Evaluation of Package Density Method for Measuring Bulk of Air-Jet Textured Yarns

Summary

Bulk is the most important characteristic of air-jet textured yarns. It plays a decisive role in determining the thermal and mechanical behaviour of fabrics made from these yarns and fabric comfort. Measurement of textured yarn bulk is therefore important in view of quality control. However, it is difficult to estimate bulk from the apparent diameter of air-jet textured yarns as the outer boundary of these yarns is affected by the projected loops. The bulkiness of a textured yarn is, therefore, normally measured by an indirect method. Out of the various methods proposed for measuring bulk, measurement of bulk through package density is most widely used. However, a number of variations in package density method are used for the bulk measurement. Both the textured and parent yarn packages are built to either same volume or wound for equal time on a winder. The size of the packages and winding tension affects the measured values of physical bulk.

While evaluating bulk through the package density method, as the package density varies with the change in package size and winding tension, there is a need for understanding the role of various factors in package building which affect the measured values of bulk and how the measured values of bulk correlate with the bulk realized in the fabric form. Therefore, we have studied the following:

(a). The influence of various parameters affecting the measured value of the textured yarn bulk.

(b). The measured values of bulk have been investigated in relation with fabric specific volume.

(c). The suitability of spindle and drum winder is also assessed.

Results presented in the paper show that parent and textured yarn packages of larger diameter should be wound in the case of equal diameter winding. In case the winder is not equipped with diameter indicator for control of package diameter, longer winding time should be used to build the parent and textured yarn packages for the measurement of physical bulk. In both

This paper was first published on the earlier Egytex website. The text above is the summary that was published there.