physical characteristics of cotton/polyester core spun yarn made

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AUTEX Research Journal, Vol. 9, No1, March 2009 © AUTEX2.3. Preparation of yarnUsing a conventional ring spinning process, core yarns wereprepared on a ring frame by passing polyester filament yarnthrough the front roller nip of a ring frame [10,11] and rovingthrough the drafting zone of the ring frame as shown in Fig. 1.The roving was prepared by passing the fibres through themodern blow room, carding machine, modern combers, drawframe, and speed frame. A total of six different types of coreyarns were prepared on the ring frame under ideal conditionsby varying the core–sheath ratio. Using the same core–sheathratio, six core yarns were also prepared [12] on a Murata Air-Jet Spinner MJS802 as shown in Fig. 2. Using the same cottonsliver at the back of the main drafting zone and polyesterfilament passing through the front drafting roller, 30 s Ne coreyarns were prepared. Parameters such as drafts and denierof polyester core yarns were varied. The twist multiplier andother spinning process parameters were kept unchangedthroughout all the yarn manufacturing processes.2.4.2. Unevenness and imperfectionsMeasurements of yarn unevenness and imperfections weretaken using an Uster-4. The yarn irregularity in terms of U%and the imperfections in terms of thick places, thin places,and neps were evaluated.2.4.3. Yarn count and count strength productYarn count was measured with the help of wrap reel andcount strength product by using a good brand of lea strengthtester. Twenty (20) readings per sample were taken to get theaverage value.2.4.4. Core yarn initial modulus and core yarn energy tobreakThe core yarn initial modulus and core yarn energy to break ofdifferent core yarns were tested on an Instron machine.2.4.5. Scanning electron microscopy (SEM) photographsCross-sectional views of 2/30 Ne yarns were observed undera scanning electron microscope (SEM) and photographs weretaken. The photographs were evaluated using computer aidedsoftware. The perimeters of photographs covered by cottonas well as covered by polyester were measured. Thenpercentage perimeters covered by cotton were calculated andcompared.3. Results and discussion3.1. Count strength productFigure 1. Core yarn prepared by ring spinning.Figure 2. Core yarn prepared by air-jet spinning.30 s Ne average count was prepared for this study. By usingthe same mixing and the same machine, 100% cotton yarnwas produced for comparative study. After preparation, allsingle core yarns were doubled on a T.F.O. (Vijay Laxmi)machine under mill conditions to prepare 2/30 s Ne yarns .2.4. Yarn quality evaluation2.4.1. Breaking strength and extensionThe breaking strength and extension of the yarn sampleswere measured on an Instron tensile tester using the standardprocedures in accordance with ASTM D 2256.The lea strengths of different core yarns were tested on anelectronic lea strength testing machine. From the results itwas observed that introducing a very minor amount of filament(15%, 30 den.) at the core reduced the CSP value of the ringyarn by about 15-17% compared to 100% cotton yarn.Thereafter it was seen that a further increase in filaments atthe core by about 25-40% caused the CSP values to increasesignificantly, compared to 100% cotton yarn, by about 29-31%when 44 den. was used and 31-36% when 70 den. yarn wasused at the core. This was because of simple elongation offilament yarn at the initial state of loading of the yarn, and thecomplete load was shared by the cotton at the sheath, whichwas broken very fast, and therefore made the yarn weak. Withthe further increase in filament denier at the core and fewercotton fibres at the sheath, the maximum load was shared bythe straight synthetic filaments which were stronger than thecotton, and therefore the strength was increased comparedto the cotton yarn.If we compare the CSP values of drawn and crimped coreyarn, no significant difference was observed.It was also observed that the CSP values of air-jet core yarnsmade from polyester core yarns were all weaker than thoseof 100% cotton yarn. This was because of low binding forcesbetween the fibres due to false twisting, generally used in thespinning process. In air-jet yarns it was seen that when weincreased the denier of drawn yarns from 30 den. to 70 den.the core yarn showed between 29 and 14% lower strengththan 100% cotton yarn. With crimped core filaments, thestrength was between 25 and 11% lower when we changedthe denier from 30 den. to 70 den.http://www.autexrj.org/No1-2009/ 0305.pdf15
