Liquid Sorption and Transport in Woven Structures

Investigations in liquid sorption and transport were performed with three different variants of terry woven structures. Terry fabrics were produced using linen warp pile yarns and cot­ton or linen ground warps and wefts. The process of liquid sorption from the first moment when the water drop beads up the fabric’s surface until there is a complete loss of the drop’s specular reflectance and an absolute absorption of the liquid i.e., when the wetted spot re­mains stationary.

A method for measuring dynamic water absorption in and through terry fabric is suggested. The action of terry fabric in contact with a liquid drop and liquid trans­port through it depends on the structural characteristics of the terry material, the kind of impact or finishing operation and its intensity.

The character of liquid penetration through terry fabric is different when analysing grey woven material, and which is affected by in­tensive impact/finishing. All the kinds of regressions investigated generally showed a very good match with experimental data. The results of the research determined the dynamics and character of the sorption process in woven terry fabrics and could be used for creating new textiles with desired properties.

Key words: impact/finishing, liquid transport, sorption, structure, terry fabric.

Introduction

Textiles with high liquid sorption quali­ties, which absorb dyes and chemical finishes could be used for applications in direct contact with human skin in order to help cool the body by readily absorb­ing moisture or perspiration. Absorption and permeability properties as well as moisture transmission through textiles are important for textile design and espe­cially relevant for the comfort of cloth­ing created for wear or use in damp and warm environments, such as bathroom and sauna clothes, headdress, footwear, towels as well as for medical and sport textiles, amongst others [1 - 4].

The interaction of liquids with textile could involve some fundamental physi­cal phenomena: wetting of the fibre sur­face, transport of the liquid into assem­blies of fibres, adsorption of the fibre sur­face, and diffusion of the liquid into the interior of the material [5]. On the basis of the relative amount of liquid and mode of liquid-fabric contact, the wetting and wicking processes can be divided into such groups: wetting/wicking from an in­finitive liquid reservoir and from a finite (limited) liquid reservoir. The second one is exemplified by a drop wetting/wicking into the fabric.

Generally terry materials absorb water perfectly. Of course, the absorption ca­pacity depends on the yarn material and type as well as the fabric structure [6]. It was shown that the type of yarn used in terry fabrics had the most significant effect on static water absorption proper­ties. In [7] Karahan experimentally in­vestigated the dynamic water absorption

properties of terry fabrics using a method of electronic balance. It was assumed that water the absorption speed for each time interval would provide a more direct un­derstanding of the dynamic water absorp­tion behaviour of the textile. It was found that depending on the yarn type, around 26 - 40% of the total water absorption capacity is absorbed in the first 10 s. Af­ter 30 s, water absorption continues at a decreased speed. Water absorption con­tinues even after 300 s but at a very low rate, which cannot be considered from a practical point of view.

The transport of a liquid into yarns and fabrics may be caused by external forces or by capillary forces, i.e. wicking. Be­cause capillary forces are caused by wet­ting, wicking is a result of spontaneous wetting in a capillary system [5]. The kinetics of capillary filling depends on the pore radius [8]. During wicking, flat continuous filament yarns show typical capillary liquid flow due to the number and length the filaments running paral­lel to each other [9]. In yarns the way in which filaments pack together deter­mines the amount of void space between filaments [10], and an increase in the number of filaments, yarn tension and twist has a significant effect on the yarn wicking performance. Microscopic ex­amination proved that yarns with more twist exhibited a reduced wicking trend with a sudden increase in wicking per­formance at high twist levels due to spiral wicking [9].

The degree of hydrophility of towel ma­terial has already been investigated us­ing the sinking test [11]. The experiment showed that the type of softener affects

the degree of hydrophility. The sinking time of towels produced with dyed yarns was higher than that of towels dyed in a fabric form, and the hydrophility de­gree of uncut pile towels was found to be better than that of velvet towels. Be­sides this, it was determined that the pile height decreases the sinking time. How­ever, there must be a limit depending on the yarn number, twist, type of raw mate­rial and density of the pile height, beyond which the hydrophility degree tends to decrease. It was found that the washing process appeared to be an important pa­rameter in defining the sinking time – in washed towels it became lower than that of towels which did not undergo any washing procedure.

Moisture transmission through textiles along with wetting and wicking play a significant role in maintaining thermo­physiological comfort. Scientific under­standing of the processes involved in moisture transmission through textile materials, as well as factors affecting these processes and mathematical model­ling are significant in the design of new textile systems [1, 2]. It was determined that the vital lack of correlation between water vapour permeability, the thickness of knitted fabric and surface porosity re­sults from the character of media trans­port by free convection and the general high porosity of knitted fabrics [12]. The influence of soaking in water to realise the optimum swellability of linen yarns in fabrics was studied in [13].

In many process techniques and end-use characteristics, the surface wettability of textiles and technical fibres is a key fac­tor. In dyeing, finishing or coating proc‑

esses, the wetting properties affect the process parameters and final qualities of textiles. The wettability of long fibres like flax, ramie, jute, sisal and sunhemp has already been determined and com­pared [ 14]. It was found that the wettabil­ity of fibres depends on the properties of the binder, the properties of the fibre sur­face and the nature of the fibre. With an increase in the concentration of polyvinyl acetate solution from 5 to 10 %, the wet­tability decreased in all the natural fibres studied, depending on the chemical and physical characteristics of the fibre.

The moisture content of fibres and the be­haviour of liquid in contact with textiles are very important for both the processing and use properties of products especially for analysing test results of the new fibres and textiles for medical applications that could well possess biofunctions, carry medications, act as cell culture scaffolds, etc. [3]. [15] deals with the water inhibi­tion of fibres, in which the water that in is within cell walls, inter-fibre spaces, or pores is measured.

The sorption of a drop can indicate the wettability of a textile material either by the time of its sorption by the fabric or by the area of the wet spot formed by the liq­uid [16]. Kissa states that in cases where the liquid can diffuse into the fibres, the kinetics of sorption and liquid transport are complicated. Diffusion of the liquid into fibres accelerates the sorption; how­ever, the spreading rate of liquid within the fabric is reduced because absorption in fibres reduces the volume of liquid available for spreading in capillary spac­es, which causes the swelling of fibres and decreases the spaces between them. The wettability of fibres with respect to water is the most important factor deter­mining the detergency of oil in an aque­ous bath; other factors are the viscosity of the soil, the detergent, wash temperature, agitation, etc.

