High speed spinning machines generate more friction thus giving additional heat to the yarn and as a result of such heat transfer the yarn moisture content is vaporized. Rising speeds in spinning result in decreased yarn quality for other processes and it is well known that dry yarns have worse properties. For quality reasons it is absolutely important to have even distribution of this recuperated moisture throughout the entire yarn package. Only the vacuum technology provides the conditions for the required moisture regain. This paper attempts to comprehensively review the yarn conditioning mechanism, process parameters of conditioning and applications of yarn conditioning.
Moisture in atmosphere has a great impact on the physical properties of textile fibres and yarns. A high degree of moisture improves the physical properties of yarn and it helps the yarn to attain the standard moisture regain value of the fibre. Yarns sold with lower moisture content than the standard value will result in monetary loss. Therefore the aim of yarn conditioning is to provide an economical device for supplying the necessary moisture in a short time, in order to achieve a lasting improvement in quality.
In these days there is a dramatic change in the production level of weaving and knitting machines, because of the sophisticated manufacturing techniques. Yarn quality required to run on these machines is extremely high. In order to satisfy these demands without altering the raw material, it is possible to make use of the physical properties inherent in the cotton fibres. Cotton fiber is hygroscopic material and has the ability to absorb water in the form of steam. It is quite evident that the hygroscopic property of cotton fibers depends on the relative humidity. The higher the humidity is, more the moisture absorption. The increase in the relative atmospheric humidity causes a rise in the moisture content of the cotton fiber.
The fibre strength and elasticity increase proportionately with the increase in humidity. If the water content of the cotton fibre is increased, the fibre is able to swell, resulting in increased fibre to fibre friction in the twisted yarn structure. This positive alteration in the properties of the fibre will again have a positive effect on the strength and elasticity of the yarn.
Problems in conventional yarn conditioning method
The standard conventional steaming treatment for yarn is chiefly used for twist setting to avoid snarling in further processing. It does not result in lasting improvement in yarn quality. The steaming process may fail to ensure even distribution of the moisture, especially on cross-wound bobbins (cheeses) with medium to high compactness (Fig. 1).
The absence of vacuum in conventional conditioning chambers prevents Conventional homogeneous penetration. The outer layers of the package are also too moist and the transition from moist to dry yarn gives rise to substantial variations in downstream processing of the package, both with regard to friction data and strength.