Study on the simultaneous release of microfiber and indigo dye in denim fabric home washing

In recent years, with the increasing global focus on environmental protection, the issue of microfiber release from denim during the washing process has gained attention. In this study, a programmable washing device simulating household drum washing was designed and developed, microfibers and indigo dyes released from denim washing were quantitatively detected, and we have also developed a novel method for estimating the release of microfibers during washing. The effects of washing time, washing temperature, and washing load on microfiber and indigo dye release from denim were explored. The results showed that the effect of washing load on microfiber and indigo dye release was greater than washing temperature and washing time. The research findings indicate that with an increase in washing time (35-95 min) and washing load (100-250 g), the shedding of microfibers and indigo dye significantly increases, reaching peak release levels of 343.6 μg/g fabric and 0.027 mg/L, respectively. However, there is a decreasing trend in the release of microfibers and indigo dye when the washing temperature exceeds 50 °C. Furthermore, our data suggests that an increase in washing load leads to a significant change in the number of microfibers (from 978 items/g fabric to 1997 items/g fabric) and their mass (from 156.87 μg/g fabric to 343.56 μg/g fabric). The influence of washing time, washing temperature, and washing load on microfiber length shows relatively small fluctuations within the range of 600-900 µm. This study provides new ideas and methods for estimating the release of microfiber and indigo dye in denim washing around the world.