INTERCHANGE OF POSITION AMONG THE COMPONENTS OF A SEVEN-PLY STRUCTURE: MECHANISM OF MIGRATION.

The migration pattern in a seven-ply structure is predicted theoretically on the assumption that the centre filament moves to an outer layer only when it is slack. The frequency of migration is dependent on the twist, the twisting tension, the free length in the twisting zone, the tension resulting from an extension of the yarn, and the degree of buckling needed to initiate migration. If the tension is high enough, migration will be prevented. The theoretical predictions were confirmed by a study of the twisting of seven 100-denier twisted viscose rayon yarns on an apparatus specially constructed to twist model yarn samples. The order of migration indicated that, of the six yarns in the outer layer, the yarn which had last migrated had a low, but not zero, probability of moving back to the centre, but that the other five had equal probability. Subsidiary experiments were performed on Courlene monofilaments and zero-twist rayon yarns. [ABSTRACT FROM AUTHOR]