Comparison of the Vortex and Ring Spun Cotton Yarns and Their Knitted Fabric Properties

PEI Ze-guang()()

1 College of Mechanical Engineering,Donghua Univeristy,Shanghai 201620,China

2 Engineering Research Center of Advanced Textile Machinery,Ministry of Education,Donghua University,Shanghai 201620,China

Introduction

Vortex spinning,which is regarded as an innovative air-jet spinning technology,incorporates high-speed swirling airflow to insert twist into the fiber strand[1].With the advantages of the highly increased productivity,shortened process,and decreased number of operators,vortex spinning has become one of the most promising technological innovations in the yarn spinning industry[2-6].In vortex spinning,yarn with a core of parallel fibers held together by wrapper fibers is formed[7].Although the conventional ring spinning has exposed some disadvantages such as lower production speed and longer process compared with some unconventional spinning technologies,it has the widest spinnable count range and is currently the most widely used spinning technique[8].Advantages of vortex spinning and its products have challenged the leading position of the conventional ring spinning.Therefore,there is a great necessity to compare the vortex and ring spun yarns and their fabric properties to evaluate the vortex and ring spinning technologies and their products.Soeetal.compared the structures of vortex spun cotton yarns with ring yarns by observation with an optical microscope and explained the differences in measured yarn properties such as bulkiness,compression properties,and bending properties[9].Becerenetal.made an experimental comparison on the properties of the combed ring,compact and vortex yarns and their knitted fabric performances including bursting strength,abrasion resistance,and pilling[10].Erdumluetal.also compared the properties of fabrics made from combed ring and vortex spun yarns including bursting strength,dimensional stability,and pilling[11].In this paper,carded vortex and ring spun cotton yarn properties,including tensile properties,evenness,and hairiness,are investigated.Further,the properties of the knitted fabrics with the same structure produced using the carded vortex and ring spun yarns,including air permeability,drapeability,bursting strength,pilling and abrasion resistance,

are tested and compared.The carded yarns are spun with different process parameters from previous researchers to enrich the studies on the vortex fabric properties.In addition,comparison of some of the ring and vortex fabric properties,such as air permeability and drapeability has not been reported previously.The goal of this work is to provide a reference to the application of vortex yarns and fabrics and evaluate the latent capability of the vortex spinning technology.

1 Experimental

Cotton fibers with an UHML value of 29.32 mm and micronair value of 3.96 were adopted to spin 100% cotton yarns of Ne30 on the vortex and ring spinning system,respectively.The cotton fibers were subjected to three passages of drawing after being opened and carded.Vortex yarns were spun on the latest type of No.861 Murata vortex spinning frame taking the third passage sliver.Rovings made from the sliver were fed to a Rieter G33 ring frame to produce the ring yarns.The spinning conditions used on the vortex and ring system are given in Table 1.Yarn tensile properties were tested by the Uster Tensorapid 3 yarn strength tester (Uster Technologies AG,Switzerland).The gauge length was 500 mm and the testing speed was 500 mm/min.And 100 samples were tested for each type of the yarns.Yarn evenness was tested by the Uster tester.And 10 samples were tested for each type of the yarns and the testing speed was 400 m/min.The Uster tester was also used to test the yarn hairiness.The 10 samples were tested for each type of the yarns.The segment length was 10 m and the testing speed was 30 m/min.Plain-knit fabrics from the vortex and ring spun yarns were knitted by a sample circular knitting machine.The walewise density of the knitted fabric is 74 stitches/(5 cm) and the coursewise density is 52 stitches/(5 cm).Air permeability was tested by the YG461E digital air permeability tester (Ningbo Textiles Instrument Factory,China) according to ASTM D 737 standard.Fabric drapeability was tested by the XDP-1 drapeability tester (Shanghai New Fiber Instrument Co.,Ltd.,China) based on the testing standard FZ/T01045 of China.Bursting strengths of the fabrics were tested by the YG-031 bursting strength tester (Laizhou Electronic Instrument Co.,Ltd.) according to ASTM D3787 standard.Pilling test was conducted by the YG502 pilling tester (Nantong Hongda Experiment Instruments Co.,Ltd.,China) according to the testing standard GB/T4802.1 of China.Abrasion resistance was tested by the Y522 round disc fabric abrasion resistance tester (Changzhou No.2 Textile Machinery Factory,China) according to ASTM D3884 standard.All the yarn and fabric samples were conditioned under standard conditions ((20 ± 2)℃,(65 ± 2)% relative humidity) for 24 h before testing.

