Development of technology to suppress the color fading of clothes while washing

The fashion industry has a significant environmental impact, due to the high carbon emissions and the short lifespan of clothing. We are approaching the reduction of clothing waste to improve its sustainability from laundry. According to our consumer survey, "color fading" was the main reason for discarding colored clothes. The survey also showed color fading was more likely to occur while washing. Therefore, this report describes a new technology for preventing color fading in laundry and its mechanism.

　We focused on fiber damage caused by repeated washing as one of the major causes of color fading. Surface observation by scanning electron microscope revealed "fibrillation", fiber splits axially and subdivides at about 10~50μm. This change increased with repeated washing and showed a good correlation with the results of visual appearance evaluation. This suggested the friction between clothes while washing affects color fading. To solve this problem, we investigated ways to reduce friction between clothes in water while washing.

　We hypothesized that the localization of agents on fabric surfaces during laundry can lead to reduced friction. We selected cationic surfactants, cationic polymers, silicones, and ester oils with different electrostatic properties and hydrophobicity as agents to promote adsorption to cotton. Logarithmic decrement, an indicator of friction properties, affected by each agent was evaluated by rigid pendulum-type physical property tester.

　As a result, specific cationic polymers showed a good friction-reducing effect, especially polymers with a polyethyleneimine structure showed a higher effect. The logarithmic decrement showed a good correlation with the color fading index ΔZ based on optical measurements. In addition, detergents with a low logarithmic decrement suppressed fibrillation and retained the color visually.
　Furthermore, we clarified the mechanism of friction reduction using Quartz Crystal Microbalance with Dissipation. The results suggested highly deformable adsorption layers are involved in the friction reduction effect.