In spite of the interest in the absorption process of textiles, no research has been conducted into the absorption of terry fabrics regarding various impacts or fin­ishing, especially washing, softening and tumbling. The aim of our study was to conduct experimental investigations into the water sorption process and liquid transport in loop pile fabrics with respect to to various impacts/finishing operations and their duration.

Experimental

Object and method of investigation

The experiments were conducted using the three variants of terry woven struc­tures presented in Table 1. The main structure investigated was that of pure linen terry because of the excellent ab­sorption properties of flax fibre and the popularity of such an assortment. The linen/cotton structures were analysed as additional items with a view to including larger amounts of terry material affected by various types of industrial finishing. Table 2 shows the impacts/finishing ap­plied to the terry fabrics.

During the macerating procedure, the specimen was placed into water for a time necessary to complete the macerat­ing of the material. The detergent Felosan NOG (CHT R. Beitlich GmbH, Germa­ny) was used for washing at a tempera­ture of 60 °C, over a period of 60 min­utes. The softening procedure was per­formed using silicone conditioner Tub­ingal SMF silicone conditioner (CHT R. Beitlich GmbH, Germany) over a period of 60 min, at a temperature of 40 °C. The purpose of softening is to give a soft and fluffy surface to the material. The tum‑

bling operation gives a fuller volume and a more cushioned handle to the textile. To achieve the terry fabric softness that is in great demand nowadays, the sam­ples were washed with detergent, condi­tioned, centrifuged and then tumbled for 5 periods of 30 to 150 min.

The experiments were performed using a SMZ 800 Nicon Stereoscopic Micro­scope and Coolpix 4500 Digital Camera; 7.0 PE-Live software was applied for analysis of video records. The absorption process was filmed from the start mo­ment (SM) until the last moment (LM), i.e. from the moment when the drop of distilled water (of 0.110 g) fell onto the surface of the fabric until it was abso­lutely absorbed by the fabric. The height of the falling was as minimal as possible (it was chosen so that the drop could not touch the dropper and the surface of the fabric at the same moment). The test in­struments used in the experiments are presented in Figure 1. Two experiments were performed: filming from the upper side of the fabric (see Figure 1.a) and filming from the underside of the fabric (see Figure 1.b). The areas of the liquid spots were measured by investigating

pictures of video records, and changes in
the spot’s area over time were calculated.

Polynomial, linear, logarithmic, power, and exponential types of regressions, which can describe the results, were ana­lysed.

n Results and discussion

Sorption dynamics of pure linen grey fabrics, as well as after macerating and after washing procedures

The structure of loop pile in grey fabric is of regular geometry – the loops are rigid and range perpendicularly to the base of the fabric. When in contact with liquid this fabric acts in a very special manner. Figure 2 shows the water absorption of grey terry fabric (C1 variant) over time. Further results of the absorption process, in which the fabric was filmed from the upper side, are presented.

It takes 370 s from the start moment to a complete loss of the drop’s specular reflectance and the occurrence of abso­lute absorption when the spot becomes stationary. It is important to note that the rigid loop pile in grey fabric that was not affected by any liquid impact or finish­ing, which had been in previous contact with the drop, demonstrated resistance to water uptake. We determined that the drop holds its full specular reflectance for approximately 5 seconds and even up to 15 seconds from the SM till the moment when the specific shape of the drop disap­peared and only a sloppy or wet spread­ing spot was observed. The research [5] stated that most textile materials are not isotropic, thus the spreading liquid does not usually form a circle with a well de­fined radius; besides, the wicking process is kinetically quite different when capil­lary penetration is accompanied by the diffusion of the liquid into the fibres. We found that the wetting pattern is uniform at the beginning of the sorption proc­ess. After the period when the drop loses its full specular reflectance, the liquid spreads almost as a regular continuous front, and an obvious “fingering” pat­tern was not determined. Supposedly, the capillary spaces in terry fabric are not uniform and the irregularity of pores between fibres and yarns as well as the irregularity of the distribution of pores could change the wetting progress. The water was absorbed at an uneven speed in all the intervals investigated, from SM till LM. At the beginning, i.e. for a period of SM to 10 s the absorption runs slowly.

Such behaviour between the drop and fabric surface is inherent only for grey fabric. Later on the sorption progresses. During the period of 10 to 40 s the spot’s area changed 1.38 times. The full absorp­tion process took 370 s and it is the long­est wetting compared with all other in­vestigated variants. When analysing the SM/LM interval, it was observed that the change in the spot’s area had increased by 225.9%. The polynomial relationship with the highest determination coeffi­cient, R² = 0.9881, was determined be­tween the water absorption time and the change in the spot’s area. Other kinds of equations investigated also showed high determination coefficients, except the ex­ponential one.

Macerating and washing changed the terry structure. It was determined that the sorption shortened very significantly, i.e. almost twice in the macerated sample (till 190 s) or even much more in samples washed in water for 10, 30 or 120 min (till 130 s). Figure 3 shows pictures of the video record of macerated terry fabric (C2 variant). During the first inspected period from SM to 10 s, the spot’s area increased by 29.9% and 42.6% after mac­erating (C2 variant) and washing in water for 30 min (C4 variant), respectively. The change in spot area of variants C2 and C4 appeared to have increased by 282.5 % and 211.3 %, respectively which analys­ing the period SM - LM. The change in the LM’s in the spot area in the macerated

fabric was the largest compared to all the other changes obtained in pure linen fab­rics (see Figures 2, 4 - 6). Such values re­veal how significantly the fabric was in­fluenced by even short and not intensive impacts, such as the macerating one. The highest determination coefficients are R² = 0.9981 (C2 variant) and R² = 0.9956 (C4 variant), which are best described by polynomial equations; but some other kinds of equations also show a very good match with the experimental data. The speed of change in the spot’s area in C2 and C4 fabrics is not the same. The peak of water spreading was observed at the beginning, i.e. for a period of SM - 10 s and at the end of the process, i.e. after 130 - 190 s in macerated samples. Here the changes in the spot’s area increased 1.30 and 1.37 times, respectively. The fabric washed in water (for 30 min) showed absorption with a constantly de­creasing speed during the period inves­tigated: at the beginning (SM - 10 s) the spot’s area increased 1.43 times, whereas over a 100 s - LM period the spot’s area increased 1.07 times.

