Effectof diameter on Yarn Properties
Essentially,diameter is one of the most vital factors that affect the nature offibre properties and consequently contribute to the characteristicsof yarn. Specifically, how the fibres align from the yarn core (axis)determines the length of diameter in question, with coarse fibrestending to lie further away from the axis than the finer ones. Withevery increase in the diameter of fibre, there is a considerable andproportionate increase in the hairiness of the yarn. Moreover, thediameter of the fibre, as it varies (167-169), also affects thethickness and compression qualities of the yarn. Mainly, yarns tendto develop more compressive resistance as the fiber diameterincreases, an implication that coarser fibres provide higher loadresistance as much as they produce thicker yarns at higher loads.However, the impact of diameter on the thickness of yarn at low loadsis counteracted by the effect of cramp (168), with the thicknessactually reducing with an increase in the diameter of the fibre.Similarly, it is true that any increase in diameter at a constantyarn linear density triggers an increase in the short-termirregularity of the yarn, which is considered as the inverse functionof the average fibre numbers in the cross-section of the yarn.However, experimental data have indicated that this is applicablestrictly to the first application, after which coarser fibres tend toproduce more irregular yarns with constant fibre numbers in the yarncross-section. Notably, empirical studies have shown that thefollowing relationship exists for the irregularities noted above:Irregularity α (Diameter) (0,9) and Irregularity α (Number offibres in yarn cross-section)-0,4.
Conversely,fibre diameter has insignificant effect on the medium-term (30-300cm) and long-term (100m) of yarn irregularity (186). In tandem withthat, an increase in the diameter of fibre elicits a decrease in thebreaking strength of a yarn because of an increase in the short-termyarn irregularity and decrease in the fibre-to-fibre surface contact.Notably, the effect of the diameter of fibre on yarn strength isbecoming more decisive as finer yarns are spun (163). Additionally,at a constant yarn density and twist, the breaking twist isindirectly proportional to the average diameter of the fibre.Moreover, an increase in the fibre diameter also impacts the tensileand irregularity of rotor yarn but adversely (140). Furthermore, thefrequencies of thick and thin areas in a yarn have been shown toincrease exponentially following an increase in the diameter of fibreat a constant linear density of yearn (see fig. 6). In relation tothat, the approximations already tasted show the followingrelationship: Frequency of thin places α (Diameter) and Frequenciesof thick places α (Diameter). In fact, more detailed empiricalrelationships (180, 192) show that an increase in the diameter of thefibre has an adverse result on the properties of a Repco machine’sRWCS yarns span (166). In general terms, an increase in the diameterof fibre increases the yarn faults’ frequency (112), especially forthe faults and neps that are longer shorter neps and faults exhibitantonymous trends (147, 164). Again, an increase in the diameter offibre is proven to improve yarn abrasion resistance (194) as much asit also increases the stiffness (196) and torque (196) of yarn.
Thedistribution of the fibre in the tops closely mimics that in the rawwool (38). For example, in commercial tops, the variation of the CVof the fibre diameter ranges between 20-26%, and increases with theincreasing mean fibre diameter (56, 290-292). Mainly, the fibrediameter’s CV in commercial tops is larger than within Australianflocks as attributed to the trade practice which selectively mixeswool lots from varied sources (135, 293). However, the disparity inthe CV of fibre diameter tends to impose negligible effect on theloose wool handle (74, 76). It has been mapped (7) that, with theexception of spinning performance, blends of wool differing by up to5 µm in the diameter created during processing, as predicted fromthe component lots’ weighted means, the associated increase in CVof diameter has little effect. On the other hand, the occurrence offine fibres in a mix induces a considerable increase in the formationof nep (101 b). Similarly, within practical ranges, the result of theshifts in the CV diameter on spinning performance is generally petite(7,14a, 111,123, 132, 294, 295) but momentous, with every increase inthe CV diameter triggering a deterioration in spinning performance(7, 49a, 111, 123) (See Fig. 12 and Table I). Arguably, the effect ofshifts in CV of diameter on yarn irregularity, within normal ranges,is so minute both theoretically (184, 297) and practically (2,177,162,178-180,288a, 294,295,297,298) that it can be disregarded formost purposes. Often, the impact of normal variations in the fibrediameter’s CV on the physical properties of the yarn as small (2,111, 162, 177-180,188,191,288b, 294,295,298) to warrant neglect formost practical activities, although it could prove incisive forlimiting counts. The small impact of variations in the CV of fibrediameter on the properties of yarn was validated in the studiesinvolving the mixing of wools conflicting by up to 5 µm in theaverage fibre diameter, with the outcome of mean fibre diameter (2)predominating.
