Preparation and characterization of cotton fiber fragments from model textile waste via mechanical milling and enzyme degradation

Rather than landfilling or incineration, value exists in textile wastes that should be recovered. Cotton is a major component of apparel and other textile materials that could find new value by extracting it from textile waste in the form of cotton fiber fragments (CFFs). To explore this potential, CFF properties were analyzed and compared after producing them from model undyed and fiber reactive dyed textile waste fabrics by mechanical milling or enzymatic degradation. Characterization methods included scanning electron microscopy (SEM), optical microscopy, fiber quality analysis, degree of polymerization (DP), X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Enzyme-treated undyed CFFs exhibited distinct properties of flattened fiber fragment dimensions, a more uniform fiber length distribution compared to other CFFs, a DP comparable to solvent-spun regenerated cellulose fibers from cotton, the highest crystallinity of all CFFs tested, greater hydrophobicity than milled cotton reference material, and better thermal stability than milled reference cotton. The effects of mono-functional and bi-functional reactive dyes on enzyme degradation behavior and final product characteristics were also evaluated and discussed. Both dyed and undyed CFFs show good potential for being utilized in diverse applications. This analysis of the properties of partially degraded cotton fibers provides a necessary technical foundation for promoting CFF recycling for use in applications such as composites and regenerated fibers, and provides insights on the mechanism by which cotton disintegrates in the presence of enzymes to potentially inspire new strategies for dyeing cotton that takes a designed for recycling perspective into account.