Wool and Cashmere Apparel Fibers

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Wooland Cashmere Apparel Fibers

Wooland Cashmere Apparel Fibers

2.2Woodland cashmere apparel fibers

Someof the key mammalian fibers that are commonly used in the moderntextile factories include cashmere, wool, and alpaca. However, woolis the most important type of animal fiber out of the 20 options thatare available since it has more commercial benefits. It is estimatedthat about 552 million kg ($ 1) of wool are produced every year.Alpaca and cashmere are considered as luxury types of fiber. Thisclassification is attributed to their price, softness, exclusivity,image, and rarity ($ 2, $ 3, $ 5). Statistics show that about 5million ($ 6, $ 7) and 15-20 million ($8, $ 9) kilos of alpaca andcashmere are produced each year, respectively. The global consumptionof the fiber that is classified as man-made increased exponentiallyup to 50 million tons from the year 2008 when it started reducinggradually. The decline has been attributed to the financial crisisthat affected the world economy in that year.

2.3.1Wool

Thetype of hair that is obtained from domestic sheep is known as wool($11,12, 13). The world has over 500 different breeds or varieties ofsheep, which explains the fact that wool has varying characteristics.The wool that is obtained from merino has unique features, and it isconsidered to be soft, high quality, and fine. These characteristicsmake merino wool a suitable option for apparel production ($ 14). Itis estimated that merino’s fiber is about 50-125 mm in terms oflength. However, differences in the size of the length are influencedby different factors, including the environmental conditions andgenetic composition of the sheep ($ 15). The diameter of the fiber isestimated to range between 10 μm and 25 μm, but the coarseness ofthe wool is approximately 75 μm ($ 16, 17). These features makemerino wool the best choice for upholstery and production of carpets.Studies have shown that an average merino sheep can produce about 6kg of greasy wool ($ 18).

Woolhas been the most common and significant type of apparel in the worldfor many, but it is being replaced by alternative types of fiber(such as synthetic thread and cotton) progressively. The world hasbeen moving towards an increase in the production of synthetic fiberfor different reasons. For example, the desire to contain the cost ofproduction makes the stakeholders in the textile believe thatreliance on the fiber that is produced in the industries can helpthem make apparels at a lower cost. Apart from the economic factors,the demand for meet has lowered the population of sheep, which hasmade the production of synthetic fiber a viable option. It isestimated that its share of the global apparel market has fallen to 2% ($ 19). Wool has been one of the key sources of foreign currencyfor some countries (such as Australia) for the last 120 years ($20).However, the wool industry crashed in 1991, which resulted in asignificant decrease in its value as well as its contribution to theAustralian economy. Australia has remained the world’s largestproducer of sheep wool globally, in spite of the significant decreasein the value of the fiber in the last three decades ($ 21). Datashows that about 260 million kg of wool was produced by Australianfarmers in 2009, which contributed about $ 2.0 billion in thecountry’s economy ($ 22). Therefore, Australia has managed tomaintain its position as the global leader in the production of woolfiber.

3.2.3Cashmere

Cashmererefers to a fine inner-coat that is obtained from goats (such asCaprahircusLaniger)that are domesticated in many parts of the world ($ 23). It isconsidered as a luxurious and one of the softest types of fibers thatare obtained from animals ($ 24). The high level of luxurious appealof the clothes that are made of cashmere is attributed to itssoftness ($ 25). Afghanistan, China, Tibet, and Mongolia are themajor producers of cashmere. However, there are some countries (suchas New Zealand, Iran, and Central Asia) that produce it in smallquantities ($ 26). China produces the best quality of cashmerecompared to other nations. The level of quality of the fiber isattributed to many factors, including the environmental conditionsand the suitability of the farming practices. The type of fiber thatis produced by the Chinese farmers has a narrow diameter of about14-16 μm ($27). Cashmere is usually harvested during winter, wherefarmers comb or collect the fallen fiber from the floor ($ 28). Thepossibility of collecting the fiber from the floor makes harvestingquit easy. However, it presents a unique challenge because farmersare expected keep the sheep houses in order to protect fiber that hasbeen deposited from dirt and other types of contaminant.

