Novel composite siro-spinning with forced migrations of filaments

Abstract

In this study, a novel composite siro-spinning method with cyclically migrating filaments was developed as a simple and safe way to enhance filament-staple-fiber coherence. The novel composite siro-spinning method was theoretically demonstrated to produce a yarn with migrated filaments clasping both internal and external fibers. It was predicted that migrated filaments of the novel composite sirospun yarn were not straight enough to resist yarn tensile drawing as the filament parallelism with the yarn axis decreased. However, migrated filaments could clasp the staple fibers firmly to enhance filament-staple-fiber coherence, contributing an excellent frictional resistance of the novel composite yarn. Experiments were then conducted to validate the demonstration. Experimental results proved that the novel composite sirospun yarn had cyclic filament immersion and exposure appearance, resulting in medium hairiness and yarn imperfection after comparison with corefil sirospun and siro corefil yarns. The novel composite sirospun yarn with severe filament migrations had poor filament straightness, but filament deformations that were effective in clamping staple fibers. Therefore, the novel composite sirospun yarn had less strength, but greater frictional resistance than corefil sirospun and siro corefil yarns.

Keywords

forced migrations siro-spinning yarn structure friction

Filaments are characterized by continuity, high strength, and regularity; these properties make it easy to twist the filaments together to form a continuous, smooth, and strong yarn.¹ Natural staple fibers are usually short and irregular, even sometimes weak; thus, they are easily shed and protrude from the yarn body to form hairiness, deteriorating the appearance and strength of the spun yarn. To overcome these disadvantages, filaments are employed to assist staple fibers in producing high-quality ring spun yarns, using ring composite spinning techniques, such as corefil spinning,^2–4 sirofil spinning,^5,6 and embeddable and locatable spinning.⁷

Corefil spinning produces filament-core and staple-sheath structured yarn by inputting the filaments in the center of one staple strand during spinning.^2,3 Therefore, corefil spun yarn has both the staple yarn hairy appearance and the filaments’ high strength.⁴ To reduce corefil yarn compactness and hairiness, filaments can also be fed into the middle of a pair of spaced staple strands to produce a corefil sirospun yarn.⁵ If one of the twin strands is replaced by a multifilament in a siro-spinning system, sirofil yarn will be produced, with uniform helix configurations of exposed surface filaments. Unfortunately, filaments are not fully clasped with staple fibers for sirofil and corefil yarns,⁶ causing easy structural damage and slippage between filaments and staple strands during the tensile drawing of yarns. To enhance the force of filaments clasping staple fibers, twin pre-twisted sirofil composite strands were ply-twisted together during embeddable and locatable spinning.⁷ Using this method, staple strands are effectively clasped by two filaments to produce a high-quality composite yarn.⁸ However, this method is still not widely used to produce cotton composite yarns, owing to its complex management of four precisely located components.⁹ To avoid complex management, cluster spinning has been developed; this involves electrostatically charging one multifilament cluster to produce outspreading monofilaments, which clasp staple fibers firmly in a spinning triangle zone.¹⁰ However, cluster spinning is also not widely applied for yarn production, because the electrostatic charge risks setting the spinning mill on fire.¹¹

With the aim of solving filament-staple-fiber slippage problems simply and safely, this study introduces a novel methodology that involves forcing cyclically migrating filaments, to enhance the filament-staple-fiber coherence of composite sirospun yarns.¹² This study is different from a previous study, which focuses on cyclic structural changed yarn using one multifilament and a single staple strand.¹³ In particular, the influence of filament migration between siro strands on yarn structure and properties is theoretically analyzed and predicted for the novel composite siro-spinning. A verified experiment is then conducted to produce novel composite sirospun, corefil sirospun, and siro corespun yarns on a ring frame. Thereafter, the structure and properties of all the composite yarns are comparatively investigated in detail.

Theory of novel composite sirospun yarn production via migrating filaments between siro strands

Geometrical principle of forced migrations inducing yarn structures with improved filament clasping of staple strands

As explained in the introduction, different composite yarn formation zone geometries result in structural variations in the composite yarn formed. If one staple strand is not overlapped with one fixed filament (i.e., sirofil spinning), the composite yarn structure exhibits remarkable and uniform helix configurations of the filaments and staple strand.¹⁴ The helix varies with the change in spacing between the staple strand and filaments. Unfortunately, the varied helical filaments are still exposed on the sirofil yarn surface,^15,16 failing to merge in the yarn interior to clasp internal staple fibers. By contrast, corefil yarn contains relatively straight inbuilt filaments^17,18 to enhance yarn strength.^19,20 Therefore, corefil yarn still has a hairy surface, as the inbuilt filaments do not contribute to the clasping of external surface staple fibers.^21,22 As a result, corefil yarns are easily fatigued after repeated damage, such as tensile loading,²³ or friction. If one filament can clasp both internal and external fibers, the yarn structure will be stable enough to resist repeated damage.

