Mechanical crimp texturizing of non-thermoplastic viscose rayon yarn

Abstract

There are technological limitations in the processing of smooth, slippery and rather flat multifilament viscose rayon yarn. The present work describes a shorter route for viscose rayon modification through mechanical crimp texturizing. Texturizing was performed with different pre-twists and optimized texturizing twist. This work describes a shorter and cost effective route for viscose rayon modification through mechanical crimp texturizing. The prepared texturized viscose rayon yarn has achieved the desirable structural characteristics of spun yarn as depicted in SEM micrographs. The textured yarn has retained an almost identical fineness with the parent yarn. Unlike air jet texturizing, mechanical crimp texturizing has benefits in terms of retro-processing of costlier viscose rayon yarn. Although it was textured, it has not shown any significant drop in tenacity and, apart from that, shows enhanced the elongation property compared to the parent yarn.

Keywords

mechanical crimp texturizing viscose rayon pre-twist instability mechanical properties

Viscose Rayon is the first regenerated natural (cellulose) based man-made fibre. It possesses desirable properties of cotton, like good moisture absorbency, breathability and comfort to wear and can also be easily dyed in vivid colors. So it is thought to be the most suitable replacement for cotton.^1–3 However, unlike cotton it possesses remarkably low dry and wet strength. It possesses smooth slippery structure with a high degree of cohesion. This creates handling problems of the material during shop floor production. Therefore it needs to undergo structural modifications before being used for commercial fabric manufacturing process.^1,3–7

Two commercialized options are available to attain required transformation of flat, weak, smooth and slippery structure into stronger, rugged and bulky structure. The first option is a short staple spinning of viscose rayon fibres, either as one hundred percent or in a blend. But this involves a longer route of production due to multistep processing.^1–4,6 Thereby it adds to production cost and time. The second option is the direct use of highly twisted viscose rayon yarn in weaving. Here the production route is quite short but sacrifices favorable characteristics of viscose rayon, viz., softness, feel, comfort and bulk.^6,7

Texturizing of viscose filament yarn should be the third possible option, but it is still not commercialized. Ivanova et al.^4,5 made the first attempt in this direction. They produced a textured bulky viscose rayon yarn based on the principle of false twisting by the following multistep process. Considering the non-thermo plasticity of viscose rayon, in the first step, the viscose rayon in the cellulose xanthate state was twisted, before completion of regeneration process. In the second step, the resulting deformation of the filaments of the coagulated but not fully regenerated yarn was set during the final decomposition of the xanthate. In subsequent steps the yarn was made to undergo a finishing and drying processes. Such a dried yarn was then twisted in the opposite direction in the final step. The torque induced during this course forced the filaments to revert to the state of equilibrium, but the elastic forces caused them to assume the configuration of coil springs and form a bulky structure. Although successful, this complicated multistep processing imposes technological as well as economical limitations in its commercialization. However, the efforts of Ivanova et al. have enlightened the importance of the bulky structure of this man-made yarn with good hygroscopic properties. This leads to the challenge to develop a single step texturizing technique to overcome all such techno-economical limitations.

False-twist texturizing and air jet texturizing are the commercially successful techniques in today’s context. Both of them are single step processes. Economically their proficiency is said to be better than the technique suggested by Ivanova et al.^4,5 Technically, the false-twist texturizing technique can not be preferred for non-thermoplastic viscose rayon yarn as it is based on the concept of the heat setting of the deformation.^1,7–9 On the contrary, mechanical mode air jet texturizing can be comfortably used for non-thermoplastic viscose. However use of costly compressed air and installation as well as maintenance of the compressor unit adds to product cost. Apart from this, a coarser product is obtained from over fed fine feeder yarn, which is costly. This adversely affects the product cost. The clinging effect of loopy yarn also makes post treatments like twisting or stabilizing followed by heat setting compulsory.^1,2,8 Deviation of filaments from yarn axis for loop formation makes textured yarn weaker than parent yarn. This becomes significant in case of an originally weaker parent yarn. Even well-anchored loops with a yarn core reduce breaking extension, which is not preferable.^10–14 All these factors have imposed restrictions on the implementation of a technique for viscose rayon, which could otherwise be feasible.

