To investigate the contributions of polymer relaxation phenomena to the mechanism of disperse dye adsorption on poly(ethylene terephthalate) fibres, a commercial grade dye was applied to poly(ethylene terephthalate) fabric at temperatures between 30°C and 130°C. Three regions of temperature‐dependent dyeing behaviour were identified, in which the promotional effect imparted by increasing dyeing temperature varied, depending on whether dyeing had been carried out at temperatures that were below, within or above the polymer's glass transition temperature, Tg, namely < 65°C, between 65°C and 110°C and between 110°C and 130°C, respectively. When experimentally determined colour strength data points (log 1/fk) were fitted to plots of polymer structural relaxation (log aT) calculated using the Williams, Landel and Ferry equation as a function of (T − Tg), three different levels of correspondence were achieved which paralleled the observed three regions of temperature‐dependent dye uptake. The adsorption of the commercial disperse dye on the poly(ethylene terephthalate) fibre therefore concurs with the free volume model of dye diffusion insofar as the diffusional behaviour of the dye is related to the relaxation time of the molecular motions occurring within the poly(ethylene terephthalate) polymer. The finding that the poly(ethylene terephthalate) substrate's glass transition extends over a broad range of temperature upto ~110°C explains why elevated dyeing temperatures in the region of 130/140°C must be used in High Temperature dyeing processes, and also, why ~75% of uptake of the commercial disperse dye on the poly(ethylene terephthalate) fabric occurs over the very narrow 20‐30°C critical temperature range between 110 and 130°C/140°C.
This review concerns the application of dyes to both natural and man‐made cellulosic fibres from aqueous dyebaths using exhaust dyeing processes and the role of added inorganic electrolyte in such dyeing systems. This part of the article presents a review of the fundamental properties and characteristics of cellulosic fibres and each of the five classes of dye employed for their coloration, as well as the essential principles involved in the application of the various types of dye to cellulosic fibres. In the next part of the article, the various theories and concepts which have been proposed to account for the promotional effect exerted by added inorganic electrolyte on dye uptake are reviewed and scrutinised, from the viewpoints of the essential physico‐chemical properties of the five classes of dye that are used and the fundamental aspects of their application.
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