Effects of Alkali Treatment and Strain Hardening on the Mechanical, Dye Uptake, and Structural Properties of Regenerated Cellulosic Yarns

Abstract

Mercerization is an important process applied to cellulosic fibers for improving the properties like dimensional stability, luster, and dye uptake. Strain hardening is a technology for strengthening materials by realigning of atoms in crystal lattice and is generally used in metallurgy and is being tried on yarns. In the present study, four types of regenerated cellulose fiber namely lyocell, modal bamboo, and viscose were subjected to swelling by alkali (4% NaOH) treatment and Strain hardening by stretching device with the objective of studying mechanical properties, structural properties, and dye uptake properties. It is observed that tenacity was lowered below that of corresponding controls due to alkali treatment in case of all the four yarns. The strain hardening immediately after the alkali treatment enhanced strength of Bamboo and Modal upto 125% and 105% of the corresponding control yarns, whereas it was only 98% and 85% strength of corresponding untreated yarns in the case of Lyocell and Viscose. The minimum twist of cohesion values of alkali treated – strain hardened yarns were lesser than that of control and this is indicative of increase in inter fiber cohesion. Interestingly there was a tremendous improvement in dye uptake property of all four regenerated cellulosic yarns. This paper reports the impact of alkali treatment followed by stretching on essential properties of regenerated cellulosic yarns.

Keywords

• causiticasation
• strain hardening
• total crystallinity
• lateral order index
• tenacity