Eco-friendly Indigo Dyeing of 3D-Printed Thermoplastic Polyurethane Material Using Glucose and Calcium Hydroxide

In this research, natural dyeing studies were conducted using indigo, and dyeability was compared using sodium hydroxide, calcium hydroxide, and calcium carbonate as bases. As a reducing agent, sodium hydrosulfite and glucose were compared. For a more environmentally friendly method, 3D-printed thermoplastic polyurethane (TPU) materials were dyed with natural indigo using glucose as the reducing agent and calcium hydroxide as the alkali. The dyeability of TPU materials was investigated under various conditions. The color fastness to light, rubbing, and washing of dyed 3D-printed TPU materials were investigated. At a 15 g/l glucose concentration and a 10 g/l calcium hydroxide concentration, the K/S value increased significantly, showing the color of the PB series. The K/S value tended to increase as dyeing temperature, dyeing time, and indigo dye concentration increased. However, the effect of indigo dye concentration was not significant, and there was no significant increase after the dyeing temperature was 90 °C and the dyeing time was 60 min. The color fastness to light was poor, but for washing and rubbing the fastness was good. Therefore, it was confirmed that more environmentally friendly 3D-printed TPU material dyeing is possible by indigo dyeing using glucose by replacing sodium hydrosulfite.