Mechanical crimp texturizing

The mechanical crimp texturizing concept was introduced by Shaikh et al.,^15–18 by linking concepts of false-twist texturizing and air jet texturizing. This technique is still at the experimental stage. Its basic concept and the outcome of research done on polyester and nylon have been briefly reviewed.^15–18

Basic concept

Pre-twisted FDY (Fully Drawn Yarn) flat multifilament yarn is subjected to higher false twisting (depending on yarn fineness) action under the condition of underfeeding (depending on the ductility of parent yarn). The torque caused due to the high level of false twisting forces the filaments to follow a helical path at a certain angle (dependent on the magnitude of twist and denier per filament) to the longitudinal axis of the filament yarn. Internal stresses arising in single filaments tend to bend the filament and take the shape of a spatial helical spring. After the yarn has passed through the false-twisting unit, the initial twist reasserts itself and locks the already formed crimpy convolutions in position.

The crimpy constituent filaments locked together by real twist and intermingling had shown a good similarity with the ring spun yarn. Even mechanical crimp textured polyester yarns were used successfully as weft on loom and as feeder yarn on knitting machine without any need of post twisting or treatment and did not show any clinging tendency with machine parts.¹⁸

Improved orientation on under feeding and added binding forces due to the presence of real twist in the structure had retained almost identical tenacity of the textured yarns to that of their respective parent yarns.^16,18 The linear density of textured yarn is found to be same as that of the parent yarn, which is due to combined effect of pre-twisting, crimping and under feeding.^15,18 Comparative cost analysis of three texturizing systems had put this mechanical concept next to cheaper false-twist texturizing due to obviation of cost adding factors.¹⁸ Altogether it makes this newly engineered concept easy and cost effective for throwsters. The present research work represents such an effort. It deals with the evaluation of technical efficacy of this innovative system in texturizing non-thermoplastic viscose rayon yarn.

Experimental details

Materials

Fully drawn white 300-denier (270 dtex)/76-fils. viscose rayon multifilament yarn used as the parent yarn for the present study.

Methodology

The selected parent yarn was textured on the mechanical crimp texturizing apparatus. Texturizing was carried out in each division with optimum processing conditions by varying only the pre-twist. Three pre-twist levels were used, viz., 157 tpm, 315 tpm and 472 tpm. The selected pre-twist values were guided by previous work on mechanical bulking by Sen et al.¹⁹ The process parameters adopted for mechanical crimp texturizing of viscose rayon yarn are given below. They were optimized experimentally.

Input parent yarn tension = 0.500 gf/tex

Bulking zone length = 25 mm

Under feed = 10%

Delivery speed = 150 m/min

Winding tension = 0.470 gf/tex

Optimization of process variables

The process variables, like bulking zone length, input yarn tension and underfeed, have been optimized for the selected 300-denier/76-fils. viscose rayon multifilament parent. The pattern of study in the pilot trials is similar to that adopted for the polyester yarn in the earlier study.¹⁶ A brief review of trials along with their outcome has been given.

In the first phase of the experiment, pilot trials were conducted with a 300-denier/76-fils., viscose rayon multifilament parent yarn by varying only bulking-zone length from a minimum possible 25 mm to a maximum possible 100 mm. Bulking-zone length was varied in regular increments of 25 mm during the experiment. Below 25 mm bulking zone length, frequent end breakages were recorded due to high tension, whereas going beyond 100 mm resulted in frequent end-breakage due to the bulging of long unsupported length at a higher false twist. Going in similar findings as Sen et al.¹⁹ for mechanical bulking in earlier experiments on polyester,¹⁶ suggested that better textured product was obtained shorter bulking zone length, i.e. 25 mm. This behavior is attributed to the favorable bending stress and torsional stress undergone by constituent filaments at the applied identical false twist in the shorter bulking zone length.