Wetting through washed, softened, and calendered terry structures

The structures of terry fabrics after fin­ishing operations were investigated: washing with detergent, softening, and calendaring. Figures 5 & 7 show the absorption dynamics of terry fabrics af­ter washing with detergent and softening (B7, C7) as well as after the calender­ing procedure (B13). During all the in­dustrial washing cycle, which includes such impacts as water, mechanical, heat, and chemical, modification of the terry structure occurs. The additional factor of softening conditions the loss of loop pile stiffness throughout, resulting in the terry fabrics becoming soft and gentle. Calen­dering, by contrast, decreases the pores between yarns and fibres, with the loops being bent and flattened to the base of fabric, and decreases the thickness of the

textile. When pure linen and linen/cotton terry fabrics were analysed after washing with detergent, and softening, calendar­ing, the water absorption continued for 130 s whereas only 70 s after calendar­ing, i.e. nearly 3 times and in some cases more than 5 times longer compared to grey fabrics, respectively. The sorption speed is highest at the beginning, i.e. up to 10 s in washed and softened fabrics. During the period of SM - 10 s, the spot’s area changed 1.34 (C7 variant) - 1.32 (B7

variant) times. Later on the wetting pro­ceeded more slowly. Consequent decel­eration was especially visible in the case of pure linen terry fabric. Although these two curves (see Figure 5) correspond to the different fabric structures, both fab­ric samples showed the same character of water sorption over time, except LM; here the spot’s area changed by 190.3% for the C7 fabric and 221.3% for the B7 fabric. Regression analysis was applied to the experimental data, and the poly‑

nomial curves showed a perfect match with the experimental data; but very high determination coefficients proved that this is a very good or good match for both fabrics with respect to the other regressions under investigation: linear, logarithmic, power, and exponential. It was found that R² = 0.9977 (polynomi­al) - 0.8635 (exponential), which is the investigated data for the C7 variant, and R² = 0.9979 (polynomial) - 0.8731 (loga­rithmic), for the B7 variant.

The calendered fabric started to absorb water at a high speed, which then de­creases continuously till LM. In contrast with the washed and softened fabrics, the calendered one’s absorption finished with an increase in the area of the spot of 131.7% (see Figure 7). It may be conditioned by alterations in the fab­ric structure after calendaring, during which the loop pile lost its looseness, becoming smoother and tighter, and as a consequence the rigidity of the textile increased and the air spaces decreased significantly. All the kinds of regressions investigated showed a very good match with the experimental data: R² = 0.9986 (power) - 0.9375 (exponential).

Absorption behaviour of tumbled fabrics

The structure of the fabric after tum­bling is modified much more compared with other impacts or finishing. Tum­bling gives a fluffy handle and softness to the textile. The spaces between loops and yarns increase, the loops become bulk and sometimes a spiral or snarl loop structure can appear after this procedure.

15 pure linen and linen/cotton woven structures were investigated for various tumbling times, from 30 min to 150 min (see Table 2). Figure 8 shows pictures of the SM after 40 s and 70 s (LM) of tumbling terry fabrics (C10 variant). When investigating video records, it was found that the behaviour of liquid in contact with tumbled terry woven structures is different compared with other variants. In all tumbled samples the absorption process shortened con­siderably – by 5.3 times compared with grey fabrics. The spot became still after 70 s in all tumbled fabrics despite further tumbling and the fabric structure. As this absorption is very quick, it was divided into 5 intervals from SM to LM, i.e. after 10, 25, 40, 55 and 70 s. Figures 6 & 9 show the absorption process of different structures of terry fabrics tumbled for 90

min. The results of absorption when the tumbled fabrics were filmed from the upper side will be presented primarily. It was determined that the changes in the spot’s area increased in the follow­ing intervals: 54.1 - 103.9% (A10 vari­ant), 50.9 - 123.5 % (B 10 variant), and 55.0 - 132.4% (C10 variant). The liquid was absorbed very quickly at the begin­ning – during the first 10 s. For all the tumbled samples, regardless of the tum­bling time, the absence of the drop’s specular reflectance from the moment when it touched the surface of the fab­ric was determined. The tumbled fabrics snatched and sucked the liquid instantly. As is evident from Figures 6 & 9, dur­ing the first time interval (SM - 10 s) the change in the spot’s area increased sig­nificantly in all tumbled samples, i.e. by 1.55 (C10 variant) - 1.51 (B10 variant) times, but later on an evident and conse­quent decrease in the absorption speed was noticeable. During the final time in­terval (55 - 70 s), the absorption speed increased only 1.05 (B10 variant) - 1.03 (A10 variant) times. Besides this, the change in the spot’s area in LM reached only 103.9% (A10 variant), which is the lowest value compared with the other tumbled variants: C10 and B 10, as well as with all other fabrics affected by the various impacts/finishing (see Figures 2, 4 - 7 and 9). Generally, when analysing LM, the values of changes in the spot’s area in tumbled fabrics are lower com­pared with values in the LM of all the other variants investigated, except calen­dered fabric, where the difference is not statistically significant. The highest de­termination coefficients of regression for A10, B10 and C10 fabrics are respective­ly R² = 0.9995 (logarithmic), R² = 0.9965 (logarithmic), and R² = 0.9973 (polyno­mial). Such changes in the absorption of tumbled fabrics can be explained by the complex of long lasting impacts influenc­ing the woven structure and, hence, the fabric’s behaviour in contact with liquid.

Liquid transport in woven structures

With the purpose of analysing how a liq­uid penetrates a terry woven structure, an experiment was conducted using the scheme of instrument arrangement pre­sented in Figure 1.b. A drop of liquid was dripped onto the surface of the fabric, and the absorption process was analysed by filming it from the underside of the textile. A video record was made from the dropping moment till the last mo­ment when the area of the wetted spot remained stationary on the underside.

In this experiment the start moment co­incided with that mentioned before. Of course, it takes some time for the liquid to run through the fabric and to appear on the under side of the textile. Such an ex­periment was conducted with fabrics C1 and C10. Figures 2 & 6 show the change in the spot’s area with respect to the time when the textile was filmed from the un­derside. It was determined that the spot become visible on the underside of the fabric after 3 - 4 s and 2 s from the mo­ment when the drop touched the surface of the upper side of the grey and tumbled fabric, respectively. With the purpose of relating the results and to compare them, the start moment was the same as that used in the experiments filming the be­haviour of liquid from the upper side of the fabric. It was found that the change in the spot’s area increased from 21.6% to 246.9% in grey fabric (see Figure 2). The largest increase in the area of the spot (1.38 times) for grey fabric was determined in the second time interval (10 - 40 s), as in the experiment when the fabric was filmed from the upper side. Afterwards the speed of the spreading of the liquid slackened; the spot became still after 370 s. Trends of changes in the spot’s area are similar, but the areas of the spot are slightly higher on the underside of the fabric; however, the differences are not statistically significant.

