Reducing dye pollution: Sustainable reuse of colored cotton waste powders in washing-free flat screen printing

To alleviate environmental pollution and resource scarcity pressures, this study focuses on two key challenges in the textile industry: achieving water free printing of fabrics and recycling of waste textiles. Recycling and grinding colored waste cotton textiles into cotton fiber powder (testing the particle size distribution, morphology, crystal structure and thermal stability of cotton powder). By adjusting the type and quality of water-based polymers, different washing-free printing pastes are prepared. The printing pastes were used for screen printing on cotton fabrics. The key research content of this study is as follows: Low field nuclear magnetic resonance (LF-NMR) and biological microscopy were used to reveal the water distribution state (bound water, free water) and the microstructure (three-dimensional network structure) in the printing pastes. The rheological properties of the printing pastes were tested and analyzed using a rheometer (non Newtonian fluid). A comprehensive performance evaluation was conducted on printed fabrics, including sharpness, color strength, and color fastness. The absorbance (UV), chemical oxygen demand (COD), and biochemical oxygen demand (BOD₅) of the washing solution for printed cotton fabrics were tested. In summary, this study successfully utilized recycled colored waste cotton powder to prepare washing-free printing pastes suitable for flat screen printing of cotton fabrics; The comprehensive evaluation of printed fabric performance indicated that sample 2 had the excellent printing effect; The washing solution for red, yellow, and blue printed cotton fabrics contains very little colored cotton powder and has extremely low oxygen consumption. This technology can effectively reduce water pollution and resource consumption.