Practicesare quite different in Australia where the fleece is shorn during themidwinter period and the coarse hair removed through the process ofde-haring ($ 29). The relationship between the time and the practiceof harvesting the hair suggests that the production of fiber isdependent on the environmental conditions and seasons. According toWang, Singh, and Wang (2008b) the cashmere that is produced by theAustralian farmers has about 70 % coarse hairs. Under normalcircumstances, cashmere that is obtained from goat weighs about0.06-1 kg. The length of cashmere varies between 35 mm and 80 mm,while its fitness is about 14 to 17 μm ($ 31). However, cashmerethat is obtained from Iran has a diameter of about 17 μm to 20 μm($ 32). Cashmere is considered as an expensive and rare type of fiberwith a limited supply and a high cost of processing ($ 33). It isquite difficult to substitute cashmere, but researchers have focusedon the development of techniques for the identification of othertypes of fiber ($ 34). Therefore, the uniqueness of cashmere givesits some economic value compared to other types of fiber, includingwool. In addition, the limited supply creates an opportunity for themarket forces of supply and demand to play the role of increasing theprice of cashmere. Wool is readily available and easy to process, butits price is low compared to cashmere.

2.3.4Processing of cashmere and wool

Theprocess of converting the raw wool into finished fabric is quitecomplex. This process has been refined over the years to the currentprocedures that are used in the textile industry. Currently, scholarshave provided a large volume of information about the processing ofwool, but the techniques used in the conversion of cashmere and otherrare fibers are confidential ($ 35). The rare fibers are processed bya few companies, which explain the reason for the availability oflimited information about the techniques used to process it. Machinesused to process wool can also be applied in the conversion of othertypes of fiber to finished products, but a few adjustments shouldmade in order to enhance efficiency ($ 36). The need to make someadjustment in when processing the rare fibers is attributed to thefact that they have different properties from wool. The conversion offiber into finished yarns involves a series of complex processes. Theinitial process is the purification, and it is accomplished throughthe removal of dirt, grease, soluble proteins, and vegetable matter($ 37). Some types of fleece are dusty and may require the processorsto dust them before souring ($ 38). Wool that is collected from thefloor is one of the examples of finer that may contain dirt. However,some fiber might catch dirt and other types of contaminant during theprocess of harvesting.

Fibersare then dried, blended, lubricated, and moistened in order tominimize problems that are associated with the breakage of the fiberand static electricity in the successive mechanical processes. Somefibers (such as alpaca and cashmere) contain guardian hair, whichcreates the need to de-hair them. The process of de-haring involvesthe removal of coarse hair and its separation from the valuable aswell finer fibers that are yielded by the secondary follicles ($ 39).Processors can use three types of schemes (including the worsted,woolen, and the cotton system) to convert the scoured staples intothe finished yarn that is then used in the production of apparel ($40). Figures 2-3, 2-4, and 2-5 shows the summary of the operationsused in processing the fiber via the three types of systems. Thethree types of processing systems are differentiated by the level ofalignment and short fibers in the final yarn ($ 41). A decision onthe type of system that should be applied in the process ofconverting the fiber into a yarn should be informed by the propertiesof the raw material. For example, process should take account of thekey features (such as the softness, length, and hairiness of thefiber before selecting the type of system that should be applied.

Processorsuse the woolen systems to complete the randomness that is associatedwith the orientation of fibers that form the yarn. The system formsthe shortest route for processing fibers that are classified on thebasis of their softness, bulkiness, and hairiness ($ 42). Theluxurious fibers (including the vicuna, alpaca, and cashmere) arespun using the woolen system ($ 43). However, different forms offiber waste (such as noils) may also be processed using the woolensystem ($ 44). The system helps the processors exploit the softnessof the raw fiber, which results in the production of yarns witheasily compressed surface fibers ($ 45). In other words, the type ofthe system that the processors decide to use determined their abilityto take advantage of the features of the fiber in producing qualityand marketable yarn and apparel. According to McGregor (2001) about90 % of all de-haired cashmere is converted using the woolen system.Processors use the worsted system to align the fiber in a parallelway before spinning it, which is accomplished through a series ofsteps. In most cases, fibers that have a length of about 40-200 mmare processed using the worsted system.

