A MECHANISTIC STUDY OF THE VAPOR PHASE COLORATION OF TEXTILES (POLYESTER)

The vapor phase transfer of disperse dyes from an ink film deposited on aluminum foil to a double-knit polyester fabric at 210(DEGREES)C has been investigated. Heat-transfer rates through the sample in different heating media have been determined. The molten-metal bath (with Wood's Alloy as the metal) has better heat transfer characteristics than many heating media used in the industry, such as thermosol ovens, perforated heated drums, etc. Replacement of transfer paper with aluminum foil does not significantly increase heating rates. However, the elimination of paper is desirable because paper is expensive and cannot be re-used indefinitely as can a metal support in the form of an endless belt.; Quantitative data have been obtained on the effect of vacuum on transfer rates. Furthermore, the dependence of the transfer rate on dye concentration in the ink film has been clearly established at different pressures. This dependence has been known for some time. However, the mechanistic implications of this observation have not been recognized by the available models. These models are also unable to properly explain the dependence of the transfer rate on ambient pressure.; Models have been presented for sublimation of dye particles from an ink film and for the diffusion of dye vapor into a porous fabric. Diffusion into the fabric has been considered as occurring with a simultaneous irreversible reaction (sorption) with the polymer and with an interfacial resistance offered by an air gap between the ink layer and the fabric.; The dependence of the transfer rate on dye concentration in the ink film and on the ambient pressure that is predicted by the model shows an excellent correlation with experimental data. Considering the fabric as being finite or semi-infinite seems to be of little consequence except under extreme conditions.