In second phase of experiments texturizing was carried out by varying only the input parent yarn tension value at the optimum bulking-zone length. Input yarn tension was varied between 0.45 gf/tex to 0.81 gf/tex and measured with mechanical tensiometer. The best texturizing effects have been observed at an input tension of 0.500 gf/tex. A remarkable rise in end breaks was observed due to balloon formation at low tension and filament fraying at high tension. This has shown close agreement with the empirically derived optimum input yarn tension value for twisting multifilament viscose rayon yarn by Hearle et al.²⁰ They found a 0.45 gf/tex input tension value most suitable for twisting viscose rayon yarn. Intensity of migration get reduced if twisting is carried out beyond this set tension limit. The quality of the textured yarn will be poor at a low intensity of migration.^16–18

The underfeed is mainly influenced by ductility and mechanical properties of the input yarn. It maintains a constant texturizing tension of 0.500 gf/tex at bulking zone based on constant extension principle.⁸ This was set by changing the gears in the main drive.¹⁸ Winding was carried out at 5% over feed.

Optimum false-twist for selected viscose rayon yarn was derived in a similar fashion that has been followed for polyester.¹⁶ The minimum false-twist employed was calculated as per Heberlein’s advanced empirical formula (Equation 1).^12,21 This was based on similarity found in crimping methodology for both the systems. However, ‘K’ can differ from the calculated value due to elimination of heat in the present technique.

K = 800 + \frac{2, 75, 000}{D + 60}

(1)

Where, K = optimum twist (tpm)

D = yarn fineness (denier)

Minimum false-twist was then increased gradually by a uniform increment of 20 tpm until it resulted in the breakage of constituent filaments. The interval was kept narrower than for polyester due to the difference between materials in chemical constituents and strength. The false-twist value where filament rupture begins was recorded as highest false-twist for the yarn under consideration. Rupturing of constituent fibers/filaments began on twisting the yarn beyond its optimum twist level due to the obliquity effect.^1,22 The preferable optimum false-twist level K (tpm) was regarded as the highest possible false-twist at which constituent filaments of parent yarn attained maximum possible crimp without getting damaged/ruptured. These empirically derived optimum twist values, given in Table 1, were used for texturizing.

Table 1.

Experimental design

Sample code	Parent yarn specifications	Pre-twisttpm (tpi)	Optimum false-twist K (tpm (tpi))
A₁	300/76 fils., white, multilob	157 (4)	1573 (40)
A₂		315 (8)	1889 (48)
A₃		472 (12)	2321 (59)

Test methods

Textured yarns were tested for their percent bulk, percent instability, percent boiling water shrinkage and mechanical properties after conditioning for 24 hours at standard atmospheric conditions for tropical regions.²³ Parent yarn was also checked for denier, mechanical properties, long term regularity and boiling water shrinkage after conditioning. The structural changes in the flat filament yarn on texturizing were observed on a Scanning Electron Microscope (SEM) instrument (model JSM5610LV, version 1.0, Jeol, Japan) using Oxford-Inca software (U.K.). SEM micrographs were obtained at the set up of 15 kv, 35 × , 500 µm for the same. The Erma scope has been used to measure structural characteristics at 100 × magnification.

Long-term regularity of product yarn was confirmed from the subjective evaluation for 100 m wrappings. Samples were prepared from top-layer, middle-layer and bottom-layer of one of the randomly picked bobbin out of five produced. A total of 50 yarn samples, each of 1 m were selected at random from different layers of the five bobbins for the measurement of structural characteristics and uniformity of texturizing effect. Samples were observed under the Erma scope microscope in continuous 2 mm section at 100 × magnification. The length of the section was limited by the field of the microscope’s focal length. Short-term irregularity of the parent as well as textured yarns was checked by Premier Evenness tester at the test speed of 100 m/min. An average of five readings for each sample has been considered for the study.

A skein of 90 m was weighed accurately by using Libror balance for measuring the denier of the parent yarn and textured yarn as per the BISFA method.²⁴ The mechanical properties were checked on Lloyd tensile tester using gauge length of 500 mm and cross-head speed of 100 mm/min as per ASTM standard D 2256-02.²⁵ Looking at the similarity with air jet textured yarn in imparting stability to the textured structure,^15–18 the DuPont method was used to measure the stability of curls.¹⁴ Burnip et al. introduced the concept of bulk factor (θ) for measuring the bulk of false-twist textured yarns.²⁶ Hence bulk is the outcome of crimp characteristics attained by flat yarn with mechanical crimp texturizing and false-twist texturizing. The same method was adopted for measuring the bulk of the newly engineered yarn.¹⁵ The percent boiling water shrinkage of parent and textured yarn was measured as per the BISFA method.²⁴

Results and discussion

Structural characteristics of textured yarn

Evaluation of structural characteristics of innovative yarn needs to be done before establishing the relationship between its structure and properties. So, structural changes undergone by low pre-twist textured yarn (sample A₁) with respect to its parent yarn has been analyzed from their SEM images (Figures 1(a) and (b)).