It was found that the change in the spot’s area for tumbled fabric with respect to the SM/LM is 52.0 - 172.7%, in which the underside of the fabric was filmed. The water was absorbed at a constantly decreasing speed in all the time peri­ods inspected in both experiments (see Figure 6). At the beginning, i.e. in the time interval SM - 10 s, absorption oc­curs at the highest speed, i.e. the spot’s area changed even 1.52 times on the un­derside of the fabric. It was determined that the area of the spot in tumbled fab­ric increased till 185.8 mm² (LM) on the underside of the fabric, whereas during filming from the upper side, it increased from 68.2 mm² (SM) to 158.3 mm² (LM). The absorption character is similar on the upper as well as on the underside of the fabric. The statistically significant differences between the values of spot area were determined from the 25th s of observation.

Statistical analysis of experimental data

The experimental results were statisti‑
cally evaluated at the confidence level of

α = 0.95. Full statistical analysis was per­formed and the standard deviation, coef­ficient of variation, absolute error, and relative error were calculated.

Statistical analysis of the experimental data received while filming the fabric from the upper side showed that the co­efficients of variation results for changes in the spot’s area in many cases did not exceed 5.0% and varied in the interval of 2.0 - 7.0%; except some cases where they reached higher values, but did not exceed 10.6%. The relative errors varied in the interval 2.1 - 7.7%, except several cases where the values went up to 11.1%. In­vestigation of the experimental results re­ceived while filming the fabric from the underside showed that the coefficients of variation of changes in the spot’s area varied in the interval 3.2 - 8.8%, and the relative errors varied in the interval 3.3 - 9.2%.

Conclusion

· Application of the suggested method for measuring the dynamic water ab­sorption of terry woven fabrics ena­bled to analyse and evaluate the ab­sorption speed and changes in absorb­ency with respect to time as well as to investigate and interpret the sorption ability of the fabric.

· The absorption process of pure linen and linen/cotton fabrics depends on the fabric characteristics as well as on the kind and intensity of impact/ finishing. A significant difference ex­ists in the absorption capacity of the different fabric treatments or impact number.

· The absorption process ran more quickly in fabrics affected by more and intensive impacts/finishing. It was found that the absorption proc­ess continued longest – even till 370 s – in grey pure linen terry fabric. In macerated fabric and fabrics washed in water without chemical treatment (independently to washing duration) or using detergent and softener, the absorption process was shorter - till 190 s and 130 s, respectively. The tumbling operation, irrespective of its duration, shortened the absorption process considerably – by more than 5 times compared with grey fabric.

· The pure linen grey fabric that not been affected by any impact like wa­ter, heat, mechanical or chemical in contact with the drop demonstrated resistance to liquid uptake. It takes

approximately 5 - 15 s for the drop to lose its full specular reflectance as well as to transform into a soppy glossy surface on the upper side of the fabric. In contrast an absolute absence of a drop’s specular reflectance from the moment the drop comes in contact with the surface of a tumbled fabric, despite the fabric’s structure and tum­bling time was determined.

· The change in the wetted area in­creased by 12.6% during the first 10 s of investigating pure linen grey terry fabric, whereas an increase of 29.9 - 55.0% was obtained for fabrics impacted by macerating, washing in water (in 30 min), washing with deter­gent and softening or tumbling (in 90 min). When analysing the full period of absorption, the highest value of change in the spot’s area (by 282.5%) was obtained in macerated fabric.

· When investigating the start/last mo­ment, the change in spot area on the upper side of the fabric increased from 50.9 - 55.0% to 103.9 - 132.4% in dif­ferent structures of tumbled terry fab­rics.

· Many kinds of investigated regres­sions showed a very good match with experimental data: determination co­efficient R² = 0.9995 - 0.9881. Mainly the results are best described by poly­nomial regressions, but in some cases the logarithmic or power equations represent experiments the best.

· With the aim of determining how a liquid runs through a textile, pure linen grey terry fabric and one which had been tumbled were investigated by analysing the change in the spot’s area from the underside of the fabric. The same tendencies of absorption character and dynamics, compared with the results received from video records obtained from the upper side of the fabric, provide the possibility of obtaining a better understanding of dynamic water absorption properties and liquid transport in terry woven structures.

· Statistical analysis of experimental data showed that the coefficients of variation with respect to results of change in the spot’s area varied in the interval 2.0 - 10.6%, mostly not ex­ceeding 5.0%. The relative errors in many cases varied from 2.1 % to 7.7%.

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Spindle Diameter and Spindle Working Period

Effect of Spindle Diameter and Spindle Working Period on the Properties of 100% Viscose MVS Yarns

Abstract

This study focuses on the effects of various spindle diameters and the spindle working period on the properties of 100% viscose MVS yarns. MVS yarn samples produced with four levels of spindle diameter, 1. 1, 1. 2, 1.3, 1.4 mm and five levels of the spindle working period: 0, 1, 2, 3, 4 month, were evaluated on the basis of unevenness, hairiness, elongation at break, tenacity and work-of-break (B-work) values. The results indicate that a large spindle diameter results in high hairiness, as well as low unevenness and tenacity values. The wear of the spindle increases with an increasing working period. The wear is mainly seen in two different zones: the proximal edge of the hole entrance (tip zone), and the hole surface of spindles. After a four month working period, spindle wear becomes a more critical factor for 100% viscose MVS yarns.

Key words: MVS yarn, spindle wear, viscose yarn, spindle diameter.

■ Introduction

Murata Vortex Spinning (MVS), which is a successful commercial implementation of fasciated yarn technology, was devel­oped by Murata Machinery Company in Japan. This relatively new technology has significant advantages over ring, open-end and air jet spinning systems. One of the great advantages of MVS is that it is capable of producing yarns at speeds that are significantly higher than with any other system. Although the number of MVS frames operating in mills is still low, MVS installations are growing rap­idly [1].

