FiberProperties Effect On Yarn Properties
Oneof the most important characteristics in the selection of yarn is thediameter of its fiber. The fiber has a significant effect on theproperties of yarn. Based on the types of fibers, yarn can becategorized as either thin or thick. The thick and thin fibers differon how they are arranged in the thread axis. At the same length,thicker fibers tend to align themselves away from the vertical axisof the yarn. The fine ones, on the other hand, are closely alignedwith the axis. This property led some group of workers to concludethat the thickness of the fiber is directly proportional to thehairiness a yarn, implying that thick fibers make the yarn hairier.
Thecompression and width of yarn are, at times, affected by the diameterof fibers (167-169). Regarding this, a relationship between the fiberdiameter and compression was established, and it was noted that theyarn`s ability to resist compression increases with an increase indiameter of fiber. Another correlation was that wiry fibers wouldresult in thicker yarn even when subjected to heavy loads due totheir ability to resist force.
Thethickness property of yarn can be adjusted by the application ofcrimp (168). In this effect, increasing the diameter of fiber willresult in a reduction of wool`s thickness. Other yarn properties thatare affected by the fiber are the linear density and irregularity. Itis evident that, at a given rate, these two properties increase withan increase in the diameter of fiber. There are theoreticalframeworks that further explain the relationship between fiberdiameter and the yarn irregularity. A correlation established bythese frameworks is that irregularity is any abnormal function of theright number of fibers in the cross-sectional area of any given yarn.To further support this phenomenon, further studies have proved, fromfirst principles that this relationship is, indeed, right. Theystated that rough fibers are likely to produce more irregular yarnsunder any conditions, whether suitable or unfavorable. Theexperimental values, as indicated by these studies are as follows
Irregularity(thickness) = (0, 9)
Irregularity(number of fibers in the cross-sectional area of yarn) = -0, 4
Itwas further noted that the diameter does not have any significanteffect on the medium range of yarn irregularity which lies betweenthirty to three hundred centimeters (186).This led to theconclusion that when the diameter of a fiber is increased, yarnbreaking strength is adversely affected. Its elongation property isalso affected, as well as the surface contact between one fiber andthe other. The effect of fiber diameter is critically analyzed whenthe yarns become finer. It is critical to evaluate the impact of thefiber since it may distort the yarn and render it useless (163). Ameaningful correlation exists between the linear density and stressresistance of yarn and the diameter of fiber. It was noted that theseproperties are inversely proportional to each other. The tensilestrength of yarn is also affected by the diameter of fiber. Studieshave shown that an increase in the diameter of fiber will negativelyaffect the regularity of yarn and thus, such properties must becritically analyzed (140).
Animportant property of yarn that is affected by the fiber diameter isthe frequency of the thick and thin portions. Exponential growth isnoted in these frequencies when the diameter increases. The lineardensity of yarn, however, is not affected by this. The existence ofthe exponential correlation is realized in other portions of the yarnas well (180, 192). The relationship, however, is more comprehensivein these areas than in the frequencies of the thin and thick placesof the yarn. The diameter of fiber has an effect on the Repco machineas well (166). This can present a serious challenge in the processingof yarns and, therefore, it is crucial to determine the rightdiameter of a fiber for any given machine to avoid damage and totalbreakdown. The faults in a yarn are said to increase when thediameter increases, while a decrease in diameter gives the yarn asuitable capability to resist abrasion (194).
CVof the Fiber Diameter
TheCV of fiber diameter has potential effects on the yarn properties.The structure of the wool is given a unique characteristic by thedistribution of the fiber. It is said that the top parts of a yarndiameter have a close similarity to that of a raw wool (38). The topsof the yarn vary depending on the intended use. To achieve thedifferent property, the CV of the fiber diameter is varied.Commercial tops can be achieved by setting the range of CV betweentwenty to twenty-six percent. The Australian flock has distinctcharacteristics of commercial tops. It can be noted that such flockshave a higher CV compared to others.The CV in the fine structuregives the yarn its roughness property. It is the determinant of theshort-term variation that is expected for yarn. The CV of the fiberdiameter also has an impact on the irregularity. It is said that theirregularity increases with an increase in CV. This effect is notmanifested to a bigger extent in the handles of a loose thread. In anexperiment, it was noted that a change in the CV did not have anysignificant effect on the weights of the components. However, whenspinning commences, the diameter can have a significant effect.Depending on the spinning technique used, the CV can negativelyaffect the nep formation. When the threads are fine, the formation ofnep is likely to grow at a faster rate. There is a range of values ofCV within which the effect on the overall efficiency of the spinningprocess is insignificant. An experimental study further proved thatthere is an effect on the effectiveness of the process when CV israised. Under normal circumstances where the value of CV is withinthe allowable range, its effect on irregularity is negligible.Another relationship was established between the change in CV of thefiber diameter and the yarn properties. It was found that varying theCV would not cause a significant shift in the structure of yarn. Thevariation in CV, however, has an impact on hairiness. A positivecorrelation between these two properties was established. On anaverage value of five microns, the effect of CV on yarn properties isnot significant.
Thelength of fiber mainly affects the quality of the threads anddetermines the type of processing technique to be used. Both theshort and long fibers are noted to have an impact on the overallquality of yarn. It was noted that rotor spinning technique ofprocessing is not significantly affected by the fiber length. Asmentioned earlier, short fibers are coarse while long fibers arefine. This implies that fine yarns are likely to be achieved by theuse of long fibers. For this reason, cotton waste is the mostsuitable raw material for many applications. The tenacity and purityof yarn are, however, affected by an increase in staple length.Longer fibers, on the other hand, yield a lower number of fiber endsat a given length of yarn. There have been variations in prices ofyarns based on the length of fiber used. A significant increase inprices was, for instance, noted between 1976 and 1977 where a largenumber of wools made from fibers with a staple length of 84mm weresold in South Africa.