It can be observed that the straight rod like filaments of the parent yarn (Figure 1(a)) have bent to form coils of different sizes. The bending rigidity of the filament, degree of twist [twist angle] and the tension undergone by the filaments during twisting are the main decisive factors for the frequency and size of coils formed on mechanical crimp texturizing.^16–18 The bending rigidity of yarn is mainly influenced by its chemical constitution, fineness of filament and density.^{16–18,22,27,28} For the selected yarn and filament fineness, degree of twist and tension has played the decisive role in defining size and frequency of coils formed. Filament or yarn tension was maintained constant by means of additive tensioner at the entry to the bulking zone and the constant extension method (under feed) was used at the bulking zone. However, torque caused on twisting (false twist) adds to this tension.^28–31 In the absence of heat relaxation, the resultant tension undergone by individual filaments varies as per their radial position occupied during twisting. Filament on the yarn surface undergoes more tension in comparison to the filament at the centre and tends to migrate from surface to centre.^{24,25,29–35} Hence, bending of the filament on the surface is more than that at the centre. This alters the size of the coils formed. The coils are regularly disposed along the yarn axis as well as in the space around it due to the change in their radial position. Frequently changing the radial position of bent filaments from surface to centre and again back to the surface along the length of yarn results in intermingling of filaments in the yarn matrix (Figure 1(b)). This imparts stability to crimpy configurations attained against lateral forces. Distinct groups of surface curls of various configurations and dimensions are bound by real twist (pre-twist) to the core yarn, giving it a bulky, voluminous structure that has a very close resemblance to spun yarn. Microscopical views of randomly selected yarn from the packages (Figure 2), also substantiates this observation.

Figure 1.

SEM Micrographs of 300 d/76 fils. (a) parent and (b) mechanical crimp textured yarn [pre twist = 157 tpm].

Figure 2.

Microscopical views of 300 d/76 fils. mechanical crimp textured yarn (sample A₁) (snap shots taken at random location).

Texturizing was carried out at an optimum false-twist level for all the three samples under consideration. The pattern of coil formation, filament migration and intermingling has not shown any remarkable difference amongst them. However, the pre-twist value was increased from sample A₁ to sample A₃ with the regular increment of 4 tpi (Table 1). This has made the subsequent yarn compact (Figure 3) by going in accordance with the twisting behavior of viscose rayon multifilament yarn.^32–34

Figure 3.

Microscopical views of 300 d/76 fils. mechanical crimp textured yarns.

Figure 4.

Wrapping board of mechanical crimp textured yarn [sample A₁].

Structural characteristics like curls/m, average height of curl, core diameter and textured yarn diameter have been measured as per suggested for air jet textured yarn by Wray et al.^8,11 Inherent bulkiness of textured yarn is the outcome of these structural transformations. Therefore change in the voluminisity of the structure, viz., bulk factor, stability of the crimpy configuration, change in the linear density and boiling water shrinkage have been evaluated along with reference to the structural changes. All these measurements are summarized in Table 2.

Table 2.

Parents and textured yarn properties

Properties/Sample	Parent yarn	Textured yarn
Properties/Sample	Parent yarn	Sample A₁	Sample A₂	Sample A₃
Diameter(mm)	0.2750	0.7247	0.5431	0.4434
Bulk factor (θ)	--	7.10	3.90	2.60
Core diameter (mm)	--	0.2400	0.2340	0.2281
Curl height (mm)	--	0.2424	0.1545	0.1077
Curl frequency/m	--	4600	6800	7900
Curl instability (%)	--	2.40	1.60	1.02
Denier	300	^# F: 278	F: 284	F: 289
Denier	T: 293	T: 295	T: 298
Boiling water shrinkage (%)	1.3	^# F: 1.81	F: 2.98	F: 4.05
Boiling water shrinkage (%)	T: 2.80	T: 4.30	T: 6.20
Unevenness (%)	3.2	2.32	2.18	2.28

^#F = feeder yarn, T = textured yarn.