Table 1 The spinning conditions used to produce the vortex and ring yarns

2 Results and Discussion

2.1 Yarn tensile properties

Table 2 shows the tensile properties of the vortex and ring yarns.Surprisingly,the tenacity of the ring yarn is slightly lower than that of the vortex spun yarn,which is contradictory to the expectation that the tenacity of the vortex yarn is lower than that of the ring yarn.This may be due to the improper process parameters chosen for spinning the ring yarn.This result also indicates that under some conditions the tenacity of the vortex yarn can be comparable to the ring yarn.As for the elongation,it can be seen from Table 2 that the vortex spun yarn has a larger elongation than the ring yarn.In the ring yarn,fibers are helically bound together by strong transverse forces in between with obvious fiber migration.The fibers are difficult to slip between each other as the yarn breaks.This causes a relatively small elongation of the yarn.Consequently,the vortex yarn has a wrapped structure of a core of twistless,parallel fibers held together by surface wrapper fibers that helically wind onto the yarn core.As a result,fiber slippage between the core and wrapper fibers is expected to take place as the yarn breaks.This contributes to the increase of the yarn elongation.The work of rupture of a yarn is the work done to the yarn by the external force during the process of breaking the yarn.The work of rupture value of a yarn reflects the energy possessed by the yarn to resist the damage caused by the external forces.Our results show that the vortex yarn has larger work of rupture than the ring yarn,which denotes the vortex yarn is more capable of resisting the external damages.

Table 2 Tensile properties of the vortex and ring yarns

2.2 Yarn evenness and imperfection

Table 3 shows the evenness and imperfection values of the vortex and ring spun yarns.The results reveal that the vortex yarn has better evenness than the ring yarn since in the vortex yarn,and the parallel core fibers are bound together by the wrapper fibers tightly and evenly.The fibers are well controlled in the resultant yarn and the yarn shows a regular appearance.As for the imperfection,the vortex yarn has more thin places,fewer thick places and neps compared with the ring yarn.During the vortex spinning process,most of the linters and impurities in the fibers are removed from the spinning nozzle by the airflows.This results in a reduced number of the neps in the vortex spun yarn.

Table 3 Evenness and imperfection values of the vortex and ring spun yarns

Note: the “m” is short for mass； U stands for the irregularity of the mass with a cut length of approximately 1 cm

2.3 Yarn hairiness

Table 4 shows the hairiness index values of the vortex and ring spun yarns.With the increase of the hairiness length,the hairiness values of the vortex and ring yarns both decrease.As can be seen,the vortex yarn has much less hairiness of all lengths than the ring yarn.Another distinctive point is that the vortex yarn has no hairiness longer than 3 mm.In the vortex yarn,the long fibers converge to the yarn core which is tightly held and fixed by the wrapper fibers in the outer layer.This unique yarn structure gives the vortex yarn the feature of having less hairiness.

Table 4 Hairiness index values of the vortex and ring spun yarns

2.4 Fabric air permeability

Table 5 shows the properties of the fabrics made from the vortex and ring yarns.It can be seen that both the air permeability value and variation of the fabric made from the vortex yarns are higher than those of the fabric made from the ring yarns.The air permeability is evaluated by the flux of the air perpendicularly permeating the fabric in unit time.For the vortex fabric,the air can permeate the fabric from both the space between the adjacent yarns in the fabric and the space between the parallel core fibers in the yarn.While in the ring yarn,the fibers are tightly entangled and migrate in the radial direction of the yarn.As a result,the ring yarn has a more compact structure than the vortex yarn,which resists the permeation of air.This leads to a decreased value of air permeability for the ring fabric.

Table 5 Properties of fabrics made from vortex and ring yarns

2.5 Fabric drapeability

The drapeability of a fabric is the degree of the fabric edge drooping from the deadweight when the fabric drapes into the three-dimensional shape.The drapeability of a fabric is evaluated by the drape coefficient defined as the ratio of the area of the projected shadow of the fabric to the original area of the fabric.A smaller drape coefficient value indicates better drapeability of the fabric.The two types of the fabrics are cut into round samples and hanged onto the pedestal of the drapemeter.The shadow of the fabric sample is projected on the background when a light perpendicularly irradiates the fabric and its area can be obtained by an optical scanner and calculated.Due to the unbalanced internal forces of the stitches of the knitted fabrics,the edges of the fabrics are crimped and the drapeability tests are difficult to perform.To avoid the influence of the fabric crimp,a simple flatting treatment was performed to the fabrics before testing.From Table 5 it can be seen that the drape coefficient of the ring fabric is smaller than the vortex fabric,which means the ring fabric has better drapeability than the vortex fabric.The fabric drapeability reflects the stiffness of a fabric.A stiffer fabric has lower drapeability.When a fabric drapes,both the bending and shear effects of the yarns in the fabric take place.Therefore,the bending property,and the slippage and rotation of the intersectional points of the yarns in the fabric have evident influence on the fabric drapeability.Since the two types of the fabrics are of the same structure,the intersectional points of the yarns in the vortex and ring fabrics have similar degrees of slippage and rotation.Therefore,the drapeability values of the vortex and ring fabrics are mainly influenced by the bending property and stiffness of the yarns.The vortex spun yarn is considered to be stiffer than the ring yarn.This leads to the lower drapeability of the vortex fabric.