Lengthis perhaps the most influential factor, only second to diameter, ininfluencing the quality of wool (33, 38). However, it has a smalloutcome on the price unless the context points to a change in theprocessing system (187). Hence, at the top stage a price discrepancyof only about 2-3% per 10 mm hauter was noted in 1973 (299). Duringthe 1976/77 season 12 months wool featuring 84 mm staple length, theprice was only slightly higher at 2-3% compared to that of 9/11 monthwool featuring 70 mm staple length (300) these scenarios were notedfor wools ranging from 19,5 to 24,5 µm sold in South Africa. Whenreferring to length, it is imperative to pinpoint how and at whatstage it is measured since, unlike diameter, the processing actionslike carding modifies the characteristics of fibre length.
Effectof length on Yarn Properties
Usually,an increase in the mean fibre length improves the tensile strength ofworsted yarn and with the effect more pronounced for short fibres(Fig. 16). That effect is highly dependent on factors such as thelinear density and twist of yarn. Furthermore, an increase in themean length of fibre has some benefits on the short-term yarnirregularity as well as the frequencies of thin and thick places theeffect decreases with every increase in the fibre length. However, anincrease in the mean fibre length posits an adverse impact on thefrequency of neps although the effect is inconsistent in yarn (117,180)179 177 165 164). Nonetheless, the following approximations occurwithin normal ranges: Breaking strength α (Length) 0,4 Extension atbreak α (Length) 0,8 Irregularity α (Length)-0,2 and Thin andThick Place frequency α (Length) -2. An increase in the length offibre also considerably reduces the number of yarn faults and slubsas much as it has little impact on medium-term and long-term yarnirregularity. Conversely, an increase in the mean fibre length from30mm to 50mm, for short-spinning, increases yarn irregularity as wellas the frequencies of the thick places and neps. In fact, longerfibres generate more flexible, leaner, and extensible yarns in rotorspinning, but with the results being smaller than for ring yarns.Similarly, an increase in fibre length results in the reduction ofyarn hairiness as much as it enhances abrasion resistance. Besides,fibre length affects the thickness and compression qualities of yarn,with fibres which are shorter producing thicker, compressible yarns.
Themain aspect that scientists consider regarding the fibre length CV isthe one at the top as opposed to the raw wool because the twoelements are dissimilar due to the effects of fibre breakages knownas carding. In other words, the breakage of fibre especially in thetime of processing leads to the drastic increase of the lengthvariance and in some case it may be more than twice the original oneeven if the noil got removed. There are two facets that lead tochanges in the length of a fibre which are raw wool variation as wellas fibre breakages as a result of carding and combing and in suchscenario, the first one causes 20% of the length variation while thesecond aspect leads to the remaining 80%.
Scholarssuggests that the overall visualization of diverse analysis ofdifference in fibre length CV due to the performance in spinning aswell as fabric and yarn characteristics shows that there is smalleffect which is not consistent. Such effect is only available if thestandard practical range of approximately 35% to 55% in the upperpart is taken into consideration. However, some researchers claimedthat they attained an optimum fibre length CV through spinning eventhough there are no subsequent activities that support such isolatedcase. Besides, a recent extensive study showed that the increase infibre length CV had limited fundamental effects on the spinningperformance especially on the ranges of CV that they covered. Theresearch, therefore, suggested that the effects on the CV of thelength of the fibre may arise due to the spinning of the fine yardand vary according to the system utilized for spinning which makesthe length a little bit pronounced.