Oneof the key steps that are observed when using the worsted system isthe combination of operations that involve the removal of neps,vegetable matter, and short fibers. The emphasis on the need toremove the dirt is associated with the high probability of harvestingcashmere that is contaminated by solid matter compared to other typesof fiber. The remaining fiber is arranged and put into a parallelformation. This system allows processors to spin finer, uniform,stronger, and less hairy yarns ($ 46). However, worsted system mayalso be applied in processes that involve the conversion of fiberwith more than 40 mm ($ 47). This provision has enabled Australianprocessors to convert about 80 % of the fiber using the worstedsystem. Cashmere with longer length and alpaca can also be processedusing the same system ($ 48, 49). Studies have also shown thatcashmere and their blends are also converted using the worsted systemin Australia ($ 50).

Mostof the cotton wool (about 60 %) is converted using the ring spinningsystem ($ 51). A different technique is applied when processing woolbecause the two types of fiber have different properties that forceprocessors to use dissimilar processes. The fiber is expected to beat least 50 mm for it to be processed using the ring spinning system.Processors are required to add more fiber in the yarn cross sectiondue to the short length of the fiber used in the spun yarns. It isrecommended that processors should put at least 80 fibers in order tospin a quality yarn using the cotton system ($ 52). The length of thewool is reduced by cutting or stretch breaking since it is quite longcompared to cotton. The reduction in the length is done when theprocessor intends to apply the cotton system ($ 53). Many processorsprefer the stretch-breaking technique since it minimizes thevariability of the distribution of the fiber. The process of cutting,on the other hand, produces short fibers without affecting thevariability ($ 54). In overall, the length of the fiber is one ofthe key factors that the stakeholders in the textile sector use toselect the most appropriate type of processing technique.

Processorsblend short wool fiber with about 20-25 % cotton in order to minimizeproblems during lap production. However, about 100 % of the wool isprocessed using the cotton system ($ 55). A study conducted byMcGregor (2001) indicated that it is possible to spin yarns with morethan 36 tex from cotton and cashmere noil. McGregor was unable tospin a fiber that was 100 % made up of cashmere. Madeley (1994)managed to spin a small quantity of wool obtained from lamb andcashmere on the Platt’s spinning plant. Madeley used the slip draftapproach. McGregor (2001), on the other hand, reported an error rateof about 38 %. However, the researchers did not take account of otherfeatures of the yarn. This consideration made it impossible to tellwhether the yarn that they produced was sufficient to compare fabricsor not.

2.3.5Growth, physical, and chemical structure of cashmere and wool fiber

Eachmammal has a unique type of hair ($ 56). The development of uniquetypes of hair for each mammal occurred during the process oftransition from Triassic to Jurassic periods, which took place in thepast 200 million years ($ 57). Some of the key functions of hairinclude the protection of the animal from environmental conditionsthat are harsh, provision of the element of camouflage, prevention ofthe loss of water, and the regulation of the level of temperature ($58). Scientists have identified that all mammalian hair has a similarstructure, chemistry, and morphology ($ 59). All these featuresappear before the hair can emerge from the animal’s skin. Thebasics structure of the hair is similar, but the general features maydiffer from one type of animal to another.

2.3.5.1Growth of the animal’s fiber

Thegrowth of the mammalian hair starts from the usual hair folliclesthat are located in the animal’s skin. The hair takes about oneweek to pass through the animal’s follicle ($ 60). Factors thatdetermine its chemical as well as the physical features developsbefore it can start emerging from the follicle. Fibers that are fullygrown are shed depending on the cycle of the hair. The term cyclerefers to the process that involves the growth of hair from the timeit starts developing in the follicle until when it is shed off by theanimals. The hair becomes loose and detaches from the skin of theanimal at the end of the growth cycle. A standard hair cycle iscomprised of three steps. The first step is a period in which activegrowth (anagen) of the cell occurs. During the first phase, the cellsdifferentiate depending on the type of physical as well as chemicalfeatures that are expected to appear on the hair once it emerges fromthe follicle. The second phase involves the duration in which cellgrowth is halted and follicles begin to shorten. The shortening ofthe follicle is a process that indicates the preparation of the hairto emerge. This process makes it easier for the hair to appear abovethe skill of the animal. The last phase is referred to as the restingstage (telogen). This stage takes place when exogen is completed anda new phase of anagen begins ($ 61).

