Enhancing dyeability of sustainable polylactic acid fabrics through cross-sectional modification of filaments

Polylactic acid (PLA) fiber, renowned for its renewable and biodegradable nature, is increasingly recognized as a promising alternative to conventional polyethylene terephthalate (PET) polyester fiber in the textile industry. However, the poor dyeability of PLA has limited its widespread industrial application. This study aims to enhance the dyeability of PLA fabrics by modifying the cross-sectional shape of PLA filaments and optimizing the dyeing conditions for disperse dyes. PLA filaments with circular, cruciform, and trilobal cross-sections (designated as PLAO, PLA+, and PLAY, respectively) were fabricated and then knitted into fabrics. Dyeing experiments using three different disperse dyes consistently demonstrate that PLA+ fabrics exhibit the best dyeing performance, followed by PLAY fabrics, with PLAO fabrics showing the lowest effectiveness. These results highlight the significant effect of filament cross-sectional shape on dyeing performance. Further macroscopic and microscopic analyses indicate that profiled PLA+ and PLAY filaments possess higher non-roundness factors and specific surface areas, lower glass transition temperatures, and reduced crystallinity, collectively enhancing their dyeability. In addition, lower fabric luster contributes to achieving deeper color. The study also identifies the optimal dyeing conditions for PLA fabrics with the selected disperse dyes: pH 5.0, dye concentration of 4% owf, dyeing temperature of 110°C, and dyeing time of 30 minutes. Under these optimized conditions, PLA+ and PLAY fabrics exhibit significantly enhanced K/S values, while dyeing levelness and color fastness across all PLA fabrics remain within acceptable ranges.