The relevance of false-twist addition on ring spun yarns by means of rotary threaded surfaces

A novel concept of producing false-twist yarns by cyclical stress fluctuation was developed. The forming principle was introduced to analyze the formation process of false twists on rotary threaded contact surfaces. Geometric analysis indicates that cyclical stress variations produce extra rotations (false twists) on fiber strands in the yarn formation area, causing twist redistribution and fiber arrangement remodeling with the appearance of local fiber reversion. Theoretical analysis reveals that more false twists are produced when the spun yarn is in contact with surfaces of high traverse speeds. Then, a motion simulation model using different traverse speeds of the threaded contact surface was established to compare the yarn internal stress variation, verifying the false-twist efficiency at different traverse speeds. Finally, a systematic comparison was conducted between the yarns spun at different traverse speeds. It was shown that the yarn properties improved with higher traverse speeds of the threaded contact surface, achieving less hairiness, high yarn strength, and low residual torque.

Mixed versus Networked Bio-Based PA56/Polyethylene Terephthalate Composite Yarns: A Study of Two Modification Methods

Two bio-based PA56/PET composite yarns were manufactured in this study, namely, the mixed and networked composite yarns, by using different modification methods. The results showed that the effect of mixing modification by adding the bio-based PA56 into PET was unsatisfactory. When the ratio of the added bio-based PA56 was smaller than 30%, the modification effect was insignificant; while the ratio was above 30%, the dispersion uniformity was very poor. There were also the problems of the fast rise of pressure in the component and pre-filter, short life cycle, a large number of broken ends, and low production efficiency. Then the bio-based PA56 and PET drawn false- twist textured yarns (DTY) were respectively prepared and manufactured into networked composite yarns. The manufacturing of the networked composite yarns went smoothly. The fabrics woven with the networked composite yarns achieved shade variation with one dye.

Experimental study on the formation of core-spun yarn manufactured on a modified vortex spinning system

Aiming at achieving online monitoring of the yarn formation process of vortex spinning, this paper presents a direct observation method that adopts a charge-coupled device camera fitted with an industrial endoscope that can reach into the nozzle chamber through a small hole drilled on the nozzle wall. Local pressure distortion in the vortex chamber due to the mounting of the observation apparatus was found experimentally. However, the yarn quality was not significantly affected, indicating that the proposed method has the potential to find industrial applications. Based on this method, the formation process of core-spun yarn containing a copper wire manufactured on a modified vortex spinning system is successfully observed. The results show that the core wire is covered by the main strand (core fibers), while the main strand is false-twisted during the yarn formation process. The level of false twist in the main strand fluctuates with time. The level of false twist in the main strand is higher in the upstream region, while it gradually decreases toward the downstream. Mostly, the trailing ends of some fibers are separated from the main strand and expand over the spindle tip to wrap around both the core fibers and core wire to form wrapper fibers in the yarn, while the leading ends of a smaller number of fibers are separated to form wrapper-wild fibers in the yarn. The proposed method can be extended to the study of fiber movement in confined spaces in other textile manufacturing processes.

Dependence of Structural Characteristics of Polyamide Textured Yarns on the Parameters of the False Twist Yarn Texturing Process

In the false twist texturing process, due to the action of mechanical forces and heat, a disorientation of structural elements happens at all levels of the supramolecular structure. These changes are related to changes in the texturing parameters and mechanical properties of yarn. In this paper, investigated is the effect of technical-technological texturing parameters in the false twist texturing process on the structure of PA6.6 yarns. POY multifilament PA6.6 with a fineness of 22f07x1 dtex was used as experimental material. The yarn was textured on a friction texturing machine - ICBT model FT 15 E3. The exiting yarn speed (Vi) changed as 600, 700, 800 and 900 m/min; the heater temperature (T) was 200, 210 and 220 °C, and the ratio of the disk surface speed to the linear yarn speed (D/Y) was 1.9 and 2.1. The values of strain were kept constant at 1.305 (tension in texturing zone) and 0,954 in the winding zone. Analysed were the density, degree of crystallinity, degree of orientation, single filament diameter, the content of -NH2 and -COOH end groups, and the total content of end groups. From the results obtained it can be seen that the effect of the heater temperature is more significant than that of Vi and D/Y on the structural characteristics analysed. Analysing the experimental results it was found that linear positive correlations were established between the texturing speed and end (-NH2) groups, the texturing speed and end (-COOH) groups and the texturing speed and the total content of end groups. The correlation factor between the process parameters and yarn structural characteristics analysed is determined.

Variation of false twist on spinning process stability and resultant yarn properties in a modified ring spinning frame

Twisting is an important process to form a continuous yarn from short fibers and to determine the structure and properties of the resultant yarn. This article reports on the effect of variation of false twist on process stability and resultant yarn quality in a modified ring spinning frame. Based on twist kinematics, three practical cases that cause twist variations in the spinning process are investigated, namely step function, rectangular function and periodic function changes in false twist. The simulation results are validated by experiments and a good agreement has been demonstrated. The resultant properties of yarn within 30% periodic change in false twist demonstrated insignificance compared with yarn without variation. With the developed model, essential system parameters are numerically examined and their quantitative relationships are studied. The practical implications are discussed.

The effect of false-twist texturing parameters on the structure and crimp properties of polyester yarn

In this paper, the effect of false-twist texturing parameters (texturing speed, heater temperature, draw ratio and disc-to-yarn speed ratio (D/Y ratio)) on the structure and crimp properties of polyester yarn has been studied using a high temperature heater and high texturing speeds. Textured yarn was analyzed and characterized in terms of the degree of crystallinity, degree of orientation and crimp properties (crimp contraction, crimp module and crimp stability). The most important parameters, significantly affecting yarn temperature and its uniformity and thus textured yarn structure and crimp properties, are texturing speed and heater temperature. Depending on these texturing parameters, the degree of crystallinity and orientation varied in the range of 24.48 to 36.66% and 0.371 to 0.595, respectively. The crimp characteristics increase with the increase in heater temperature, and decrease with the increase in texturing speed. The effect of draw ratio and D/Y ratio on the textured yarn structure and properties is less pronounced. Obtained results show that partially oriented polyester yarn used in this study can be textured at significantly higher texturing speed (up to 1100 m/min) than the standard texturing speed (up to 700 m/min) used for the yarn count examined.