Theactivity that occurs in individual follicles can undergo changes atany time during the lifetime of a given animal ($ 62). The cavitiesfrom where the growth of the hair starts can be classified into twogroups. These groups include the primary and secondary follicles.Follicles are differentiated on the basis of their respectiveaccessory structure. The morphology of the follicle is characterizedby subiferous gland that is responsible for secretion of suint,arrector pili muscle, and sebaceous gland coating the animal’sfiber with wax prior to its emergence from the beneath the skin ($63). The hair is coated with wax before its emergence from thefollicle for different reasons. For example, a hair that is coveredis has a less friction and it is repellent to water. The cover alsoprotects the skin of the animal from water and dirt. Therefore, waxplays the protective role in the process of hair growth.

Primaryfollicles have the capacity to yield long coarse outer-coat and thethree accessory structures. There primary follicle facilitates thedevelopment of the outer part of the fiber or the hair. Secondaryfollicles, on the other hand, are associated with the sebaceousgland. They produce inner coat fibers with finer diameter ($ 64).Secondary follicles carry out the function of developing the interiorcomponents of the hair. Producers are interested in the number offollicles because they determine the level of softness and thefineness of the fiber (Galbraith, 2010). Apart from nurturing thefiber, follicles determine its quality and the physical as well asthe chemical features. The level of quality and other features dependon the number of follicles that facilitate the growth of a givenpiece of hair. Merino strain is yielded by two follicles and it isconsidered as a single-coated fiber, which makes it indistinguishable($ 65). The average length of merino’s anagen cycle isapproximately eight years (Panaretto, 1979). Although the durationthat the fiber takes to grow sounds to be long, different pieces ofhair mature and are shed off in different times. The follicle cyclesare independent of each other (William 1991). Alpaca is mostly singlecoated, but there are instances when coarse fibers appear ($ 66).Alpaca has a lower density (17-20 follicles per mm2)compared to wool ($ 67).

Cashmeregoats produce double-coated follicles. Their primary follicles yieldan outer coat that is known as guard hair. The secondary ones producean inner coat that is referred to as the cashmere ($ 68). Therefore,the two categories of follicles play different functions. The guardhairs are usually coarse and they have a diameter of about 40-200 μm70 μm (Teasdale, 1985). The cashmere that is produced in Australiahas a density of approximately 23 follicles per mm2 ($ 69). Thephysical as well as the physical features of the fiber may differwith the geographical location. Synchronization of the follicleactivity results in molt (Galbraith, 2010). The quantity of suint andgrease that is present varies depending on the type of follicle andthe species of the sheep ($ 70). Therefore, apart from theenvironment and geographical location from where the farmer lives,the variety of the sheep may also determine the quality and differentfeatures of the hair. Cashmere has a grease content of about 4.5 % ($70) while alpaca has approximately 5 % (McGregor, 2003). The level ofperceived softness of the fiber is determined by the grease content.

2.3.5.2Animalfibers’ chemical structure

Alpaca,wool, and cashmere are comprised of a protein referred to as keratin.This type of protein is found in other tissues, including horns,feathers, hooves, and epidermis ($ 73). There exists beta and alphakeratin, but fiber is always made of the α-content($ 74). Although fiber is made up of different types of molecules,proteins are the major building blocks. The amount of keratin inclean wool is about 82 %, while other types of protein andnon-protein content make up about 3 % and 1 %, respectively(Christoe, 1998). Non-covalent and covalent bonds play a criticalrole in stabilizing proteins that form the cuticle. Some of the keyinteractions include disulphide and strong covalent bonds thatcross-link different chains of the peptide ($ 75). The strength ofthe bond varies depending on the type of molecules and the proportionof proteins in the fiber. The breakdown of the keratin fibers resultsin the production of about 18 amino acids ($ 76). The breakdown ofamino acids takes place through the ordinary metabolic processes. Thequantity of amino acids varies depending on the type of breed and thegenetic composition of the sheep ($ 77). In overall, the specificcharacteristics that players in the textile industry look for whenselecting the type of fiber that they should buy are determined bydifferent factors, including the variety of the animals, the numberof follicles involved in the development of each piece of hair,geographical area, and the environmental conditions in which theanimals resides.