Up until now, limited studies have been carried out by researchers to establish

gation (Figure 1). Therefore, the upper portions of some fibers are separated from the nip point between the front roll­ers; however, they are kept “open”. After the fibers have passed through the orifice, the upper portions of the fibers begin to expand due to the whirling force of the air jet stream and twine over the hollow stationary spindle. The fibers twined over the spindle are whirled around the fiber core and made into MVS yarn as they are drawn into the hollow spindle. The fin­ished yarn is wound onto a package after its defects have been removed [6].

a process-structure-property model for MVS yarns which can be used to optimise and improve MVS technology [2 - 5]. In an effort to supply additional information about the effects of process parameters on the properties of MVS yarns, we have undertaken this study.

■ Principle of yarn formation

In the MVS system a finisher sliver is supplied directly to a four roller/apron drafting unit. After coming out of the front rollers, the fibres approach the air-jet nozzle and are twisted by the force of the airjet stream. This twist motion tends to flow upwards. At this point a bending action at the needle tip, protrudes from the orifice, prevents this upward propa-

Figure 3. SEM images of spindle wear versus spindle working period for different spindle diameters.

■ Materials and test method

Three drawing passages were given to the carded slivers to produce a finisher sliver of 3.58 ktex. All the yarn samples, which had a linear density of 20 tex (Ne 30/1), were spun with the following spin­ning conditions: a 70° nozzle discharge angle, a delivery speed of 350 m/min , an air pressure of 0.5 MPa, 43-43-49 mm top roller gauges, and 43-43-44.5 mm bottom roller gauges, on a MVS 851 vor­tex spinner.

A list of the experimental spinning condi­tions is given in Table 1. Spindle diam­eter values were determined according to the limitation dictated by the instruction manual for the MVS 851 [6]. The work­ing periods of the spindle were chosen according to manufacturing experience. Three baby cones of about 150 g each were prepared under each experimental condition.

The effects of the spindle diameter and spindle working period on the proper­ties of 100% viscose MVS yarns were investigated on the basis of yarn uneven­ness (CVm %), hairiness, elongation at break, tenacity and work-of-break (B-work) values. Yarn samples were tested

same letters are not different from each other at a significance level of 0.05.

In addition to the physical tests of the yarns, the wear of the spindles were ex­amined under a LEO 440 model scanning electron microscope (SEM).

■ Results and discussion

Table 2 summarises the unevenness and hairiness properties of MVS yarns pro­duced with different spindle diameters and different spindle working periods.

for unevenness and hairiness on an Uster Tester 3, and for elongation, tenacity in cN/tex and B-work values on an Uster Tensojet. Yarn hairiness tests were also performed on a Zweigle G566 Hairi­ness Tester. We analysed the test results for significant differences using two-way replicated ANOVA, and the means were compared by conducting Student­Newman-Keuls (SNK) tests at a level of 0.05 using a Costat statistical pack­age. In the interpretation of SNK results, abbreviations a, b, c, d, and e represent factor level; factor levels that have the

According to ANOVA results, the spindle diameter and spindle working period and the combination of these two factors had a significant effect on the unevenness and hairiness properties of the MVS yarns. Figure 2 shows the results of yarn un­evenness measurements. From the SNK test results (Table 2) there were no signif­icant differences between the mean un­evenness values of MVS yarns produced with spindles of 1.1 mm and 1.2 mm diameter. Similar results were observed between unevenness properties of yarns produced with spindles of 1.3 mm and 1.4 mm diameter. However, there were significant differences between the un­evenness results for these two groups (1.1, 1.2 mm and 1.3, 1.4 mm). A decrease in spindle diameter from 1.3 mm to 1.2 mm resulted in a significant increase in the yarn unevenness value. A possible expla­nation for such unevenness properties is that fibers have more freedom to arrange themselves with a large spindle diameter.

The generation of spindle wear depends on the working period for different

spindle diameters, which are given in Figure 3. As the spindle working period increases, spindle wear also increases. Spindle wear was specially observed in two different zones: the hole surface and tip zone of the spindles, as shown in Figures 4 and 5, respectively. The SNK test results from Table 2 reveal that an increase in the spindle working period generally resulted in a significant in­crease in the yarn unevenness value. The highest unevenness values were obtained for MVS yarns produced with a spindle which has a 4 month working period. The possible reason for the higher unevenness values of MVS yarns produced with a spindle that has a longer working period is the deterioration effect of spindle wear on yarn formation.

With regard to yarn hairiness, the MVS yarns were tested on both the Uster Tes­ter 3 and the Zweigle G566 hairiness tester. We determined yarn hairiness in terms of the number of hairs in the 1 mm class, 2 mm class, S3 values, which rep-

resent the total number of hairy ends that rise from 3 to 25 mm for the yarn surface and Uster Hairiness Index. The SNK test results from Table 2 reveal that a small spindle diameter resulted in low hairi­ness values. The fiber bundle has more freedom to move inside a spindle of large diameter. Hence some twist is lost, wrap­pings become looser and yarn gets hairier. An increase in the spindle working period generally resulted in higher hairiness val­ues in terms of the Uster hairiness index. This trend is not clear for other hairiness values. Figure 6 shows the test results of yarn hairiness in terms of the Uster hairi­ness index.

Figures 7 and 8 show the tenacity and elongation at break results of the MVS yarns versus the spindle working period for different spindle diameters. Based on the ANOVA results, the spindle working period, spindle diameter and a combina­tion of these two factors have a signifi­cant effect on the tenacity, elongation at break and B-work values of MVS yarns.

Spindle wear is a major problem as it negatively affects MVS yarn properties. Spindle wear mainly occurs in the tip zone and the hole surface of the spindle. After a 4th month working period, the negative effetcs of spindle wear becomes more critical with respect to the uneven­ness, hairiness, tenacity and elongation properties of MVS yarns. The wear re­sults put forward in this study are valid only for this particular case, and may be different for other types of fiber.

As seen in Table 3, there were no signifi­cant differences between the mechanical properties of MVS yarns produced with spindles of 1.1 mm and 1.2 mm diameter. The lowest tenacity, elongation at break and B-work values were obtained for those produced with a spindle of 1.4 mm diameter (Table 3). This is mainly due to higher friction between fibers within the yarns, which were produced with smaller spindle diameters. Since a small spindle diameter gives less freedom to the fiber bundle to expand as it enters the spindle, higher friction occurs between fibers and results in tighter wrappings, higher twist and in turn denser yarns.