To improve the capacity to clasp staple fibers, a pair of staple strands and one forced oscillating multifilament are employed to produce a composite sirospun yarn with filaments’ migrations, as illustrated in Figure 1. The multifilament (denoted F in Figure 1) is overlapped with the left staple strand (denoted S₁), with the result that F is buried in the yarn body (Figure 1(a)). During the migration of F from S₁ to the right staple strand (denoted S₂), F first wraps onto S₁ (Figure 1(b)), then overlaps the convergence of S₁ and S₂ (Figure 1(c)), thereafter wraps onto S₂ (Figure 1(d)), and finally is buried in S₂ (Figure 1(e)). Subsequently, F migrates from S₂ to S₁, first wrapping onto S₂ (Figure 1(f)), then overlapping the convergence of S₁ and S₂ (Figure 1(h)), thereafter wrapping onto S₁ (Figure 1(i)), and is finally buried in S₁ (Figure 1(a)). It can be seen that the forced cyclic oscillation of F induces ample migrations to produce filament-locked structures within one complete cycle in the composite siro-spinning formation zone.

Figure 1.

Yarn formation zone shapes during the filament forced oscillation cycle: (a) F overlapping S₁; (b) F wrapping onto S₁; (d) F overlapping the converged S₁ and S₂; (e) F wrapping onto S₂; (f) F overlapping S₂; (h) F overlapping the converged S₁ and S₂; (i) F wrapping onto S₁.

Structural model of novel composite yarn with improved filaments clasping staple strands

According to the aforementioned principle analysis, F overlapping S₁, or S₂, results in a corefil sub-strand, which twists with the staple sub-strand to form a composite yarn (termed corefil sirospun yarn) structure, in which the filament is located in the core-part of one staple sub-strand (Figure 2(a)). Obviously, it is desirable that there is no exposed filament helix on the corefil sirospun yarn surface. The ascending cyclic lifting motion of the ring rail^24,25 incurs tension variations of the spinning strand. Therefore, the twisting triangle of the siro-spinning is continuously changing throughout one bobbin yarn production. The constant changes of the twisting triangle scarcely keep F overlapping the middle point of S₁ and S₂, which converge all the time, causing F to be easily exposed on the siro corefil yarn surface with the same helix of each sub-staple strand (Figure 2(b)). The created filament migrations (Figure 1) within the novel composite sirospun yarn structure can grasp the two sub-staple stands alternately as much as possible to improve the filament-staple fiber coherence (Figure 2(c)). In particular, the novel composite yarn surface is characterized by much greater filament exposure than the siro corefil yarn; most of the exposed F helix on the novel composite yarn surface is more perpendicular to the yarn axis than that on the siro corefil yarn.

Figure 2.

Different composite siro-spun yarn structures: (a) desired corefil sirospun yarn with filaments buried in yarn structure; (b) practical siro corefil yarn with exposed helical filaments; and (c) novel composite sirospun yarn with forced filament migrations.

Mechanical property prediction of different structures of composite sirospun yarn

Although composite yarn mechanical properties can be improved by using strong filaments, the improvements are determined by composite yarn structures. For the improvement of yarn tensile strength, the filament is desired to be parallel with the yarn stem, straight enough to resist tensile damage. Otherwise, the filament strength contribution may be reduced until the filaments are perpendicular to the yarn stem. Accordingly, the following equation can be used to compare filament tensile strength contribution

η_{strength} = \frac{S_{F} \times sin | 90 - θ |}{S_{F}} = sin | 90 - θ |

(1)

where η_strength represents the filament tensile strength contribution ratio, S_F represents strength of the filament, and θ represents the angle between the filament helix and yarn axis, which ranges from 0° to 90°.

Obviously, the value of θ for exposed filaments of the novel composite sirospun yarn is much greater than that of the desired corefil sirospun yarn and the practical siro corefil yarn (as shown in Figure 2). Thus, it is predicted that the novel composite sirospun yarn will have weaker strength than the corresponding corefil sirospun yarn and practical siro corefil yarn.