Tuckeretal(1988) identified that cashmere and merino wools that are produced inAustralia could not be differentiated on the basis of the quantity ofamino acids. McGregor and Tucker (2010) found out some differences inthe composition of amino acids of guard and cashmere fibers. However,there were no differences in terms of the Cystine contents. Cruthersetal.(2010) identified that alpaca has cystine content that is less thanthe amount that is found in wool ($ 78). Similarly, low crimp woolhas less cystine content compared to a high crimp type ($ 79). Typesof lipids that are found in wool include fatty acids (25 %), sterols(40 %), and polar lipids, 30 % (Rivett, 1991). However, the contentof lipid varies depending on the type of fiber (Logan, 1989). Therenowned softness of cashmere is attributed to the fatty acid content($ 80). Although all fibers have similar types of proteins, theircharacteristics differ depending on the proportion of amino acid inmolecules that act as their building blocks.

2.3.6Thephysical structure of hair fibers of the mammals

Corticalcuticle cells are the major components of the hair fiber. These cellsare accumulated through the process of cell membrane complex ($ 81).Figure 2-6 shows different types of cells that form the wool fiber.The variants shown in the schematic diagram were derived from fibersof other specialties, including alpaca and cashmere (Smith, 1988).Fibers with a coarse diameter have less cuticle-to-cortex ratiocompared to the fine diameter fibers ($ 82).

2.3.6.1Corticalcells

About90 % of the fiber is made of cortex that determines their mechanicalfeatures ($ 83). Cortical cells are made up of macrofibrils.Macrofibrils are made up of water impermeable and crystallineintermediate filaments. The filaments are embedded in the crosslinked protein matrix ($ 84). The basic mechanical unit of wool fiberis called intermediate filament. The filament increases theelasticity, flexibility, and resilience of the wool fiber (&amp 85).There are three types of cortical cells that are identified on thebasis of packaging density of individual intermediate filaments.These filaments include orthocortical cells, mesocortical, andparacortical ($ 86). All these types of filament have differentfeatures that help in differentiating fibers that are harvested fromvarious animals. The types of fibers that have a high content oforthocortical are mechanically weaker since their filaments arepoorly organized and they have a lower content of sulfur ($ 87). Thisweakness suggests that cortical cells play the function ofstrengthening the fiber. Merino wool that is fine and high crimp hasa bilateral arrangement. This wool has a paracortex that is found onthe inside of their crimp. All fibers have cortical cells, but theexistence of different types of filament introduces features that canbe used to distinguish between hairs that are harvested fromdifferent mammals.

Cortexcells are organized as concentric cylinders in Lincoln wool and theircore is made up of orthocortical cells ($ 88). The crimp of fine woolis attributed to the bilateral arrangement of the cortical cells ($89). Hynd etal.(2009) identified that the bilateral arrangement is an associativefactor and not the underlying cause of the crimp. Therefore, thecrimp nature of the wool could be attributed to keratinisation rateand mitotic asymmetry. Suri alpaca has paracortical cells only.Huacaya alpaca, on the other hand, has bilateral ortho-para types ofcells. The felting luster mutant produced by merino and the Mongolianhuman hair is comprised of the paracortical cells only (Li etal.,2009 and Shim, 2003). The mohair is made up of orthocortical cells,but there are some differentiated para/ortho fibers ($ 91, 92).Tester used magnification transmission to identify that cashmerefibers have mesocortical and orthocortical cells ($ 93). Brandy andWang (2005) managed to extract cells from ordinary cashmere as wellas the wool fibers, but they failed to establish the differencebetween cells of the same diameter.

2.3.6.2 Cuticlecells

Thesecells are located on the outermost part of the fiber. Cuticle cellsmake up about 10 % of the total mass of the fair fiber and they areamorphous in structure (E$ 94). Overlapping along the layers of thefiber yields the ratchet-like profile ($ 95). The overlapping alsogenerates the productive barrier that is located between theenvironment and the fiber’s cortex ($ 96). The scale edges aredirected towards the end of the fiber, which facilitates the processof anchoring the fiber to the skin. It also expels foreign matter andenhances resistance to the movement in the tip-to-root direction ($97). The shoulder scale edges are embossed when the fiber comes intocontact with the inner sheath of the root. This process occurs inapproximately 25 % of the cuticle cells of the merino fibers ($ 98).Cuticle cells have about three layers, including exocuticle,endocuticle, and epicuticle ($ 99).

