Effect of mercerization on the tensile properties of rotor spun yarn

Rotor spun 14s cotton yarns were twisted over a range of twist multipliers from 4.25 to 5.5. The yarns were mercerized with sodium hydroxide and stretched to their original length. Tenacity of mercerized yarns was significantly greater than the grey yarns at all twist levels. A substantial improvement of 52.8% in tenacity was observed at the lowest twist. Even slack mercerization improved yarn tenacity at lower twist levels (up to 4.7) close to that for tension mercerized yam. Maximum increase in yarn tenacity by slack mercerization was 46% at the lowest twist. Tension mercerization increases yarn tenacity primarily by improvement of fiber packing at lower twist levels, but at higher twist levels fiber orientation, fiber packing, and improvement in fiber tenacity all affect yarn tenacity.