Waterless dyeing of polylactic acid with disperse dyes using decamethylcyclopentasiloxane as medium

Polylactic acid (PLA) fibre as a new generation of eco-friendly polyester fibre is expected to substitute polyethylene terephthalate (PET) fibre to be an important textile fibre raw material. However, there exist severe strength loss and light dyeing colour by the traditional water bath dyeing method, which seriously affect the promotion and application of PLA fibre in the textile fields. Therefore, it is necessary to study waterless dyeing method for PLA. Decamethylcyclopentasiloxane (D5) possesses excellent physical and chemical properties with the characteristics of odourless, non-flammable, and stable to various chemicals, which has been studied to be used as a waterless dyeing medium for PET fabric. In this study, D5 was selected as the medium to study the waterless dyeing process and properties for PLA. The effects of disperse dye dosage, dyeing temperature, dyeing time and liquor ratio on the dyeing properties of PLA fabric were investigated. The results showed that the optimal dyeing process conditions were as follows: the dye dosage was 4%, dyeing temperature and time were 120°C and 40 min, respectively, and the liquor ratio was 1:10. Then PLA was dyed by three different colour disperse dyes using the optimal process which were compared with the traditional water bath. The results showed that the properties of dyed PLA fabrics with D5 could reach the dyeing effect of the traditional water bath method, while causing less influence on its mechanical property. Therefore, this research proved that D5 can be used as a dyeing medium for PLA fabric to substitute the traditional water bath dyeing.