Exocuticlehas strong disulphide bonding, which is attributed to a high contentof cystine. The bond determined the bending features of the fiber ($100). Epicuticle is made up of 18-methyleicosanoic acid lipid layerand proteins. Thioester bond links the lipid to proteins ($ 101). Thehydrophobic nature of the fiber is attributed to the lipid layer ($102). The surface lipid develops in conjunction with different typesof proteins. The concentration of the lipid layers differs dependingon the type of the environment (Huson, 2008). Endocuticle isconsidered as the weakest section of the cuticle. The intercellularand endocuticle attach the cells of the cuticle to the fiber ($ 103,104). The surface features of the cuticle are the key determinants ofthe level of friction, softness, physical processes, and the chemicalreactions that occur in the fiber ($ 105). The function of theexternal lipid is to minimize friction ($ 106). The production ofhydrophilic can be enhanced by removing the external lipid layer.This removal also enhances the friction coefficient, which hardensthe handle ($ 107). Therefore, cuticle cells are mainly involved thedevelopment of the outer parts of the follicle. Consequently, thephysical features (including the texture) of the hair is determinedby the cuticle cells.

2.3.6.3Culturepatterns

Thetopographical characteristics (including the height, cuticledistribution, scale shape, and frequency) and presence of the medullaare unique in the fiber that is produced by different mammals ($108). Figure 2-8 shows the pattern of cuticle that is found in merinosheep. The biochemical patterns of the cells determine the shape ofthe cuticle (Chernova, 2002). Deformation of the cell occurs duringthe process of keratinisation and differentiation of the follicle ($109). The cuticle is estimated to be one cell thick in cashmere andwool, which is about 16-20 μm($ 110). Human hair, on the other hand, has about 6-10 layers ofcells of the cuticle (Swift 1997). Alpaca has about five layers ofcuticle cells (Fan, 2008). It is estimated that the goat hair hasapproximately 10 layers of cuticle cells that surround the fiber’scortex ($ 111). The cuticle is considered to be slightly thickercompared to the paracortical side of the wool’s orthocortical side($ 112). The interval of scales changes along the specific length ofeach piece of fiber. Finer fibers have been confirmed to have scalesthat are widely spaced ($ 113). The frequency of the scales found inwool is estimated to be 6-12 scales for every 100 μm alpaca has afrequency of 10-11 and cashmere has a frequency of 6-8 ($ 114, 115,116).

Thescale height is the major factor that is used to distinguish betweenwool and specialty fibers, which are accomplished using the scanningelectronic microscope ($ 117). Processors use the DeutschesWollforschungsinstitut Aachen to conduct a quantitative analysis ofblends of fiber ($ 118). Specialty fibers and wool have a scaleheight of 0.4 μm and 0.7-1 μm, respectively ($ 119). SEM is atechnique that is used to mount fibers vertically, with the objectiveof enhancing the scale edges and facilitate an objective measurementof their sequence. The SEM technique reveals the degree of theoverlap of scales of cuticle with a higher level of clarity. Thewidth, length, and the height of cuticles can differ from one type offiber to another, but the dimensions of the fiber is not associatedwith the softness of the fiber (Whiteley, 1963 and Sumner, 2009). Thefelt-ball diameter and the fiber handles are negatively associated(Kenyon, Wickham, and Blair, 1999). In addition, the felt-ball mayalso be used as an indicator of the specific height of the scale ofthe wool fiber (Ladyman, Greeff, and Schlink, 2004).

TheSEM strategy is considered as a standard method for assessing thetopography of the keratin that forms the surface of the fiber ($120). However, the experience as well as the skills of individualoperators determines the accuracy of the SEM technique (Poletti,2003). The SPM technique, on the other hand, is used to assess hairfiber and wool. The SPM is considered as a non-invasive approach thatcan be applied without the need to prepare the samples (Poletti,2003). Apart from the natural features of the fiber, the techniqueused to process it determines the quality of the final yarn as wellas the apparel.