AUTEX Research Journal, Vol. 9, No1, March 2009 © AUTEX4500400035003000250020001500100050003.2 Single yarn strengthCSP30/DR 44/DR 70/DR 30/CR 44/CR 70/CR 100% CFigure 3. CSP values of drawn and crimped core yarn.Poly/RFpoly/AJFrom the results it was observed that when 15% (30 den.)filaments were introduced at the core, yarn strength wasreduced by about 15 to 17% for ring core yarn in both drawnand crimped yarns compared to 100% cotton yarn strength.When the percentage of filament was 25% (44 den.) therewas absolutely no gain or loss in strength for both drawn andcrimped yarns compared to 100% cotton yarn. When thepercentage of filaments was nearly 40% (using 70 den.) thenthe strength of core yarn was increased for both drawn andcrimped yarns by about 43% compared to 100% cotton yarn,which is clearly seen from Fig. 4. It was observed that ringcoreyarns always showed 15–33% greater single yarnstrength than air-jet core yarn. It was also clear that as thepercentage of polyester was increased at the core, whetherby crimped or drawn filaments, the strength increased inproportion to the increase in denier at the core.It was observed that in the case of 30 den. air-jet core yarn,the strength fell to 50% compared to 100% cotton ring-spunyarn strength, which was considered a major setback for theintroduction of only 15% filament at the core compared to100% cotton ring-spun yarn. When we increased the filamentpercentage at the core, the difference was gradually reduced:with 25% filament at the core the strength difference wasabout 25% and with 40% filament at the core the strengthdifference was reduced to 7%, which may not be consideredsignificant.7006005004003002001000Single Yarn Strength30/DR 44/DR 70/DR 30/CR 44/CR 70/CR 100%CFigure 4. Single yarn strength.3.3. Elongation percentage of core yarnPoly/RFpoly/AJFrom the results it was observed that in all the ring core andair-jet core yarns (polyester), the increase in filament at thecore increased the elongation percentage of the core yarns.There were no trends observed in the case of air-jet and ringcore yarns or in crimped and drawn yarns. From the results itwas also observed that when 15% (30 den.) filaments wereintroduced at the core, yarn elongation was increased by 20%to 80% for ring core and air-jet core yarn with drawn andcrimped filaments at the core compared to 100% cotton yarn.When the percentage of filament was 25%, the increase inelongation was observed to be about 80–100% for both withdrawn and crimped yarns compared to 100% cotton yarn.When the percentage of filaments was nearly 40% then theelongation of core yarn was increased for both drawn andcrimped yarn to about five times that of 100% cotton yarn.This was because of the introduction of filaments at the corewhich was considered to provide high elongation of the yarncompared to 100% cotton fibres. The properties of filamentswhich contributed the lion’s share of the tensile properties ofcore yarn are presented in Table 1.2520151050Elongation % of core yarn30/DR 44/DR 70/DR 30/CR 44/CR 70/CR 100% CFigure 5. Elongation % of core yarn.3.4. Core yarn energy to breakPoly/RFpoly/AJEnergy to break of different core yarns was tested on an Instronmachine. From the results shown in Fig. 6 it was observedthat when the percentage of filaments (polyester) was only15% at the core no significant differences were observed inenergy to break compared to 100% spun cotton yarn. Whenthe percentage of filaments at the core was increased by25%, (44 den.) there was a drastic increase in the energy tobreak, which was observed to be 107–125% for ring coreyarn, and when the filament percentage was increased by40% at the core the value was increased by 10–11 times thevalue for 100% cotton yarn.Air-jet core yarn with up to 25% filament at the core did notshow any change in energy to break compared to 100% spuncotton yarn, but when the percentage reached 40% at thecore there was a drastic increase in the energy to breakobserved for the air-jet core yarn, which was nearly 6-8 timesmore than that for 100% cotton yarn.Generally, a lower percentage of filament at the core may notcontribute more to the strength of the yarn, but a greaterelongation of the yarn jointly provided energy to break at perwith 100% cotton yarn. When the percentage of filament wasincreased substantially at the core, both strength andelongation jointly led to higher energy to break.Crimped yarns always showed higher values of energy tobreak than drawn yarns at higher percentages of filaments atthe core: when the percentage of filament at the core was40%, the core yarn energy to break increased by 33% and15% for ring core and air-jet core yarns respectively.http://www.autexrj.org/No1-2009/ 0305.pdf16
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physical characteristics of cotton/polyester core spun yarn made

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