Twist-related parametric optimization of Joule heating-triggered highly stretchable thermochromic wrapped yarns using technique for order preference by similarity to ideal solution

A scalable approach for manufacturing highly stretchable thermochromic wrapped yarns has been reported previously. Herein, the effects of twist-related technological parameters, namely, wrapping density and outer-inner twist ratio are investigated and have been optimized by technique for order preference by similarity to ideal solution (TOPSIS). The results indicate that the preparatory twist-related parameters have a remarkable effect on the spiral geometrical configuration of yarn constituents, and thus in turn influencing the final tensile and elastic properties of wrapped yarns. The wrapping density of 800 T·m−1 and outer-inner twist ratio of 1.25 were considered as the optimal alternative using TOPSIS. Moreover, a negative relation between voltage and color-changing time of yarn spun with optimal parameters was established. It was also found that the color of yarn above elevated triggered voltages always switched from purple to pink but followed different color-changing paths. More importantly, thermochromic response of yarn is insensitive to the applied strain.