2.3.The importance of the length, diameter, and length of the fiber

Thedurability and processing performance are influenced by the physicalfeatures of wool ($ 122, 123). Owners of textile businesses preferwool that can help them reduce the cost of processing and enhance theprofitability of their businesses. This is quite challenging, giventhat the quality of wool is influenced by different factors,including the genetic composition of the sheep, management practices,and the environment ($ 124, 125). The collapsing of the reserve pricein Australia has been associated with an increase in competition thatemanates from fiber that is artificially processed and a decline inthe economic value of wool (Harle, 2007) ($ 126, 127). The expansionof the market has also been limited (Swan, 2010). Some processorshave been affected by the rise in the cost of production (Rowe,2010). The production of wool in Australian has reduced and farmersare no longer interested in dual-purpose farming ($ 128, 129).Farmers in Australia are able to increase the quality of wool as wellas meat through heterosis that occurs in the F 1 prime lambs ($ 130,131, 132). Some of the key features of the wool include the diametercoefficient, diameter, curvature, staple length, clean fleece yield,fleece yield, and spinning fineness (133). According to Mortimer etal.,(2010) all of the aforementioned features of the wool make asignificant contribution towards the overall value of the fiber ($134).

2.3.1The effect of fiber diameter on properties of the yarn

Diameteris one of the key features that vary along the length and from onepiece of the fiber to another one. Initial fiber that grows on thesheep is considered to be softer than the one that develops on an oldanimal (Warner, 1995). The fiber that grows on an old animal isinfluenced by different factors (such as the nutrition, climate,lactation, pregnancy, age, and health of the animal), which explainsthe existence of wool with different diameters ($ 135, 136). TheSingle Fiber Analysis is the major technique that is applied in themeasurement of variations in diameter along the fiber’s length ($137, 138). According to Hansford, 1994) the process of shearingaffects the diameter profile of the fiber. The description of thediameter of the fiber that takes into account variations in terms ofcoefficient of fiber diameter is made in the using the concept of“effective fitness” (Behrendt, 1996).

Thediameter of keratin fibers (such as wool) is taken in conditionedatmosphere because they tend to swell when exposed to hightemperatures and moisture ($ 139, 140). Processors use a relativehumidity of about 65 % and a temperature of 20 degrees to test thewool. The ultimate market value of the wool is highly influenced bydiameter of individual pieces of fiber ($ 141). This influence hasbeen observed in about 70-80 % changes in prices of the wool that isproduced in Australia ($ 142). Diameter determines the level ofperformance during the processing stage and the quality of the finalproduct ($ 143). Fine fiber is referred because it facilitates theproduction of smooth and softer handle ($ 144). In addition, thesoftness of the wool has been associated with the diameter of itsfibers ($ 145). About 66-85 % of the total score of the handle isdetermined by the fiber diameter ($ 146). Moreover, the value ofsummer suits and the stiffness of the fabric are influenced by thediameter (Hunter, 1982). The fact that the fiber can still beaffected by temperature and water, even after harvesting imply thatthe environmental conditions and climate determine its growth and theoverall quality.

DeBoos (2002) also identified that the smoothness and softness of thefiber are influenced by diameter. The increase in the fiber diameteris positively associated with the shear as well as the bendingrigidity and compression energy ($ 147). Tension rigidity changeswith the radius of the fiber up to the fourth power. This changemeans that the diameter can determine all mechanical features(Warner, 1995). The diameter has also been shown to affect thefiber’s tensile behavior (Warner, 1995). It also affects thecomfort of the skin in a significant way ($ 148). The proportion offiber ends that are more than 32 μm are associated with prickle thatoccurs on the skin of the animal ($ 149). The endings of the coarsefiber do not bend easily. They tend to activate the nerve endings inthe majority of consumers. The Laserscan and OFDA techniques are usedto determine the value of comfort factor, which is applicable infibers with less than 30 μm. Fibers with a high comfort factor (morethan 95%) are able to bend easily, which reduce the level of pricklesensation. Some studies have disputed the fact that diameterinfluence the softness of cashmere, alpaca, and wool ($ 150, 151,152).