2.6 Fabric bursting properties

Bursting is the destruction of a fabric when it is gradually compressed and destroyed by the concentrated load.Bursting strength and bursting elongation are important indicators for the mechanical properties of knitted fabrics.In the testing process,the fabric is subjected to forces in all the directions along the fabric.As can be seen from Table 5,the bursting strength,elongation,and work of rupture of the vortex fabric are all higher than those of the ring fabric.It is known that with the same fabric structure,higher breaking elongation of the yarn results in higher bursting elongation of the fabric.In this situation,the components of the tensions of the fabric in the direction of compression are higher.This leads to a higher bursting strength.According to the results of the yarn tensile properties,the vortex yarn has higher tenacity and elongation than the ring yarn.This must be the reason for the better bursting properties of the vortex fabric than the ring fabric.

2.7 Fabric pilling

Figures 1 and 2 illustrate the surfaces of the vortex and ring fabrics before and after the pilling test,respectively.It can be seen that the pilling resistance of the vortex fabric is much better than the ring fabric.The surface of the vortex fabric is only covered by a layer of unobvious hairiness.The pilling resistance can reach grade 4.In comparison,the whole surface of the ring fabric is covered by pills with different sizes and distribution densities.The pilling resistance is only of grade 1/2.The pilling of a fabric is resulted from the entanglement of the fibers on the fabric surface when the fabric is under friction.The fibers on the fabric surface can be the hairiness of the yarns making the fabric or the loose fibers pulled out from the yarns when experiencing friction.According to the yarn hairiness results,the vortex yarn has much less hairiness than the ring yarn.Besides,since the core fibers of the vortex spun yarn are tightly held by the wrapper fibers,the fibers are not prone to being pulled out.This leads to a smaller probability to pill for the vortex fabric.Comparatively,the ring yarn has more hairiness,especially the long hairiness.The fibers are not as tightly fixed in the yarn as those in the vortex yarn.Therefore,the fibers are prone to being pulled out and tend to tangle together.As a result,fabric pilling is more likely to occur in the ring fabric.

(a) Before the pilling test (b) After the pilling test

(a) Before the pilling test (b) After the pilling test

2.8 Fabric abrasion resistance

The weight loss of the ring fabric is lower than that of the vortex fabric after the abrasion resistance test,as shown in Table 5.This denotes that the ring fabric is more abrasion resistant than the vortex fabric.This conclusion could also be drawn by assessing the surface appearances of the fabric samples after abrasion.Figures 3 and 4 show the surface appearances of the vortex and ring fabrics after the same working rounds of the abrasion disc,respectively.The appearance of the ring fabric is better than the ring fabric sample after abrasion.Table 6 lists the number of holes on the vortex and ring fabrics.There are fewer holes on the ring fabric than the vortex fabric after the same working round of the abrasion disc.The core of the vortex yarn is considered to be composed of parallel fibers with fewer twists.After the wrapper fibers in the outer layers of the vortex yarns break during the abrasion,the core fibers are exposed to the abrasion and they are easier to break.Comparatively,the ring yarn has a structure with the fibers helically entangled and twisted.The abrasion resistance of the ring yarn is consequently more even.This may be the explanation for the better abrasion resistance of the ring fabric than the vortex fabric.

(a) 100 rounds (b) 300 rounds

(a) 100 rounds (b) 300 rounds

Table 6 Number of holes on the surfaces of the vortex and ring fabrics during the abrasion resistance test

3 Conclusions

In this paper,the vortex and ring spun cotton yarn properties in terms of tensile properties,evenness and imperfections,and hairiness are compared.Further,the two types of yarns are made into plain-knit fabrics.The fabric properties in terms of air permeability,drapeability,bursting strength,pilling and abrasion resistance,are tested and compared.The results show that under some conditions the tenacity of the vortex yarn can be comparable with that of the ring yarn.The elongation and evenness of the vortex yarn are better than the ring yarn.The vortex yarn has much less hairiness than the ring yarn.The vortex fabric has better air permeability,bursting properties,and pilling resistance than the ring fabric,while the ring fabric shows better drapeability and abrasion resistance than the vortex fabric.The comparison results reveal that the vortex spinning is a promising technology with satisfactory product qualities.

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