Thermodynamic and Kinetic Study on Eco-friendly Atmospheric Pressure Dyeing of Poly(Ethylene Terephthalate-co-Polyethylene Glycol) Fibers

Abstract

This study investigated the dyeability of poly(ethylene terephthalate-co-polyethylene glycol) (PCP) fibers engineered for convenient disperse dyeing, using both low and high energy disperse dyes within a temperature range of 90–130 °C. A thermodynamic analysis revealed that the disperse dyeing of PCP fibers followed the Nernst isotherm. It displayed higher partition coefficients and equilibrium exhaustion than those of conventional PET fibers. The affinity parameter indicated a higher affinity of the disperse dyes for the PCP fibers, although the enthalpy and entropy variation indicated weaker dye embedding within the PCP polymer matrix. Kinetic studies revealed that dye exhaustion occurs more rapidly on PCP fibers at a temperature below the conventional disperse dyeing temperature for polyester (i.e., below 130 °C). In addition, the PCP fibers exhibited lower dyeing transition temperatures and higher diffusion coefficients at these reduced temperatures. Among the studied dyes, the low-molecular-weight disperse dye demonstrated more favorable thermodynamic and kinetic parameters than the high-molecular-weight disperse dye. Overall, these observations indicate that dyeing at 100 °C under atmospheric pressure is the optimal process condition for PCP fibers and is effective for both low- and high-molecular-weight dyes.