Self-twist Yarn Research Articles

Analysis of the Twist Influencing Factors of Self-twist Yarns

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Analysis of the Twist Structure in Self-twist Yarn

This paper mainly discussed the twist structure and property difference between in-phase self-twist yarn and phased self-twist yarn. There are three kinds of zones along the yarn: the twist-twist zone, twist-notwist zone and notwist-notwist zone in one cycle length of self-twist yarn. The existence of the phase difference makes the length of the notwist-notwist zone decrease. When the size of the phase difference (value c)is closer to or equal to the length of the zero zone(value b), the minimum length of the notwist-notwist zone will be obtained so that the best properties of self-0twist yarn can be achieved. The result for in-phase and phased self-twist yarn shows that the above conclusion is correct.

Characterization of the Twist Distribution Function and Twist Unevenness of Self-twist Yarns

In in-phase self-twist yarn there exists an obviously weak twist area between the twisted and no twisted zones. Therefore, during the self-twist spinning process, different distances from the two strands to the convergence point is adopted to produce a certain phase difference to improve the yarn strength. There are two methods used for calculating the twist distribution function of self-twist yarn: 1. using the difference in distance c, and 2. using the twist distribution function of strands A and B, respectively. Then the average twist over a half cycle length is calculated by the twist distribution functions from the two methods mentioned above. Comparing the calculation value from the two methods with actual test twists for the half cycle length, the result shows that the calculation value from method 2 is closer to the values measured, namely the twist distribution function derived from that of strands A and B, respectively. The twist unevenness of self-twist yarn is calculated by the twist distribution function from method 2. The twist unevenness of yarn 1 is the highest. That of yarns 2 and 3 decreases in turn. From the test data of 49×2 tex and 113×2 tex selftwist yarns, in-phase self-twist yarn 1, with maximum twist unevenness, has the minimum tenacity and maximum unevenness of tenacity, and in the same way phased self-twist yarn 3, with the minimum twist unevenness, has the maximum tenacity and minimum unevenness of tenacity.

A Mathematical Model for Self-Twist Yarn Spinning Process

A mathematical model is established for self-twist spinning process by applying laws of fluid mechanics (i.e. mass conservation and momentum conservation). The motion curve of the convergent point was determined and the convergence point was decided by densities and velocities of two fed-in strands and the resultant self-twist yarn, independent of their mechanical properties. The experimental verification proves that the motion trajectory of the convergence point reaches a better agreement with the theoretical trajectory. The results provide general way to study the self-twist yarn spinning process and optimize the process parameters.

Influence of Spinning Speed at Self-Twist Spinning System on Yarn Quality

The effect of spinning speed on yarn quality at self-twist spinning system was investigated. The yarns were assessed for different characteristics using objective tests. The results show that yarn hairiness of self-twist yarn increases with the increase of spinning speed and yarn tenacity and extension decrease with increment of spinning speed. The results also show that yarn irregularity, yarn imperfections and yarn twist level have no obvious changes with the increasing in spinning speed. Furthermore, the longitudinal and cross-sectional shape of self-twist yarn were observed and the pictures show that S-twist and Z-twist zone have almost the same structure as the two-plied yarn at ring spinning system and no twist zone has an approximately 45mm length which can influence the strength of the self-twist yarn.

The Use of Air-jet Technology to Produce Self-twist Yarn: Part II: The Application of Tandem Jet Twisters

Part I of (his series described the principle of using air-jet technology in a tandem arrangement to produce self-twist yarn. This paper deals with the application of tandem jets to replace the self-twisting roller with computer-controlled switching.

The Use of Air-jet Technology to Produce Self-twist Yarn: Part I: Preliminary Study

In the study reported in this paper, the possibility of using air-jet technology to produce a self-twist yarn was investigated. The method adopted used four jets in tandem, i.e. two Z and two S twisters, in which a high-pressure current of air was tangentially supplied to the inner surface of the yarn passage to create a vortex by which a strand of fibre was twisted.

