Twist distribution in staple fibre yarns

Abstract

Staple fibre yarns vary quite markedly in linear density (tex) along their length and the degree to which twist redistributes from thick to thin places will affect the strength, torque and extension behaviour of the yarn. Theory suggests that twist along worsted yarns should vary as 1/(tex)² if fibres were locked in the structure, whereas the mean torque of worsted yarns reported in the literature implies that twist should be proportional to 1/tex. This article examines twist distribution in ring-spun marl yarns, down to 5 mm resolution, as a function of linear density measured using a high-resolution capacitive sensor. It is found for moderate twist-level worsted yarns that twist is approximately proportional to 1/(tex)^1.6. The results and theory provide a guide as to the effect the observed large variations in linear density will have on yarn properties such as tenacity and torque.

Keywords:

• twist distribution
• tenacity
• torque
• worsted yarn
• linear density

Acknowledgements

Support from CSIRO Textile and Fibre Technology in the supply of rovings and capacitive sensors is gratefully acknowledged. Financial support for this project was provided by the Australian Research Council (ARC).