To produce improvements in yarn friction, the filament is desired to clamp the staple fibers as tightly as possible, preventing fibers from being pulled out or worn off from the composite spun yarn body. In-buried filaments do not contribute to protecting exposed staple yarn surface from fiber loss by friction. However, exposed filaments wrapping the yarn stem can resist friction to improve spun yarn abrasion resistance. Therefore, the siro corefil and the novel composite sirospun yarns have better abrasion resistance than the corefil sirospun yarn, owing to their surface-exposed wrapping filaments. In particular, the novel composite sirospun yarn contains migrated filaments that clasp both internal and external fibers (Figure 2), enhancing yarn filament-staple-fiber coherence during repeated friction. The complex migrated filaments embracing staple fibers are not easily damaged, preventing composite yarn breakage. Thus, the novel composite sirospun yarn is considered to have the maximum abrasion resistance.

To validate the theoretical analysis, experiments were conducted to examine the yarn structures and related yarn properties.

Experimental detail

Instead of the eccentric device used in a previous study,¹³ an electric device (Figure 3) was installed on a experimental HFX-A6 type ring frame to force filaments (guided by traversing godet wheels) to perform migrations during their inputting into the front roller nip (Figure 4), causing periodic changes in the filaments’ position in the composite sirospun triangle. The migration frequency (or speed) of the godet wheels was set at 80 times/min to produce a novel composite sirospun yarn.

Figure 3.

Electric device to guide filament migration.

Figure 4.

Filament migration device for novel composite siro-spinning. A single godet performing reciprocating transverse motion from the right (a), to the middle (b), and left (c), then from the left (c), to the middle (b), and right (a).

With the godet static, filaments are fed into the front roller nip by overlapping the right sub-strand and locating them in the middle of the twin strands to produce corefil sirospun and siro corespun yarns, respectively. Combined filaments (20D/12F black polyester + 30D gray polypropylene) and two 4.8 g/10 m white cotton rovings were used to produce each composite yarn with the same spinning settings: drawing ratio, 36.36; spindle speed, 5600 r/min; front roller speed 101.9, r/min; ring type, PG1-4254; traveler type, UDR 5/0; twist density 700, twists/m. The novelty spinning with forced filament migrations was recorded using the camera of an Apple 5 S smart phone.

All the composite yarns were stored for at least 24 hours under a standard atmospheric condition (20 ± 2℃ and 65 ± 2% relative humidity). All composite yarns were examined for longitudinal and cross-sectional appearance under an OLYMPUS DSV510 fully automatic optical microscope; the magnifications are all 69 × . The yarns were also tested in terms of hairiness, unevenness (CV%), and tensile properties. The hairiness test was conducted using a YG171B-2 hairiness meter, with a test speed of 30 m/min, a test segment length of 10 m. Ten successive segments were tested for each yarn according to the Chinese textile industry standard FZ/T 01086-2000. According to the CN GB/T 3292-1997 capacitance testing standard, a USTER ME 100 evenness tester was used to test yarn unevenness and imperfections; the testing speed was 400 m/min, and the testing length for each samples was 400 m. A YG068C type automatic single yarn tensile tester was employed to test the tensile properties of the yarns; each sample was tested 20 times at a test speed of 500 mm/min and a gauge length of 500 mm. A FFZ622 type yarn frictional resistance tester with was employed to examine the frictional properties of different yarn samples according to the CN FZ/T 01058-1999 standard (abrasion resistance of yarns: reciprocating rubbing roller method). Sampled yarn, straightened using a 20 g balancing weight, was rubbed with 600 mesh sandpaper to produce fracture; each yarn was tested 60 times. The composite sirospun yarn friction variations were also recorded using an Apple 5 S smart phone camera.

Results and discussion

Online filament migration in novel composite siro-spinning triangle

The filament migration guide device forced the filaments to change their output positions dynamically from the front roller nip, causing the filaments to perform cyclic migrations in the yarn formation zone (as shown in Figure 5). It can be seen that the practical filament migration path in the novel composite sirospun yarn formation zone is consistent with the theoretical prediction (Figure 1).

Figure 5.

Forced migrations of combined filaments during composite siro-spinning: (a) filaments overlapping the left staple strand; (b) filaments wrapping onto the left staple strand; (c) filaments overlapping the converged two staple strands; (d) filaments wrapping onto the right staple strand; and (e) filaments overlapping the right staple strand.

