Dye distribution in the dyeing of mixed denier polyester fabrics

Microfibre polyester is sometimes blended with higher denier fibres to achi eve good aesthetic effects at lower cost. Two polyester yarns of 1.4 and 0. 7 denier were dyed singly and together with a range of depths of CI Dispers e Blue 79, and the dye distribution over the course of the dyeings was exam ined. The uptake is initially greater on the microfibre, but as dyeing is c ontinued the distribution becomes more even, and eventually the same concen tration of dye is present on both fibres. Based on the common observation t hat a given concentration of dye produces a lighter shade on a microfibre, the redistribution of dye during the process causes a continuing shade chan ge even though the bath exhaustion is constant. A mixture of three dyes pro duced a stable hue on a fabric of 1.0 denier polyester after 20 min at a fi xed dyeing temperature, but when dyed on a fabric of 1.0 and 0.5 denier yar ns, a change in hue continued for more than 60 min.