Effect of dyeing process on tensile strength properties of polyester/cotton blended yarns

The change in the tensile strength properties of 45 Ne polyester/cotton(40/60) blended yarn after dyeing process has been investigated. The tensile strength properties of the grey yarn have also been tested for comparison. In the blended yarn, the polyester component is first dyed with disperse dye followed by the dyeing of cotton component with reactive dye. After dyeing both of the polyester and cotton parts, wax based softener is used for finishing. It is observed that there is a significant drop in tenacity of the yarn along with the gain in elongation-at-break after the dyeing in comparison of grey yarn. The tensile strength properties are investigated at three stages, viz immediately after dyeing of polyester component, after dyeing of cotton component and then after the application of softener. It is found that the drop in tenacity of the yarn after dyeing of cotton part is much higher than the drop found immediately after polyester dyeing. The value of elongation-at-break has increased very significantly after dyeing of polyester component. The elongation-at-break drops after dyeing of cotton component but remains always higher than the grey yarn. The softener application also plays a role in drop of tenacity and increase in elongation-at-break.