Structural appearance of different composite yarns

The geometrical differences in the yarn formation zone would cause yarn structural changes. When the combined filaments overlapped the left sub-strand, most of the filaments were spun into the inner structure of the corefil sirospun yarn; only occasional parts of filaments were not well covered by the staple wrappings (Figure 6(a)). This might result from the larger thickness of the combined filaments. Considering the exposed filament spots, the included angle between the helix filament and the yarn stem axis is about 20°. On the siro corefil spun yarn surface, the filament helix is clearly and uniformly exposed (as shown in Figure 6(b)). In this case, the angle between the helical filaments and the yarn axis is about 35°. Uniquely, the novel composite sirospun yarn has a migrated filament with a high included angle between the helix filament and yarn stem axis; the maximum angle is about 47°, as shown in Figure 6(c). In addition, all the yarn sectional stem diameters remained roughly unchanged, which might be due to the sub-strand pre-twisting decreasing the yarn volume variations.

Figure 6.

Longitudinal appearance comparisons of different yarns: (a) corefil sirospun yarn; (b) siro corespun yarn; and (c) novel composite sirospun yarn.

Surface hairiness of different composite yarns

Table 1 shows that the siro corespun yarn had fewer surface hairs than the other two composite yarns; this is mainly due to the evenly distributed exposed filaments wrapping the staple strand. By contrast, nearly all the filaments buried in the corefil sirospun yarn body did not contribute to a reduction in yarn hairiness; therefore, the corefil sirospun yarn was more hairy than the siro corespun and the novel composite sirospun yarn with filament migration. The novel composite sirospun yarn with filament migration had a medium yarn hairiness, owing to its intermittent filament corespun and filament wrapped spun sections. This result shows good consistency with the previous theoretical analysis.

Table 1.

Hair number comparison of different composite yarns per 10 m

	Yarn hair length
	1 mm	2 mm	3 mm	4 mm	5 mm	7 mm	10 mm	12 mm
(a) Corefil sirospun yarn	1773.90 ± 59.35	421.90 ± 35.52	171.50 ± 17.73	66.30 ± 8.34	27.20 ± 4.18	5.10 ± 2.23	0.50 ± 0.53	0.00 ± 0.00
(b) Siro corespun yarn	1455.50 ± 7.86	294.30 ± 19.61	84.80 ± 9.26	24.40 ± 6.17	9.40 ± 4.30	2.10 ± 1.97	0.10 ± 0.32	0.20 ± 0.42
(c) Novel composite sirospun yarn	1581.00 ± 96.45	376.40 ± 39.58	135.00 ± 19.35	48.90 ± 11.57	20.20 ± 6.41	4.60 ± 2.55	0.60 ± 0.70	0.00 ± 0.00

Irregularity of different composite yarns

Table 2 shows that the corefil sirospun yarn had a higher irregularity than the other two composite sirospun yarns. This might be caused by an asymmetric spinning triangle and bad staple fiber trapping in the corefil sirospun yarn formation zone. The unstable and irregular spinning triangle could also encourage a dramatic uneven loss of staple fibers, increasing yarn imperfections, and producing thick and thin places. Additionally, the corefil sirospun yarn had the greatest hairiness of the three composite yarns; excessive hairiness would be entangled together on yarn surface to form neps.²⁶ Therefore, corefil sirospun yarn had more yarn imperfections (i.e., thick places, thin places, and neps) than the other two composite yarns.

Table 2.

Irregularity parameters of different composite yarns

	CVm, %	Thick places +50%, km	Neps +140%, km	Neps +200%, km
(a) Corefil sirospun yarn	12.24	170.00	100.00	80.00
(b) Siro corespun yarn	11.42	0.00	20.00	20.00
(c) Novel composite sirospun yarn	11.31	20.00	30.00	20.00

According to the theoretical prediction and the experimental results, the novel composite sirospun yarn showed a linear combination of corefil sirospun and siro corespun yarn sections (Figure 6). The practical novel composite sirospun yarn included a moderate amount of yarn imperfections, including thick places and neps, but this value was not the arithmetic mean of the values for the other two yarns. This was mainly because the corefil sirospun yarn imperfection deviated from the normal value in that there was a dramatically uneven fiber loss. Surprisingly, the novel composite sirospun yarn had the smallest unevenness (CVm) of the three composite yarns. This might be because the novel composite sirospun yarn included longer linear uniform filaments than the corefil sirospun and siro corespun yarns within an equal yarn section; yarn irregularity will be decreased after combination with linear uniform materials.²⁷

Tensile properties of different composite yarns

Usually the higher the yarn irregularity is, the weaker the yarn will be.²⁸ Table 3 shows that the corefil sirospun yarn was stronger than siro corespun yarn, which was stronger than the novel composite sirospun yarn. It is clear that the tensile strength results did not agree with the irregularity results. However, the results validated that the filament straightness within the composite yarn structure, and the negative trend of the maximum angles between helical filaments and the yarn axis, was the decisive factor affecting yarn tensile strength. The maximum angles were 20°, 35°, and 47° for corefil sirospun, siro corespun, and the novel composite sirospun yarns, respectively. Therefore, the novel composite sirospun yarn was weak to resist tensile drawing (i.e., 669.51 < 687.38 < 725.85), as its structural curve filaments were exposed to a large destructive shear force. By contrast, the corefil sirospun yarn with relatively straight filaments was difficult to break, owing to the minimum destructive shear force occurrence during tensile drawing.