It can be observed that pre-twist level has a significant effect on textured viscose rayon yarn diameter, curl size, as well as curl frequency at an optimum false-twist level. This behavior has gone in accordance with the migration pattern observed during the twisting of multifilament yarn at different producer twist or initial twist levels.^{20,22,27,30–35} Accordingly, the yarn with higher initial twist has an increased number of filaments occupying different initial radial position along the length of yarn axis, to start with the migration on final twisting. This can lead towards increased total migration in the final yarn. Following the same classical twist theory, filaments that have undergone frequent changeover have not only enhanced curl frequency, but also reduced curl size. Increased migration along with higher pre-twist (real twist) in the structure has produced well-compacted textured yarn with a striking reduction in diameter (Table 2 and Figure 3).

Regularity

Figure 3 illustrates randomly selected snap shots for microscopical views of sample A₁ taken for long-term regularity evaluation. The occurrence of the regular crimpy effect has been observed.

Reduction in U% has been recorded for all the textured yarns as compared to the parent yarn. This is mainly attributed to the under feed given during texturizing.²⁶

Percent instability

Stability of the newly attained crimpy configuration is influenced by the extent of migration and magnitude of locking twist (pre-twist) in the structure. Both the parameters have shown an increase from sample A₁ to sample A₃ as mentioned in the previous section. These have subsequently bound the curls well with the textured yarn core (Figure 3) and offered higher resistance against permanent extension at an applied force. This is reflected in the reduced percent crimp instability with increased pre-twist level (Table 2). However, percent crimp instability measured for all the samples in consideration are well below the DuPont limit of 5%.¹⁴

Bulk factor

Bulk factor is the ratio of specific volume of textured yarn to that of flat yarn. Thus, for identical material type, yarn size and section length, it really represents the ratio of the square of the diameter of the textured yarn to that of the flat parent yarn.^15,26 Reduction in textured yarn diameter with increased pre-twist has reduced proportionately the bulk factor as per expectation (Table 2).

Denier

The linear density of the parent yarn has undergone changes as per the magnitude of attenuation and contraction employed during the course of texturizing. A constant extension mode has been adopted for maintaining constant yarn tension during texturizing (10% under feed, Section 3.2). Drawing action caused due to under feed has reduced yarn fineness to 269 denier (based on an average of 10 readings). Simultaneously, the parent yarn was pre-twisted before entering the bulking zone. This increases linear density in direct proportion to twist contraction. Crimpiness attained on texturizing further increases linear density in direct proportion to crimp contraction. Thus for the adopted direct yarn numbering system, viz. dtex, textured yarn fineness is equal to the algebraic sum of changes in fineness magnitudes undergone by the parent yarn. The coarsest denier measured for sample A₃, having the highest curl frequency as well as pre-twist at an identical under feed ratio, have substantiated this argument.

Percent boiling water shrinkage

Dimensional stability and cover of the fabric is mainly affected by the percent boiling water shrinkage value of the constituent yarns. It has a great influence on garment fit also.^8,10,12,36 Therefore more attention should be paid to the measure of percent boiling water shrinkage for the newly engineered yarn, especially designed for apparel.

Torsional deformation and bending deformation increase in direct proportion to amount of twist employed. The optimum false-twist value has increased along with the increase in pre-twist value (Table 1). Thus, the parent yarn has undergone highest stress when textured with higher pre-twist. The highest percent boiling water shrinkage obtained for sample A₃ substantiates this argument. The higher amount of stress involved during mechanical crimp texturizing and the absence of heat relaxation during the process has allowed the product to shrink more.^1,3,37 Gubaidullina³⁸ also found similar behavior for viscose rayon multifilament yarn while studying the influence of twist on its physico-mechanical properties. Going on the closer resemblance with these theories, percent boiling water shrinkage of the feeder yarn has also shown rise with the increase in pre-twist value (Table 2).

