Yarn Break

The spinnability and spinning properties of a polymer are of the highest importance in the manufacturing of staple fibers and filaments. There are many analogies to the production of films, where breaks or splits are concerned. The frequency of yarn breaks determines the economic viability of the production process, as well as the competitiveness and the reputation of the manufacturer. Today, in the age of automation, it would be theoretically possible to manage the processing of the polymer with a minimum of staff if no yam breaks disturbed the processing. 

The occurrence of yam breaks was reported early and is connected with thickness fluctuations in extruded ribbons or films, as described collectively by the phenomenon of draw resonance , which is characterized by oscillations of the fiber diameter, which ultimately lead to yarn break. The latter is defined as brittle fracture and is thus related to melt temperature, molecular weight, quenching conditions, and particularly to the role of viscoelasticity, as described in the following section. 

Figure 13.1 Yarn break caused by skin-core differences (brittle fracture and crazes) [9]. Photograph provided by W. Goltner...

In addition, the drawability of a spun yam can be measured in a similar way by increasing the draw ratio up to yarn break at an experimental drawing position. The optimal draw ratio can also be deduced from the stress-strain curve of the spun yam. 

In any case, the appearance of fluorescence is accompanied by significantly reduced spinnability. Figure 13.19 shows an impressive example of the fluorescence of three PET samples with different spinnability. The term excellent is here applied to the processability of polymer A, which is by far superior to that of the other two samples. Polymer A could be processed without almost any yarn breaks in POY spinning (167 dtexf 32,1 winding speed 3300m/min), polymer B showed an acceptable performance, whereas polymer C gave many yam breaks and therefore a bad performance. The break rate is proportional to the... 

Card Web Yarn-Break Yarn Yarn Yarn... 

Cotton Spindle speed (rpm) EDMSRa Yarn Break Factor Units Yarn Neps per 914.4 m Yarn CV (%)... 

The load-displacement curves for the orthogonal interlock fabric composites show a non-linear unloading sequence and an appreciable permanent deformation after unloading, with the crack tip not completely closed (Guenon et al., 1987). These observations are attributed to the crack closure process of the three-dimensional fabric composites where through-the-thickness yarns break near the outer surface of the specimen. 

Information in Table II describes the performance characteristics of typical seed cotton drying systems and Illustrates some of the effects of drying fibers to a level below the optimum. Generally, these data show that fibers ginned at moisture contents below 6 percent were shorter and produced lower yarn break factors than fibers ginned at moisture contents above 6%. Obviously, the amount of energy required for drying... 

Based on average of contemporary fibers as 100%. Yarn break at zero-gage length. 

The stress-induced crystallization influences the ability to sustain the stress of deformation occun ing in tire spin line. Optical micrographs of fluffs allow the assumption of different deformation or sttess behavior of core and skin layers of spun fibers, as shown in Eigure 13.1. The reason for this kind of yarn break can... 

Thermal-oxidative degradation is an additional reason for yarn breaks commonly observed during polymer processing as a consequence of leaks in die equipment. Frequent testing of tightness is dierefore an important part of production... 

BS 1932. Part 2. 1989. knot strength ratio is defined as the ratio of the knot breaking strength (as measured in BS 1932. Part 2) to the yarn breaking strength (as measured in accordance with ISO 2062). 

Drop wires n. A stop-motion device utiILzing metal wires suspended from warp or creeled yarns. When a yarn breaks, the wire drops, activation the switch that stops the machine. 

Stop motion n. Any device that automatically stops a textile machine s operation on the occurrence of a yarn break, a high defect count, etc. 

Relation of Cotton Fiber Properties to Yarn Breaking Elongation... 

Sequential multiphase looms provide sequential sheds in the warp direction, each for one weft insertion. This principle has been known for a long time. At ITMA1995, Sulzer-Riiti presented its sequential multiphase weaving loom M 8300 (Fig. 4.25). Despite the high production speed (up to 5000 m/min), it was no commercial success, the main reasons being the low flexibility regarding patterns and the difficulties when fixing a weft yarn break. 

It is important to note that certain parameters cannot or can only inaccurately be modeled. This comprises machine standstills and yarn breaks that depend on a large number of parameters that cannot or can only barely be measured. 

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