2.3.2Effect of diameter distribution on yarn features

2.3.2.1Variation in the entire diameter of the fleece fiber

Studieshave shown that the diameter of fiber is not homogeneous. Accordingto Wood, 2003) diameter varies between 10 and 70 microns, which havebeen confirmed using a representative sample of wool. The value ofthe diameter is represented fairly as a normal distribution using theLaser Scan or the OFDA technique. This representation allowsresearchers to determine the degree of variation of the diameter ($153). The “standard deviation” is considered as the major measureof the level of variation. This measure can also be taken in terms ofthe coefficient of variation (CV). Although the two measuresmentioned above result in different values, they help researchersdetermine the actual variation in diameter. This reflection has beenconfirmed by the positive correlation between FD and diameter ($154).

Theapplication of SD in the determination of the diameter is done withinthe normal distribution. The normal distribution was standardized,where about 66 % of the fiber was isolated within a single SD and 95% of its represented in two SD from the FD values (Greeff, 2006). Thederived values of changes in diameter are considered to be indicativeof the actual variation. A high SD value is associated with extensivevariation in diameter of the fiber that is being assessed. A low SDvalue, on the other hand, is used to indicate that the level ofvariation in diameter is quite limited. The value of CV is expressedas a percentage. This figure is derived from the SD values, which isdivided by the FD. The CV value allows researchers to perform thecomparison of variations that occur in the diameter of a sample offiber that has dissimilar values of FD ($ 155).

Anincrease in the value of CV is directly proportion to changes in FD,irrespective of the processing performance of wool. The applicationof the rule of thumb has shown that a decrease in FD by one micron isassociated with an increase in CV value by approximately 5% ($ 156).The diameter of a sample of the fiber is considered as one of the keyfactors that influence its market price and the ultimate value. Theprice of wool increases with the decrease in the variation of itsdiameter. In addition, the demand for fiber increases with thedecrease in the degree of variation in its diameter ($ 157). Theincrease in demand, value, and price of fiber is attributed to thefact that a low level of variation in diameter is the actual measureof its overall quality. Buyers are always willing to pay some extramoney as a premium for fiber that has high CV and low SD values ($158).

2.3.2.2 Variation in diameter of staple fiber

Variationsthat are observed in diameter of wool occur within a single piece offiber. This variation is measured on the basis of the fiber diameterprofile (Brown, 2000). The FDP value of one piece of fiber is sharedby the entire staple. The profile acts as the lock form where allgroups of fibers connect to each other. All fibers that form the FDPvary in unison, which implies that the decrease or an increase in thesize of the diameter occurs in all of them ($ 159). The profile orFDP gives processors an insight into divergences that take placenaturally as the wool continues to grow (Brown, 2000). The economicsignificance of the FDP is attributed to its association with thestrength of the staple and the CV value ($ 160). In addition, the FDPhas an indirect effect on the economic value and the overall qualityof wool.

AlthoughFDP is correlated with the CV and the strength of the staple, it ispossible to evaluate it independently. Independent evaluation of FDPis achieved by segmenting the wool into different fragments of fiber.Individual fragments should have a length of about 2mm (Cottle,1991). After segmenting the wool, different fragments should beanalyzed in a sequential way. The process of analysis should focus onthe determination of the FD. The outcome of the process of analysisis amalgamated into the profile (Brown etal.,2000). The approach used in conducting the independent analysis ofthe fragments is based on the methodology known as OFDA. For example,the OFDA approach that has been modified makes it possible todetermine the diameter of a single piece of fiber. The diameter isdetermined at an interval of about 40 μm. The modified methodologyis accomplished using a machine referred to as a single fiberanalyzer ($ 161). Currently, the determination of FDP has not gainedpopularity in the textile sector and it is not done on a regularbasis. However, the FDP of wool is expected to be uniform. Wools witha uniform FDP are considered to be of a high quality.

2.3.3Effect of the length of the fiber on features of the yarn

Astaple length of the wool is one of the significant factors used todetermine the overall value as well as the quality of the fiber ($162). The measurement of staple length is usually taken inmillimeters (Thompson etal.,1988). ATLAS is a useful instrument that processors and researchersuse to quantify staple length ($ 163). The purpose of determining thevalue of staple length is to assess and indicate the processingperformance of wool. The length of the stable is positivelyassociated with the level of processing performance. In most cases,wool that has a long SL is considered to be desirable in the market