Even though there were no significant differences between the mean tenac­ity values of MVS yarns produced with spindles of 1.1 mm, 1.2 mm and 1.3 mm diameter. The mean elongation at break and B-work values of yarns produced with spindles of 1.3 mm diameter were higher than those of yarns produced with all other spindle diameters (Table 3).

The tenacity, elongation at break and B-work values of MVS yarns produced with a spindle that has a 4 month working period are significantly lower than those of yarns produced with spindles which have other working periods. Spindle wear mainly occurs after a three month working period (Figures 3, 4, 5). After a 4 month working period it is probable

that wear occurred in the tip zone. Fur­thermore, the hole surface of the spindle negatively affects the arrangement of fibers and resulted in a greater decrease in the mechanical properties of the MVS yarns.

■ Conclusions

Our findings show that various properties of MVS yarns are significantly affected by the spindle diameter and spindle working period.

Using larger spindle diameters results in higher hairiness values. Since the fiber bundle has more freedom to move inside a spindle with a large spindle diameter, wrappings become looser and yarn be­comes more hairy. With spindle diam­eters of 1.3 and 1.4 mm, lower uneven­ness values were obtained compared to spindle diameters of 1.1 and 1.2 mm.

The spindle diameter determines the tightness of the wrapper fibers. With a spindle diameter of 1.4 mm, relatively lower friction occurs between fibers and results in lower tenacity values. The best elongation at break values were obtained for MVS yarns produced with 1.3 mm spindle diameters. The choice of spindle diameter depends on not only yarn count and raw material, but also on the end-use properties of MVS yarns.

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Impacts on the Turkish Cotton Spinning Industry

Analysis of Global Impacts on the Turkish Cotton Spinning Industry

Abstract

In this study, the trends and impacts of global issues on the Turkish cotton spinning industry were identified based on data regarding installed capacities, total production, as well as manufacturing costs and foreign trade over a wide period, and the competitive position of the industry was analysed on the basis of export and import data in relation to its major rivals. In this way, it was aimed at exploring the current status and future prospects of the Turkish cotton spinning industry on the global market.

Key words: cotton spinning, Turkey, globalisation, competitiveness, comparative advantage.

■ Introduction

With a total production of almost 39 million tons, spun yarns dominate the world yarn market; they are used in a wide range of textile and apparel prod­ucts. Despite the fact that synthetic fibres have had a high growth rate in global fi­bre consumption since the beginning of the 1990s (see Figure 1), cotton is the leading fibre used in the world spun yarn industry (see Figure 2), with a share of 59%, which is followed by polyester, ac­counting for 26% [1].

Being the 4th biggest cotton consumer and ^7th biggest cotton producer in the world, with a yearly production capacity of almost 900 thousand tons, Turkey is ranked as the 5th largest among interna­tional cotton yarn producers, therefore cotton is a strategically important raw material for yarn manufacturing in Tur­key; Turkish cotton yarn exports account for almost 2% of the total textile and ap-

parel clothing exports, and 0.5% of the total export [2, 3].

As a result of the shifting of manufac­turing to regions where costs are lower, emerging textile producers have of late achieved constant growth in the global market share in terms of yarn produc­tion as in the case of all other stages in the textile manufacturing chain. Turkey is one of the yarn manufacturers that has faced many challenges and suffered from growing imports, particularly from Asian countries. In the following parts of the paper, the impacts of such a challenging environment on the Turkish cotton spin­ning industry, with an assessment of its competitive position, are exposed.

Installed capacities and total production

The high amount of state incentives allo­cated to the textile industry in the 1990s resulted in a capacity increase, which was preparation for the accession of Tur­key to the Customs Union. After the Cus­toms Union agreement came into force in 1996, Turkey’s export to the European Union increased steadily, and sector in­vestments accelerated as a result of the fact that Turkey gained a competitive

advantage in the EU market. Other rea­sons beyond the growth in investments were the expectation of an increase in domestic demand due to import quo­tas from countries outside the European Union within the scope of the Customs Union agreement and the beginning of cotton planting in South-eastern Anato­lia, which offers favourable conditions for cotton growing. Apart from a slight decrease in installed capacities in 1999 as a result of the 1998 financial crisis in Russia and Asia, the Turkish cotton spin­ning industry has continued to invest in new machinery to the present. However, it is worth mentioning that investments in recent years have actually been, to a large extent, modernisation investments. According to 2006 figures, Turkey ranks 5th in the amount of short staple spindles installed in the world with a total capac­ity of 6,500,000. Following China, with a total installed open-end rotor capac­ity of 1,840,000, Turkey ranks 2rd in the total installed open-end rotor capacity in the world, with a total of 577,000 ro­tors. The total number of installed short staple spindles and open-end rotors, and the total cotton yarn production in Tur­key are displayed in Table 1 (see page 8) in years. The average number of active units for both systems is also included in

the table as a percentage of the total in­stalled units [5, 6].

In conjunction with the increase in in­stalled capacities in the 1990s, cotton yarn production rose with an average an­nual rate of almost 7.3% within the same period. Right after a marked decrease in 2001 due to the effect of the financial cri­sis in November 2000, as a contraction in domestic demand, the total cotton yarn production in Turkey reached an aver­age amount of approximately 1,230,000 tons in the following years with slight changes. Despite the increasing installed capacity in the past few years, the rela­tively stable production can be mainly ascribed to high input costs, an overval­ued Turkish Lira and, hence, an increase in imports [7].

■ Manufacturing costs

Table 2 shows the total manufacturing costs of ring and open-end rotor spun yarns for seven important cotton yarn manufacturers in the world. The most im­portant component in the cost of cotton yarn manufacturing is that of raw mate­rial, with an average percentage of 50.9 for ring spun yarn, and 69.1 for open-end rotor spun yarn for the group of countries considered. With regard to both ring and open-end rotor spun yarn manufactur­ing costs, Turkey has the second lowest cost percentage (excluding raw material costs) after China, as shown in Tables 2 and 3. On the other hand, the percentage of raw material costs in the total cost of both ring and open-end rotor spun yarns is significantly high in Turkey. As regards capital costs, which is the second high­est component in the total manufacturing cost, Turkey is the most advantageous country. Despite the fact that profits vary across countries, Turkey’s difficulties in competing with respect to price should be evaluated by referring to the high raw

material and power costs, and subse­quently to the labour costs.

