Sustainable and hydrolysis-free dyeing process for polylactic acid using nonaqueous medium

A sustainable and hydrolysis-free dyeing process was developed for polylactic acid (PLA) fibers. PLA is a biobased alternative to petroleum based polyethylene terephthalate (PET), which is the most widely used textile fiber. However, the hydrolytic degradation of PLA fibers under the conventional aqueous dyeing conditions limited its applications in textile industry. A new solvent dyeing process was developed using liquid paraffin as a nonaqueous dyeing medium. High quality dyed PLA fabrics were obtained without consuming water and auxiliaries. Minimal strength loss of dyed fibers was achieved by postheat setting treatment. The 3R principle (reduce, reuse, and recycle) was implemented to ensure the environmental friendliness of solvent dyeing process. The result of a 9-cycle reuse sequence demonstrated excellent color consistency of dyed PLA fabrics. The sustainability of our new dyeing process was quantified in the framework of environmental-health-social impact. The dyeing process sustainability index indicated that the solvent dyeing process was preferred over the aqueous dyeing. The method developed in the present work enabled the practical applications of PLA as textile fibers. It represented an important step toward a sustainable textile industry.