Mechanical properties

Mechanical properties of yarns are important for assessing their suitability for subsequent processes. Therefore, in depth analysis of the newly engineered product and its tensile behavior with respect to parent yarn is required. Hence, comparison of the stress–strain curves of the parent yarn (untextured) and textured viscose rayon yarns, given graphically in Figure 5, reveal striking differences.

Parent viscose rayon yarn tensile behavior During the tensile testing of parent yarn, all the filaments in a parent yarn simultaneously share the applied load to the yarn and are deformed elastically (Figure 5). When the load has increased beyond the elastic limit, all the filaments are plastically deformed, exhibiting an increasing strength. This continues up to the yield point after which it elongates rapidly. When the stress in an individual filament exceeds its breaking stress, it breaks, regardless of the other filaments’ condition. Therefore, in the parent yarn, the break has occurred in different filaments at different times, probably due to slight variations in their diameter, and some of the filaments appeared to elongate more than others for the zero twisted structure. Nevertheless, for the purpose of the strength tests, the load that causes most of the filaments to break is taken as the breaking load for the yarn and the corresponding elongation is regarded as the breaking elongation. These values are reported in terms of tenacity/stress (gpd) and percent extension/strain (%) in Table 3 as well as graphically (Figure 5).

Figure 5.

Stress–strain curves of parent yarn and mechanical crimp textured yarns A₁, A₂ and A₃.

Feeder viscose rayon yarn tensile behavior Feeder yarn refers to drawn and pre-twisted parent yarn. The behavior of feeder yarn against the applied tensile load is similar to that of the parent yarn in terms of initial elastic deformation followed by plastic deformation. The presence of real-twist in the yarn structure and drawing caused due to under feed differ in terms of breaking load and elongation values. Drawing action improves filament orientation and thereby increases breaking load value, but elongation diminishes in direct proportion to the amount of under feed.^1–3 On the contrary, twisting of filaments exerts lateral forces that increase the inter-filament friction, delay the rupture and thereby increase breaking loads as well as elongation.^4,38 The net effect of both the factors has resulted in increased stress but reduced strain of the feeder yarn as compared to its parent yarn (Table 3).

Table 3.

Mechanical properties of parent yarn and textured yarn

Sample code	Pre-twist (tpm)	Parent yarn		Feeder yarn		Textured yarn
Sample code	Pre-twist (tpm)	Tenacity (gpd)*	Extension (%)	Tenacity (gpd)*	Extension (%)	Tenacity (gpd) ^a	Extension (%)
A₁	157	2.04	24.60	2.25	21.88	1.95	34.38
A₂	315			2.53	20.45	2.00	32.60
A₃	472			2.66	18.96	1.87	27.50

gpd = grams per denier.

Textured viscose rayon yarn tensile behavior Textured viscose rayon yarns have exhibited totally different stress–strain characteristics from the parent yarn (Figure 5). They have shown lower tenacity but higher percentage extension than their respective feeder yarn (Table 3). This can be mainly attributed to its curled constituent filaments, randomly entangled (due to intermingling) and locked by the pre-twist at regular intervals. Deformation of textured yarn has increased with permanent elongation due to opening of the curls beyond the elastic limit of the applied load. Opening of the curls has shown rise in strain (%). However, locking of these curls through intermingling and use of real twist in the yarn matrix has resisted this opening of curls at an applied force. Resistance offered is greater with higher pre-twist and degree of intermingling. Hence, sample A₃ shows the lowest strain (%) value, although it contains the highest curl frequency (Table 3 and Figure 5).

All the filaments have exhibited entangled curls and twisted sections intermittently along their lengths. But these are separated by straight portions of filaments (Figure 2(b)). At any section of the yarn, at any particular instance, only these straight portions can resist the applied load effectively. Most likely such fewer load carrying straight filaments are left behind for the yarn textured with a higher pre-twist, sample A₃, due to its higher curl frequency (Table 2). So, a higher drop is likely in its tenacity value as compared to parent yarn amongst the group. However, increased cohesive forces due to higher pre-twist and extent of intermingling has stopped a further drop in its tenacity due to constituent filament diversity. Owing to the same resisting forces, sample A₃ does not show a marginal drop in breaking tenacity compared to parent yarn (Table 3).