Whilst China has the advantage in terms of labour cost, its total yarn manufactur­ing cost is higher than most of the impor­tant yarn manufacturing countries in the world. The cost of ring spun yarn manu­facturing in Turkey is below the average, and Turkey seems to remain competitive with regard to the total cost of ring yarn manufacturing. On the other hand, the cost of open-end rotor spun yarn manu­facturing in Turkey is above the average of the seven countries mentioned. As can be seen from Figure 3, India is the most competitive manufacturer in terms of to­tal yarn manufacturing costs in the world and is the leading country in the import of cotton yarn to Turkey, with a weight of 57,512,323 kg [9].

■ Foreign trade

The data used in the present study were gathered from the Commodity Trade Sta­tistics Database of the United Nations Statistics Division. According to SITC Rev 3, subgroup 651.3 - Cotton yarn, other than sewing thread, was included in the analysis with the following basic headings:

651.31 - containing 85% or more by weight of cotton, put up for re­tail sale

651.32 - other, put up for retail sale 651.33 - containing 85% or more by

weight of cotton, not put up for

retail sale

651.34 - containing less than 85% by weight of cotton, not put up for retail sale

Export and import quantities of the Turk­ish cotton spinning industry between 1985 and 2007 are shown in Figure 4. Cotton yarn import was considerably low until 1990, while in the same period, the export rate was comparatively high as a

consequence of export oriented indus­trialisation policies based on free mar­ket economics. By 1990, exports had decreased despite a marked increase in cotton yarn production, whilst imports began to increase. The considerable de­valuation of the Turkish Lira and the con­traction in domestic demand resulted in a marked increase in exports in 1994, but decreased immediately after by almost 46%. However, with accelerated pro­duction after 1995, positively reflected in Turkey’s cotton yarn export, the in­dustry recorded a foreign trade surplus until 2002. The most striking aspect of the period after 2002 up to the present is the outstanding increase in cotton yarn imports, which indicates the transition of the Turkish textile and, particularly, clothing industry into an import based manufacturing structure [7, 9].

The increase in cotton yarn imports be­tween 2003 and 2007 has caused domes­tic cotton yarn manufacturers to be una­ble to compete under these circumstances and has consequently forced the govern­ment to take precautions against an un­fair competitive environment. For this reason in order to ensure to remove the severe loss and severe loss threat of the increase in imports and import conditions on domestic production, a supplementary financial obligation on cotton yarn im­ports was put into force by decision of the Council of Ministers as a safeguard measure on October 21 st_, 2008 The prod­uct, subject to application, is classified under the Customs sub-headings given below, within the Turkish Customs Tariff Schedule:

52.05 Cotton Yarn (other than sewing thread), containing 85 % or more by weight of cotton, not put up for retail sale.

52.06 Cotton Yarn (other than sewing thread), containing less than 85 % by weight of cotton, not put up for retail sale.

52.07 Cotton Yarn (other than sewing
thread) put up for retail sale.

According to the decision of the Coun­cil of Ministers, until 14.7.2009, a 20% supplementary financial obligation, 19% and 18% for the following two years, will be collected: no more than 1 USD/kg, 0.95 USD/kg, and 0.90 USD/kg, and no lower than 0.35 USD/kg, 0.33 USD/kg and 0.31 USD/kg, respectively [10].

Competitiveness of the industry

The competitiveness of the Turkish cot­ton spinning industry in comparison with major manufacturers was analysed by applying the Revealed Compara­tive Advantage (RCA) index developed by Balassa, which is also known as the Balassa index, and Vollrath’s measures of competitiveness, which include the rela­tive export advantage index (RXA), the relative import advantage index (RMA), the relative trade advantage index (RTA) and the relative competitiveness index (RC). They are calculated by using the following formulas [1 1]:

Vollrath’s relative export advantage in­dex (RXA) differs from the Ballasa index by allowing one to distinguish between a specific commodity/country and the rest of the commodities/countries. The indi­ces developed by Vollrath eliminate the country and commodity double counting in world trade [11 - 13]. Using the data gathered from the Commodity Trade Sta­tistics Database of the United Nations Statistics Division regarding subgroup 651.3, RCA, RXA, RTA and RC indices were calculated, the results of which are given in Tables 3 - 6.

Table 3. Balassa’s revealed comparative advantage indices (RCA).

Country                      2000              2001               2002        2003              2004        2005        2006       2007

Turkey                  8.25         7.91         4.66         4.55         5.00         4.32         3.73          2.77

Pakistan               107.47           100.47     84.56       74.48       87.43       93.20       107.60  113.82

India                    27.21       22.71       20.64       18.22       15.30       17.31       16.45      17.77

Indonesia                        4.17         4.63         4.21         4.62         5.52         4.19         4.19          3.72

China                   2.25         2.41         2.78         2.83         2.41         2.24         2.36          2.28

Italy                                   1.69         1.55         1.43         1.32         1.30         1.26         1.20         1.21

USA                     0.33         0.33         0.40         0.56         0.71                0.80         0.90          1.07

Rep. of Korea      0.68         0.69         0.64         0.48         0.47         0.48         0.35          0.38

Brasil                    0.81                0.61         0.98         1.27         0.86         0.63         0.51          0.27

Table 4. Vollrath’s relative export advantage indices (RXA).

Country                      2000              2001               2002        2003              2004        2005        2006       2007

Turkey                  8.57         8.24         4.72         4.66         5.15         4.42         3.80         2.81

Pakistan               141.96     130.82     105.45     90.63       107.42     115.76     136.26      142.35

India                    33.83       27.16       24.70       21.39       17.50       20.61       19.58      21.47

Indonesia                        4.31         4.79         4.34         4.76         5.71                4.31         4.31         3.81

China                   2.36         2.56         3.04         3.16         2.64         2.45         2.65          2.57

Italy                                   1.73         1.58         1.45         1.34         1.31                1.27         1.21         1.21

USA                     0.31                0.30         0.37         0.54         0.69         0.78         0.90          1.08

Rep. of Korea      0.67         0.69         0.63         0.47         0.46         0.47         0.34          0.37

Brasil                    0.81                0.61         0.84         1.28         0.86         0.62         0.51          0.27

 

 

Table 5. Vollrath’s relative trade advantage indices (RTA).

