The influence of dyes on the mechanical properties of composites fabricated from waste polyester/cotton fibers and their potential application value in the construction field

The waste of a significant quantity of poly-cotton textiles contributes to environmental pollution, making recycling an urgent necessity. This study employed Dimethyl sulfoxide (DMSO), Sodium Hydrosulfite (Na₂S₂O₄), and NaOH for the decolorization of waste polyester/cotton fabric, followed by the preparation of fiber-reinforced composites through a hot pressing process. Notably, no additional resin was incorporated as a matrix material during this process. The study systematically investigated the influence of reactive dyes and vat dyes on the mechanical properties of the composites before and after decolorization. The results revealed that the mechanical properties of reactive dye-dyed fiber composites (RDFC) were significantly inferior to those of undyed fiber composites (UDFC) and decolorized fiber composites, with reductions ranging from approximately 9.76 %–407.72 %. In contrast, the mechanical properties of vat dye-dyed fiber composites (VDFC) exceeded those of UDFC and decolorized fiber composites, showing improvements between 1.1 % and 29.61 %. Under wet conditions, all types of fiber composites exhibited a mechanical property loss of approximately 20 % after decolorization, indicating that the influence of moisture is manageable. Furthermore, the strength of these composites was found to be comparable to traditional materials such as gypsum boards and logistics wood pallets, among other applications. These findings highlight the potential of these materials as sustainable, high-performance alternatives in construction and related fields, offering significant application value and environmental benefits.