strong> the cotton ginned. As expected, <strong>fibre</strong> strengthdid not vary greatly between gin treatments,although measurements were higher fortreatments stored under moist conditions (MZ<strong>and</strong> MH).FIGURE 8: MVS yarn hairinessTrash <strong>and</strong> <strong>neps</strong>Trash <strong>and</strong> <strong>fibre</strong> entanglements, such as <strong>neps</strong>,disrupt the spinning processes <strong>and</strong> damage bothyarn <strong>and</strong> fabric appearance. <strong>The</strong>se contaminantsmay be less <strong>of</strong> a problem in MVS spinningbecause <strong>of</strong> the suction around the MVSstationary spindle. As well as removing <strong>short</strong>er<strong>fibre</strong>s, the vacuum removes <strong>neps</strong> before they areFIGURE 9: Fibre lost during spinning

end uses.Two yarns counts were spun (Ne 30/1 <strong>and</strong> Ne40/1). Murata vortex spinning frames can spinyarn counts from carded sliver in the range fromNe 10/1 to Ne 50/1. Yarn was spun in sufficientquantities for thorough yarn <strong>and</strong> fabric testing<strong>and</strong> calculation <strong>of</strong> spinning efficiencies <strong>and</strong> <strong>fibre</strong>loss.Yarn tenacityYarn tenacity is determined by a combination by<strong>fibre</strong> fineness, <strong>fibre</strong> length <strong>and</strong> <strong>fibre</strong> strength. As<strong>fibre</strong> fineness was constant in this trial, the yarntenacity results reflect the gin treatments <strong>and</strong>their <strong>effect</strong> upon <strong>fibre</strong> length <strong>and</strong> strength.<strong>The</strong> MZ treated cotton produced the highesttenacity yarn in both Ne 30/1 <strong>and</strong> Ne 40/1counts, while the AS <strong>and</strong> DH treated cottonproduced the weakest yarns (Figure 6). Likewise,yarn elongation was better in the MZ treatedcotton <strong>and</strong> worse in the drier, heat-treatedsamples.<strong>The</strong> overall tenacity <strong>of</strong> the MVS yarns was betterthan that <strong>of</strong> comparative open-end rotor yarnsbut weaker than that <strong>of</strong> ring spun yarns.Yarn evenness <strong>and</strong> imperfections<strong>The</strong> evenness <strong>of</strong> yarn spun on all <strong>short</strong>-staplespinning systems is directly affected by <strong>short</strong><strong>fibre</strong> content. Evenness results followed a similarpattern to tenacity results, in that evenness wasbetter in yarns spun from cotton treated to moiststorage or zero heat. This was evident in bothyarn counts <strong>and</strong> was also reflected in thick <strong>and</strong>thin place counts (see Figure 7).But nep counts did not follow this pattern. DZtreated cotton had the lowest number <strong>of</strong> yarn<strong>neps</strong> in both yarn counts but AS cotton producedmore <strong>neps</strong> in Ne 30/1 yarn <strong>and</strong> MZ producedmore <strong>neps</strong> in Ne 40/1 yarn. It is interesting tonote that nep levels in both yarn counts were atleast 75 per cent better than yarn nep levels incarded ring spun yarns. Even yarns with thehighest yarn nep measurements (MZ <strong>and</strong> AS) fellwithin the lowest 25 per cent <strong>of</strong> all Uster Statisticentries for carded ring spun yarn <strong>neps</strong>.