Country                     2000              2001               2002        2003              2004        2005        2006       2007

Turkey                 6.54         6.31         2.24         1.13         2.13         1.25         1.15         -2.29

Pakistan              141.96     130.82     105.43     90.47       106.61     115.13     135.78     142.01

India                    33.70       27.03       24.54       21.30       17.42       20.49       19.41           21.29

Indonesia                       2.65         3.17         2.77         3.25         4.39         3.16         3.28         2.71

China                   -2.23        -2.31        -1.91        -1.07        -0.87        -1.65        -1.76        -1.57

Italy                     -0.26        -0.38        -0.36        -0.51        -0.28        -0.38        -0.74        -0.74

USA                     0.01                0.06         0.13         0.30         0.38         0.51         0.63          0.90

Rep. of Korea      -2.69        -2.97        -2.84        -2.37        -2.35        -2.12        -2.56        -2.15

Brasil                   0.39         0.44         0.71         1.16         0.64         0.25         0.16         -0.59

Table 6. Vollrath’s revealed competitiveness indices (RC).

Country                           2000        2001               2002               2003        2004        2005        2006       2007

Turkey                     1.44         1.45         0.65         0.28         0.53         0.33         0.36        -0.60

Pakistan                  10.60       12.71              8.49         6.32         4.89         5.21                5.65         6.02

India                        5.55         5.34         5.02         5.53         5.38         5.19         4.71         4.79

Indonesia                             0.96         1.09         1.02         1.15         1.46         1.33         1.43         1.25

China                      -0.67        -0.64        -0.49        -0.29        -0.29        -0.52        -0.51       -0.48

Italy                         -0.14        -0.22        -0.22        -0.33        -0.19        -0.26        -0.48       -0.48

USA                        0.02         0.20         0.44         0.80         0.80         1.06         1.23         1.81

Rep. of Korea          -1.61        -1.67        -1.71        -1.80        -1.81        -1.71        -2.15       -1.92

Brasil                       0.66         1.30         1.91                2.40         1.40         0.50         0.38        -1.16

The analysis of Turkey’s comparative ad­vantage in cotton yarn on the basis of the Balassa index showed that this advantage decreased over the period between 2000 and 2007. The results in Table 3 show that the revealed comparative advantage for Pakistan and India are greater than for Turkey for the entire period considered. Actually, a decreasing trend in compara­tive advantage can be observed for the majority of the countries, apart from Pakistan, India and the USA, in the past few years, indicating that the percentage of cotton yarn exports in the total exports of the countries stated has increased on the value basis.

According to Vollrath, the positive val­ues of the indices indicate a compara­tive advantage, whereas negative values indicate a comparative disadvantage [11 - 13]. As in the case of the revealed comparative advantage, Turkey has a decreasing relative export advantage in the cotton spinning industry. Turkey’s relative trade advantage indices within the period of 2000 - 2007 verified the in­crease in the import rate and indicated a relative disadvantage existing by the year 2007. Similarly, Vollrath’s revealed com­petitiveness index (RC) for Turkey also showed a decreasing trend from 2000, turning into a competitive disadvantage in 2007.

The results of the analysis identified that among the cotton yarn exporting coun­tries, Pakistan has the highest relative export and trade advantage, and revealed competitiveness. The variations in the competitive position with respect to all types of indices across the years means that the cotton spinning industry in Tur­key has been affected in a negative man­ner by intensified price based competi­tion on the global market.

■ Discussion and conclusion

The competitive power of the Turkish textile and clothing industry is based on the fact that Turkey is an important cot­ton producer, and it has well-developed sub-sectors with advanced technology and infrastructure throughout all the stag­es in the textile and clothing manufactur­ing chain. Therefore, it is inevitable for the cotton spinning industry to become more competitive in the upcoming years. However, most of the manufacturers in Turkey have recently stopped produc-

tion, with some factories having been closed down.

The negative course experienced in the Turkish cotton spinning industry in recent years with regard to both domestic and foreign markets has been mainly caused by the high rate of import penetration due to challenging competition arising as a consequence of world trade liberalisation as well as high input costs and an over-

valued Turkish Lira. Due to subsidies in yarn manufacturing in rival countries, as well as low manufacturing costs, unit im­port prices have been steadily decreasing, and therefore, as an intermediate product, the import of cotton yarn has increased in recent years; in 2007, imports of cot­ton yarn increased dramatically by 102%, reaching 503,479,029 USD in Turkey. Besides, an overvalued Turkish Lira and low tax rates on imported inputs that are

subject to export according to the inward processing regime are also highlighted as important factors behind the surge in cot­ton yarn imports [14, 15].

The relocation of production in regions where labour costs are low has been widely accepted as a survival solution against the effects of the liberalisation of world trade; however, yarn manufac­turing is a capital intensive industry, and strategies for yarn manufacturing should be constituted by considering not only la­bour costs but also raw material costs and availability, capital costs, power costs, as well as labour and machine productiv­ity. The weakness of Turkey in terms of the cost of cotton yarn manufacturing is caused mainly due to the high cost of raw material, which is followed by high pow­er and labour costs, respectively, when compared to top manufacturers. The most remarkable development designed to support domestic production has been the supplementary financial obligation on cotton yarn imports that was put into force in October 2008 for a period of three years. However, the lowering of manufacturing costs is strongly needed in order to achieve a continuous advan­tage in terms of production. In addition, although recent investments are declared to be for modernisation, an increase in installed capacity as opposed to a stable production rate and considerable increase in imports would appear to be an inap­propriate approach to enhance competi­tive power.

In conclusion, the analysis based on foreign trade data of the Turkish cotton spinning industry has highlighted that the comparative advantage and competi­tiveness of the industry has exhibited a gradually decreasing pattern, even turn­ing into a disadvantage by 2007. Enhanc­ing the competitiveness of the Turkish cotton spinning industry is unavoidable in order to that the Turkish textile and clothing industry become competitive once again as a whole on a global scale. However, in view of the current circum­stances, focusing on the development and production of high value added, customer oriented goods should be the priority in order to gain a competitive advantage, since competing in low value added standard bulk products is getting difficult and even impossible. Such an approach calls for target oriented investments and renovations for enabling finer, high qual­ity, innovative and specialised yarn pro­duction by considering the advancements

being made in spinning technology, deep research and development competencies and strategic partnership alliances. Fi­nally, government support through regu­lations, incentives and policies as well as the efforts of non-governmental organi­sations should be developed by consider­ing the interactions among all subsectors, aiming to reconstruct the Turkish textile and clothing industry entirely.

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