Low temperature solvent dyeing of synthetic polymers: A solubility parameter approach

Polymer-dye-solvent interactions were studied, and selected solvent mixtures were used for rapid dyeing of synthetic polymers at low temperatures. In the course of the study, 3-Dimensional Solubility Parameter theory was used to predict the dyeing behavior of poly(vinyl chloride) (PVC), Nylon 6,6, polyethylene(terephthalate) (PET), and polyethylene films using eight 1,4-disubstituted anthraquinone dyes in various solvent mixtures. Hansen parameters were further modified by combining the polar and hydrogen bonding parts under a single parameter called "Associative Solubility Parameter",{dollar}deltasb{lcub}rm a{rcub}{dollar}. Associative solubility parameters of dyes were determined by a newly developed TLC method.; From several experiments with different solvent systems, 75/24/1 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113)/Methanol/Water v/v/v solvent mixture was found to be the most effective for dyeing PVC and Nylon 6,6. With this system, it was possible to dye PVC and Nylon films at 40{dollar}spcirc{dollar}C reflux temperature over short dyeing times, which cannot be accomplished using conventional methods. Polyethylene was only slightly dyeable using this system as expected. Another set of experiments resulted in 70/30 Freon 113/monochlorobenzene v/v solvent system which dyed polyester successfully at about 50{dollar}spcirc{dollar}C reflux temperature in 30 minutes.; Dyeing rate curves were sigmoidal in shape, suggesting variable surface concentrations of dyes on the films. Dye concentrations on substrates were determined using both Kubelka-Munk K/S values and spectrophotometric methods. The diffusion coefficients and equilibrium concentrations of dyes on PVC were calculated by means of Crank's equation solved for variable surface concentration. The dyes with {dollar}deltasb{lcub}rm a{rcub}{dollar} values very close to that of the corresponding polymer showed maximum dyeing rates. Plots of dye uptake versus {dollar}deltasb{lcub}rm a{rcub}{dollar} of the dyes showed Gaussian-like distributions having maxima matching the {dollar}deltasb{lcub}rm a{rcub}{dollar}'s of dyes and films. As a result, dyeing behavior of all film samples were shown to be dependent on the {dollar}deltasb{lcub}rm a{rcub}{dollar} values of dyes and polymers.; It was also proposed that plasticization of PET by solvents was governed by dispersive interactions, since thermomechanical analysis findings combined with the results of dyeing experiments showed that PET was most plasticized and dyeable in the solvent mixture that had the same disperse solubility parameter, {dollar}deltasb{lcub}rm d{rcub}{dollar}, as PET.