Twist contraction of jute multi-ply yarn – a theoretical approach

Abstract

Twist contraction is a critical phenomenon in ply yarn manufacturing. This study presents a theoretical model to predict the contraction factor of jute multi-ply yarns, accounting for the helical configuration of single yarns and the twist loss incurred during plying. The model integrates geometric parameters and twist mechanics to derive an expression for the contraction factor, incorporating both the helical path length and the incremental length change of single yarns due to untwisting. Theoretical predictions were validated through experiments using 2, 3, and 4-ply jute yarns of various counts and twist levels. Comparison between calculated and measured contraction factors demonstrated strong agreement, confirming the model's applicability.