Yarn hairinessYarn hairiness is significantly affected by <strong>short</strong><strong>fibre</strong> <strong>and</strong> the trial results follow a similar patternto the yarn tenacity <strong>and</strong> evenness results. BothMZ <strong>and</strong> DZ treated cotton, which had relativelylow levels <strong>of</strong> <strong>short</strong> <strong>fibre</strong>, had the lowest hairinessvalues in both yarn counts, while AS <strong>and</strong> MHcotton produced the highest hairiness values inboth yarn counts (see Figure 8).Fibre lossFibre loss at the MVS twist zone due to thevacuum around the base <strong>of</strong> the stationaryspindle will be an important issue in themarketability <strong>of</strong> Australian cotton to MVSspinning mills. Fibre losses, expressed as apercentage <strong>of</strong> the total input weight, weresignificant <strong>and</strong> greater for the cottons exposed todry storage <strong>and</strong> excessive heat during ginning.Figure 9 illustrates the <strong>fibre</strong> loss for each yarncount due to each gin treatment. As expected,MZ cottons lost less <strong>fibre</strong> while cottons subject toharsher treatments — for example AS <strong>and</strong> DHcotton — lost more <strong>fibre</strong>. Different nozzlegeometry <strong>and</strong> pressures can be used to reducethese figures although alteration <strong>of</strong> suchspinning parameters may cause significantchanges in yarn properties.Spinning breaksSpin breaks are defined as the number <strong>of</strong> breaksper hour per spinning frame. Sixty breaks perhour is considered the cut <strong>of</strong>f if a spinningefficiency <strong>of</strong> above 90 per cent is to be achieved.Spinning breaks for Ne 30/1 yarn were similarfor all gin treatments. <strong>The</strong> high end-break ratewith the DZ treatment was attributed to thecondition <strong>of</strong> the sliver (see Figure 10).Spinning breaks increased when the yarnbecame finer with all Ne 40/1 yarn exceeding 60breaks per hour per machine. But the MZtreatment had the lowest number <strong>of</strong> end breaks(64) while the DH treatment had the highest(96). <strong>The</strong> high number <strong>of</strong> breaks is evidence thatNe 40/1 may <strong>effect</strong>ively be the spin limit forcarded Australian cotton <strong>and</strong> that to efficientlyspin finer counts, combing may be required.

FABRIC QUALITYNe 30/1 yarn from each gin treatment wasknitted into single jersey fabric. <strong>The</strong>se sampleswere then subject to a pilling resistance test.MVS fabrics are generally highly resistant toabrasive damage <strong>and</strong> pill formation, <strong>and</strong>consequently retain a fresh appearance evenafter many launderings.All fabrics in this trial were rated as having no orlittle pilling.CONCLUSIONSTreatment <strong>of</strong> seed cotton before <strong>and</strong> duringginning, especially with respect to <strong>fibre</strong> moisture<strong>and</strong> drying temperatures, has significant <strong>effect</strong>son <strong>fibre</strong> quality. Dry seed cotton <strong>and</strong> hot air inthe gin lead to high <strong>short</strong> <strong>fibre</strong> content, <strong>short</strong>erstaple length, increased <strong>neps</strong> <strong>and</strong> reducedstrength. <strong>The</strong>se properties have adverse <strong>effect</strong>son both the quality <strong>of</strong> spun yarn <strong>and</strong> theefficiency with which the yarn can be spun.With MVS yarn, higher <strong>short</strong> <strong>fibre</strong> contents leadto greater <strong>fibre</strong> loss around the MVS twist zone,which translates directly into lost production forthe spinning mill.High <strong>short</strong> <strong>fibre</strong> also contributes to poorer yarntenacity, poorer yarn evenness, higher levels <strong>of</strong>imperfections, higher yarn hairiness <strong>and</strong> lowerspinning efficiency. Conversely, elevated neplevels in <strong>fibre</strong> did not translate into higher yarnimperfections, because <strong>neps</strong> are removed at thetwist insertion point during MVS spinning.In terms <strong>of</strong> grade <strong>and</strong> trash content, the cottoninvestigated in this study would normally bedescribed as a high quality growth. But for MVS(<strong>and</strong> ring) spinners the control cotton (AS) couldonly be described as being <strong>of</strong> reasonable quality.<strong>The</strong> AS treated cotton performed worst in almostall yarn quality indicators.MVS spinners require better lengthcharacteristics to achieve the desired quality intheir yarns. <strong>The</strong> results from this study showthat cotton treated with more moisture <strong>and</strong> lessheat in the gin performed better on MVS interms <strong>of</strong> yarn quality, spinning efficiency <strong>and</strong>raw material cost savings.

This study was funded by the CRDC <strong>and</strong> CSIRO Textile <strong>and</strong>Fibre Technology. Assistance was received from: <strong>The</strong>NCEA, Queensl<strong>and</strong> Cotton (Dalby Gin), Rocklea SpinningMills, Muratec Ltd, Trützschler GmbH & Co. KG <strong>and</strong>Schlafhorst GmbH.