Effectsof Length on Yarn Properties
Withan increase in the average length of the fiber, the worsted yarnswill appear to be improved, and the overall impact will be presentfor the shorter fibers (see fig. 16). This will depend on the yarnlinear density as well as the twisting effects. At the same time,when the fiber length is increased, it will tend to have a beneficialimpact on the irregularity of yarns in the short run, whereas, adecrease in the frequencies in the thin and thick places will causethe length of the fiber to increase. In most cases, an increment inthe length of the wool may result to an unfavorable effect on thefrequencies of the neps in yarns which may not be constant. As aresult, we will have the effects as described below:
Irregularityα (length) -0, 2
Frequenciesof thin and thick places α (length) -2
Extensionat break α (length) 0, 8, and,
Breakingstrength α (length) 0, 4
Likewise,the numbers of yarns faults and the slubs will be diminished as thelength of the wool fiber is increased however, there will only be aslight change in the yarns irregularity in both the medium and longrun. During the rotor spinning, it can be observed that the longerfibers will only produce extensible, tougher and thinner yarns thoughthe impact will be less significant for the ring threads.
CVof Fiber Length
Insome recent study, it was found that, within the ranges which the CVcovers, any major increase in fiber length will cause a small effecton the spinning performance (see Table 1). A group of workers evennoted that an optimum CV length of the fiber during spinning failedto be supported by successive works (49a, 416). We could only referto the CV of fiber length as the one that is at the top stage and notin the raw wool. The two aspects portray complete different notionsbecause, as the fiber breaks during the processing stage andespecially during the carding phase, the fiber length variations willbe increased by more than double even after the noil is removed (38).At 20%, changes mainly occur at the top phase due to the variances inthe raw wool. The remaining 80% will be because of the blending andthe fiber breakage during the stages of carding and combing. At thenormal ranges of between 35% and 55% at the top, the effects of thevariations in the CV of fiber length during the spinning process willhave an insignificant effect and may not always be steady. Theresulting effects of the CV fiber length can become more noticeablewhen the finer yarns are being spun (180,416) in which case, it couldonly depend on the particular spinning system put in place. Somestudies have also proposed that when the CV of the fiber length isincreased, it will result in an unfavorable effect on the frequenciesof the short yarn faults. As such, when CV of the length of fiber isincreased there will be an increase in the frequency of the neps inthe yarn. The blending of raw wool also differed significantly withthe staple length and hardly affected the frequency of the yarnfaults in any way (Classimat, 165). At one occurrence, it wasobserved that, when the blending raw wool differed to a larger extentin the yarn staple length, the fiber breakage during the cardingprocess and the percentage noil of the blend will be slightly higherthan the standard of the behavior of the component lots (116). When asimilar approach is applied to the average length of the fiber at thetop phase, then the effect will be slightly lower than it wasexpected and in the end, the conversion ratio will become inferior(116). There has been some powerful impact on the yarn properties, assuch valuable results were achieved during spinning of yarns andknitted fabrics (163,165). With blends incorporating different typesof fiber lengths, any resultant increase in the CV of fiber lengthwill lead to favorable outcomes.
Inpractice, the strength of the fiber is assessed subjectively orobjectively where it is taken as a measure of fiber tenderness orsoundness. Wools are often penalized if their strength falls below30% of the sound wool, as such tender wools are usually subjected toa price discount (40,571).The fiber strength is considered to servethe function of the fiber diameter, more particularly on the minimumdiameter or the cross-section. Apart from the steely wool and thebellies, there exist slight variations in the inherent strength ofthe untreated wool from the Merino breed of sheep. Additionally, thecore fiber strength is not significantly altered in tender wool inwhich case, an increase in the fiber diameter occurs along a singlefiber. Fiber strength will be reflected when fiber breakage happensduring processing (565), and it is presumed that the staple lengthand strength will provide a good prediction of the fiber length foraverage processing conditions. Sturdy wools are said to be weaker andhave low crimp than the normal wool. One employee was able todistinguish between the "tender" wool and the break. Withthe tender wools, they tend to break at any point along the staplelength whereas the "break" will only occur at only onepoint in time. The break comes into play when the fiber diameter isreduced, which is caused by the periodic changes, the nutritionvalues and other factors including day length, with the last stimulusbeing stressed on the lamb, having been caused by the climate changesor an infection. On the other hand, tenderness is caused by attacksfrom the micro- organisms and can occur in shorn fleeces if stored ina damp environment (19). An instance was where the finer fibers werereportedly (563) more variable in their cross-sectional area comparedto the coarser fibers, which could thus explain the prevailing trendsto show that fiber firmness tends to grow with an increase in averagefiber diameter. The importance of diameter remains definite as theimpact of CV of fiber diameter within normal ranges is small,whereas, the effect of the fiber length decreases as the processingstage becomes least in the final fabric. Any changes in the wools`overall mechanical properties tend to reflect the change in fiberdiameter either locally or over the whole fiber, and the former maybe an essential factor to regulate any observed differences in thewool lots, breeds, etc. It is crucial to examine the effects oflength and percentages of fibers on yarn properties. The effect ofstrength of the fibers on yarn properties must be considered duringprocessing.