Absorption kinetics and thermodynamics of cationic dyeing for poly(ethylene terephthalate) copolyester modified by 2,2-dimethyl-1,3-propylene glycol (NPG)

Abstract

The copoly(ethylene terephthalate) (ENCDP) were successfully prepared with 2,2-sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate (SIPE), poly(ethylene glycol) (PEG) and 2,2-dimethyl-1,3-propylene glycol (NPG), named as cationic dyeable polyester. The dyeing properties consisted of adsorption kinetics and thermodynamics of cationic blue X-BL on the ENCDP fabric were investigated. The T-Vickerstaff hyperbolic adsorption model could be used to explain the adsorption kinetics and predict the equilibrium rate constant k, equilibrium dye sorption capacity (C∞), the half dyeing time (t1/2) and diffusion coefficient (D) at different temperatures. According to the adsorption activation energy (Ea)> 40KJ/mol, it is judged that the isotherm adsorption conforms to the langmuir isotherm and possessed the higher correlation. Moreover, the determined thermodynamic parameters including the positive value of adsorption affinity (-Δµ°) and enthalpy change (ΔH°) showed that the dye adsorption onto ENCDP was a chemisorption process of spontaneous and endothermic.