Sustainable dispersant-free dyeing of poly(lactic acid) with microbial prodigiosins in decamethylcyclopentasiloxane (D5) medium

Abstract

Traditional poly(lactic acid) (PLA) dyeing with synthetic disperse dyes in water medium presents a significant environmental risk since it consumes a large amount of chemicals and generates dyeing wastewater. In order to comply with the demands of clean production and sustainable development, a dispersant-free solvent dyeing system was developed by employing decamethylcyclopentasiloxane (D5) as dyeing medium and microbial prodigiosins prepared through surfactant-assisted fermentation as natural disperse dye. The influence of D5 medium on PLA fiber and prodigiosins was investigated. It was discovered that D5 could swell PLA fibers by penetrating the inside of the fibers while having no adverse effects on prodigiosins. The dyeing parameters were subsequently optimized in terms of K/S value and strength loss. The results indicated that PLA fabrics dyed in a modified solvent dyeing system containing 250% (owf) water exhibited the highest K/S value and minimum strength loss when they were dyed at dyeing temperature 105 °C, aqueous pH7.0 and dyeing time 30 min. The colorfastness of solvent dyed fabrics were equivalent to that of aqueously dyed fabrics in terms of rubbing and washing. The solvent dyeing process developed in this study effectively reduces the consumption of dispersant agents, being conducive to facilitate the further development of sustainable PLA industry.