The binding force of intermingling and pre-twisting has made all the textured yarns behave like one compact unit, unlike their parent yarn. This has increased their resistance against applied forces in direct proportion to binding force magnitude. Hence, higher stress values are executed by all the textured yarns compared to parent yarn before break, even though they have reached breaking point simultaneously due to one unit unlike the parent yarn, resulting in an almost instantaneous breakage of the textured yarn (Figure 5).

Conclusion

Fully drawn non-thermoplastic viscose rayon multifilament yarn was successfully textured by the mechanical crimp texturizing technique. Product yarn so obtained has been checked for its structural characteristics using SEM micrographs. The structure shows good resemblance with the preferable ring spun as well as air jet textured yarn structures. Increase in curl frequency but reduction in curl size is observed with the increased pre-twist in the textured yarn structure. The increased lateral force at higher pre-twist levels reduces curl instability. Long term and short-term regularities are tested. The wrapping boards have ascertained long-term uniformity of the texturizing effect. All the textured yarns have exhibited lower unevenness (U %) than that of the parent yarn due to axial stress induced because of under feed.

Although the yarns are textured, mechanical parameters of product yarns have shown the proficiency in sustaining the forthcoming stresses by retaining almost identical tenacity as that of the parent yarn. Identical fineness is retained by textured yarns similar to that of parent yarn due to the constant extension mode adopted for texturizing. The presence of real twist in the structure of the textured yarn shows the same impact as that of the staple fiber yarn. Low pre-twist offers less intensive migration, resulting in higher values of bulk, instability and extension but low pre-twist textured yarn gave less tenacity as compared to the textured yarn with higher pre-twist. Presence of crimps in the structure of textured yarn has executed higher boiling water shrinkage compared to the parent yarn.

Thus, the present study has shown a potential to texture selected non-thermoplastic viscose rayon yarn with desirable quality characteristics. Selection of variable process parameters, viz, pre-twist and false-twist have been undertaken as per end use.

Footnotes

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Acknowledgments

Samples of Viscose rayon yarns were gratefully received from the “Indian Rayon Ltd. Veraval” for our research on a donation basis. Experts from the industry and our institute professors have extended their help for subjective analysis.

References

Goswami

Martindale

Scardino

. Textile Yarns—Technology, Structure and Applications: Structurally Related Performance of Yarns, New York: Wiley-Interscience, 1976, pp. 84–85.

Usenko

. Processing of man-made fibers. Analysis of the twist–heat–set–untwist texturing process, Moscow: Mir Publishers, 1975, pp. 276–278.

Hearle

JWS

Hollick

Wilson

. Yarn Texturising Technology: Air-jet Texturing and Yarns, Cambridge: Woodhead Publishing Limited (CRC Press), 2001, pp. 211–243.

Ivanova

Lotarev

Shimko

. Textured viscose rayon filament yarn—Chemistry and technology of natural-polymer fibres. Fibre Chem+ 1971; 3(6): 656–658.

Ivanova

Mogilevskii

Shimko

. Formation of the bulked structure of textured viscose rayon. Fibre Chem+ 1974; 6(6): 650–652.

SwicoFil. Viscose rayon—The oldest manmade fibre—versatile fiber yarn, http://www.swicofil.com/viscose.html.

Finger

Baksheev

Mogilevskii

. Methods of improving the quality of viscose rayon filament yarn—Chemistry and materials science. Fibre Chem+ 1974; 5(6): 607–611.

Rao

MVS

Talele

. A Guide to Crimping/Texturising Technology, MANTRA Publications, Surat city of Gujarat, India, 1979, pp. 57–58.

Wilson

Kollu

. The production of textured yarns by the false-twist technique. Text Prog 1991; 21(3): 1–42.

10.

Demier

Acar

Wray

. Air-jet textured yarns: The effect of process and supply yarn parameters on the properties of textured yarns. Textile Res J 1988; 58: 318–328.

11.

Wray

. The properties of air-texturising continuous filament yarns. J Text Inst 1969; 60: 102–126.

12.

Hathorne

. Woven Stretch and Textured Fabrics: Patents, New York: Interscience Publishers, 1966, pp. 265–355.