Furthermore,it worth noting that the frequency yarn neps is the main facet thatmost scholars associate with the rise of the length of fibre CV dueto its effects on the yarn short faults. Precisely, recent studiesrevealed that the length of the fibre CV interferes with thefrequency of the yarn short faults at an adverse rate except in ascenario of raw wool (180). The analysis of different researchesrevealed that the raw wool of diverse staple length had no adverseeffects on the frequencies of the yarn faults in cases the scholarsblended them. However, one analysis indicated that wools of highlydissimilar staple lengths experienced fibre breakages during blendingand the blend’s percentage noil was a little bit greater than theproposed behavior of the constituent lots while the mean length ofthe fibre of the upper part was slightly smaller than the proposedbehavior.
Onthe other hand, there was an evidence on the fundamental effect ofspinning performance while the yarn and fabrics the blends usingdiverse lengths of fibres demonstrated the predicted performance fromthe behavior of the constituents where increase in the fibre lengthonly had effects on yarn neps (163, 165).
Itis notable that tender and break are the main concept that lead tothe breakages of fibre especially in the times of processing eventhough tender wool can tear at any point while break only occur at aspecified weak point (19). Precisely, a break result from reductionin the length of the diameter which is led by the seasonal dynamicsas well as sustenance causes such as length of the day but theextraordinary stimulus is sheep and lambing stress which comes aboutdue to climate or disease. On the other hand, tenderness occurs dueto infestation by the micro-organisms and that takes place in theshorn fleeces if people keep them in a damp condition.
Ina different case, fibre length is influence by the diameter of suchwool particularly the minimum diameter or cross section with anexception of steel wool that is deficient of copper and bellies whichhave suffered from bacterial damages. Besides, there is limitedvariation in the intrinsic length of wools that has not undergonetreatment within the breed of a merino sheep. In the cases of tenderwool where there is tremendous dynamics in the diameter of a singlefibre, there is still minimal alteration on the tenacity of the wool(77). Furthermore, the dynamics in the wool mechanicalcharacteristics reveals the changes in the diameter of the fibresmostly in the local or entire fiber but the local dissimilarities isa fundamental factor responsible for the noticeable differencesbetween the wool lots and the breeds. For instance, researchers arguethat fine fibres have more variable cross-sectional diameterscompared to coarse fibres that is that main reason why they tenacityof the fibres increase with the rise in the mean diameter (563).
Thefibre strength gets noticed in the fibre breakages in the cases ofprocessing therefore, the combination of the staple length andstrength offer a fundamental prediction regarding the overageprocessing situations of the fibres at the upper part. Wools thatare steely have feebler and inferior crimps compared to the normalones thus they have adverse processing conditions and staple strengthpractically examines the tenderness and soundness of the subject orobject wool (565). In most scenarios the tender wool experienceprice discount because buyers are fond of penalizing the wool if itsstrength is below 30% of the product proven to be sound. However,the concept of the soundness of fibre gets reflected as a result ofthe diversity in breakages of the item when subjected to combing andcarding as reported in the in the value of the South African wool dueto staple strength (315). It is evident that greater staple strengthleads to less breakage when a fibre is taken through combing, cardingand spinning thus resulting into tops that are straighter and havingan advanced tear. According to recent studies of staple strength,scholars proposed that yarn and fabric strengths could beproportional to the strength of a fibre and such case require anexperimental confirmation. The technical fundamentality of fiberdiameter are still intact, yet the interference in the CV diameter islittle at the standard limit with exception from spinning near theboundaries. Besides, the importance of the lengths reduces as theprocesses progress towards the final fabric while the CV of the fibrelength and short fibre percentages remain at the constant mean.Furthermore, the normal ranges get faced in practical works when anindividual utilizes drafting techniques that require double apronsystem (628). However, the mentioned elements indicate the level offrequencies in places that are short and thick as well as nep in theyard even though they reflect limited effects in the fabric.