Table 3.

Tensile property information of different composite yarns

	Breaking force, cN	Elongation ratio, %	Breaking work, cN.cm
(a) Corefil sirospun yarn	725.85 ± 69.90	8.55 ± 0.58	1299.19 ± 201.99
(b) Siro corespun yarn	687.38 ± 54.91	7.64 ± 0.49	1126.62 ± 168.34
(c) Novel composite sirospun yarn	669.51 ± 59.26	8.16 ± 0.57	1131.20 ± 161.04

Frictional properties of different composite yarns

Unlike the tensile strength, frictional properties were closely related with yarn structural stability and fastness. Showing good consistency with the aforementioned theoretical prediction, corefil sirospun yarn had a poor frictional resistance (i.e., 133.09 < 209.97 < 230.38), since the filament core contributed nothing to the staple-sheath fastness. When the filaments were exposed on the yarn surface by helical wrapping onto the siro corespun yarn body, the yarn friction resistance increased by 57.76%; this is mainly because the helical strong filament wrappings could resist frictional destruction. Within the novel composite spun yarn structure, migrated filaments were not only exposed on the yarn surface to resist fractions, but also nested with each sub-strand to fasten staple fibers. Thus, the novel composite yarn achieved the best friction resistance (Table 4).

Table 4.

Frictional property information of different composite yarns

	Friction times when end-breaking	Yarn friction increasing ratio compared with that of corefil sirospun yarns, %
(a) Corefil sirospun yarn	133.09 ± 26.16	0.00
(b) Siro corespun yarn	209.97 ± 34.53	57.76
(c) Novel composite sirospun yarn	230.38 ± 32.63	73.10

Almost all corefil sirospun yarn samples were broken after 180 repeated friction movements (Figure 7(a)). Most of the novel composite sirospun yarn sample still remained continuous after 200 repeated friction movements (Figure 7(c)), revealing excellent frictional resistance. Comparatively, there were much fewer unbroken samples of siro corespun yarns than of the novel composite sirospun yarn after 200 repeated friction movements. Therefore the siro corespun yarn had a worse friction property than the novel composite sirospun yarn, which was in good agreement with theoretical prediction.

Figure 7.

Wearing images for different yarns after various repeated frictions: (a) corefil sirospun yarn; (b) siro corespun yarn; and (c) novel composite sirospun yarn.

Conclusions

A novel composite siro-spinning method that involved forcing filaments to migrate cyclically was developed to solve problems of weak coherence and easy slippage between filaments and staple fibers. Theoretical analysis indicated that filament migrations within the novel composite sirospun yarn can be produced by cyclically forced oscillation of filaments, largely enhancing the filament clasping of internal and external staple fibers in the yarn geometry. Unfortunately, the migrated filaments of the novel composite sirospun yarn were so curved that it could not perform an excellent release of their full strength to resist yarn tensile drawing. By contrast, the migrated filaments with high curve and deformation could fasten the staple strands firmly, resulting in an excellent frictional resistance for the novel composite sirospun yarn.

A filament migration motivation device was applied to conduct a verified experiment on a ring frame. Online observation of the novel composite siro-spinning showed that the filaments were dynamically forced to change their output positions, performing cyclic migrations in the yarn formation zone. Yarn appearance results validated that the novel composite sirospun yarn had a periodical filament immersion and exposure without obvious yarn diameter variations. This meant that the novel composite sirospun yarn had moderate hairiness and yarn imperfections, as compared with the corefil sirospun yarn with filament immersion and the siro corespun yarn with filament exposure. The novel composite sirospun yarn had weaker strength (669.51 cN), but much greater durability (230.38 friction times) to rubbing than corefil sirospun (725.85 cN; 133.09 friction times) and siro corefil (687.38 cN; 209.97 friction times) yarns. The results were agreed well with the theoretical prediction.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the the Natural Science Foundation of Hubei Province (grant number 2017CFB577) and the State Key Laboratory of Bio-Fibers and Eco-Textiles (grant number KF 2017kfkt09).

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