13.

Bock

. Texturising filament yarns in an air flow-tangling mechanism. Int Text Bul (Spinning) 1981; 4: 359–359.

14.

DuPont. Characteristics of taslan textured yarns. Technical Information Bulletin X154, October 1961.

15.

Shaikh

Bhattacharya

. Mechanical crimp texturising: A novel concept. Textile Res J 2010; 80(6): 483–486.

16.

Shaikh

Bhattacharya

. Deriving an empirical formula to determine the optimum level of false-twist in mechanically-crimped textured polyester yarn. Textile Res J 2011; 81(19): 1995–2005.

17.

Bhattacharya

Shaikh

Pratap

. An investigation of thermal characteristic of mechanical crimp textured polyester yarn by differential scanning calorimeter (DSC). J Am Inst Phys 2010; 1249: 67–74.

18.

Shaikh TN. Development of an innovative method of texturizing. Doctoral Thesis, MSU Baroda, India, 2010, http://www.msubaroda.ac.in.

19.

Sen

Wray

. Apparatus for manufacturing yarns of the air jet bulked type without the use of air. J Textile Inst 1970; 61: 77–87.

20.

Hearle

JWS

Goswami

. Migration of fibers in yarns. Part VII: Further experiments on continuous-filament yarns. Textile Res J 1968; 38: 790–802.

21.

Weiss E and Wattwil KR. Patent 2,904,952, USA, 1959.

22.

Riding

. Filament migration in single yarns. J Textile Inst 1964; 55(1): T9–T17.

23.

Booth

. Principles of Textile Testing, Woburn, MA: Butterworth Heinemann, 1996, pp. 101, 234–235.

24.

R&D Centre Calico Mills. Standard for flat and textured polyester filament yarns. Synthetic Fibers, 1984, pp.24--27.

25.

ASTM Standards D 2256-02. Standard test method for tensile properties of yarns by single-strand method.

26.

Burnip

Hearle

JWS

Wray

. The technology of the production of false twist textured yarns. J Textile Inst 1961; 52: 343–369.

27.

Tretoar

LRG

. A migration-filament theory of yarn properties. J Textile Inst 1965; 56: T359–T380.

28.

Gupta

Hamby

. Fiber migration in staple yarns. Part I: Mean fiber position as a controlling factor and the influence of spindle speed and spinning tension. Textile Res J 1969; 39: 53–69.

29.

Hearle

JWS

Grosberg

Backer

. Structural Mechanics of Fibers, Yarns and Fabrics, New York: Wiley-Interscience, 1969.

30.

Hearle

JWS

Gupta

Merchant

. Migration of fibers in yarns: Part I: Characterization and idealization of migration behavior. Textile Research J 1965; 35: 329–334.

31.

Hearle

JWS

Bose

. Migration of fibers in yarns. Part II: A geometrical explanation of migration. Textile Res J 1965; 33: 659–699.

32.

Hearle

JWS

Gupta

. Migration of fibers in yarns. Part IV: A study of migration in a continuous-filament yarn. Textile Res J 1965; 35: 885–889.

33.

Hearle

JWS

Merchant

. Interchange of position among the components of a seven-ply structure: Mechanism of migration. J Textile Inst 1962; 53: T537–T552.

34.

Hearle

JWS

Goswami

. Migration of fibers in yarns. Part VI: The correlogram method of analysis. Textile Res J 1968; 38: 780–790.

35.

Hearle

JWS

Gupta

Goswami

. Migration of fibers in yarns. Part V: The combination of mechanisms of migration. Textile Res J 1965; 35: 972–978.

36.

Yildirim

Altun

Ulcay

. Relationship between yarn properties and process parameters in false-twist textured yarn. J Eng Fiber Fabr 2009; 4: 26–32.

37.

Fedorova

Novikov

. Determining the shrinkage of man-made fibres. Fibre Chem+ 1972; 4(6): 670–671.

38.

Gubaidullina

. Influence of twist on the physicomechanical properties of viscose rayon filament yarn. Physiomechanical properties and proccessing of man-made fibres. Fibre Chem+ 1978; 10(6): 61–62.