Air Interlaced Self-Twist Yarns

An earlier investigation revealed that commingling self-twist yarn with a thin multifilament improved yarn appearance and strength. This paper describes a continued effort in that direction. Self-twist yarns are spun and air interlaced in a continuous operation on the Repco self-twist yarn spinning machine without the introduction of filaments. The abrasion resistance of the self-twist yarn is remarkably enhanced after air interlacing, especially in the zero-twist parts. When compared with counterparts made from self-twist and STT yarns, the knitted fabrics from the air interlaced self-twist yarn show improvements in handle and most mechanical properties, along with reduced knit loop distortion, which is inherent in ordinary self-twist yarn due to its structural variation.

Commingling Self-Twist Yarn with Filaments1

The air intermingling technique is used to impart filament cohesion in flat and textured multifilament yarns; more recently this technique has been used to combine filaments with spun yarns or elastomers to form composite yarns. In this investigation, a self-twist yarn was commingled with a thin, flat, multifilament yarn using an inter mingling air nozzle. The tensile properties of the commingled yarn were significantly improved in comparison with the self-twist yarn from which the commingled yarn was made. Self-twist yarn is notorious for its structural periodicity, which leads to fabric patterning. This has been reduced to almost invisibility in the commingled yarns. Experiments have also revealed that commingling increases yarn hairiness, which may impose adverse effects on yarn weaveability. Yarn structural examination shows that trapping the ST yarn between the filaments and wrapping the ST and filaments together with a small portion of self-twist yarn surface fibers are the two predominant kinds of bindings formed during commingling. The influences of air pressure in the commingling nozzle, yarn linear speed, and overfeed ratio are also reported.

Spirality Effects in Single-jersey Fabrics Knitted from Self-twist Yarns

Spirality Effects in Single-jersey Fabrics Knitted from Self-twist Yarns

18—OSCILLATING ROLLERS FOR SELF-TWIST SPINNING

A method is described for making self-twist yarns by using rollers that simultaneously rotate and oscillate. The technique provides a substantial improvement over previously known methods. The twisting action of sinusoidally oscillating rollers is examined theoretically and comparison made with twist levels observed experimentally. The resultant understanding enables machine parameters to be selected to give desired twist-cycle-length characteristics in in-phase self-twist yarns.

21—STT YARNS: TECHNOLOGICAL ASPECTS OF TWISTED SELF-TWIST YARNS

The STT system is one in which unidirectional twist is added to self-twist yarns to produce two-ply weaving yarns. The added twist required for the elimination of fabric patterning due to cyclic twist variation in the yarn has been determined and has been expressed in terms of the amount of self-twist in the yarn. Fabrics woven from STT yarns have been evaluated, and the dependence of fabric properties on initial self-twist and on added-twist levels has been investigated. This has resulted in recommendations for the spinning and twisting of STT yarns for use in making high-quality worsted fabrics.

20—TWIST DISTRIBUTION IN SELF-TWIST YARN

An examination has been made of the factors that affect the distribution of strand twist, and consequently of ply twist, for self-twist yarns. The yarns considered are in-phase self-twist yams produced on an oscillating-roller self-twist-spinning machine.

8—A MODEL FOR SELF-TWIST YARN

A simple model is used to derive an explanation for the stability of a self-twist yarn under an applied stress. This stability is a consequence of some degree of fibre entanglement and interlocking in critical regions of the yarn. In general, two smooth strands would not form a self-twist yarn.

8—A MODEL FOR SELF-TWIST YARN

A simple model is used to derive an explanation for the stability of a self-twist yarn under an applied stress. This stability is a consequence of some degree of fibre entanglement and interlocking in critical regions of the yarn. In general, two smooth strands would not form a self-twist yarn.

32—SELF-TWIST YARN

A new type of yarn structure, which has been named self-twist yarn, is described. It is a two-ply structure in which both the strand and plying twists alternate S and Z along the yarn. The strength properties of the yarn and their dependence on the various yam parameters are given for 60/64s wool fibres, and it is shown that the strength can approach that of conventional yarns.