The roles of polymer relaxation phenomena, aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: Part 4 further aspects related to polymer relaxation phenomena

Abstract

To further investigate the contribution of polymer relaxation times to the mechanism of disperse dye adsorption on poly(ethylene terephthalate) fibres, the temperature‐dependent uptake of Teratop Yellow HL‐G 150% on both cotton and polyamide 66 fabrics at temperatures between 30 and 130°C was compared with that on poly(ethylene terephthalate) fabric. Although uptake of the commercial grade dye on polyester fabric is governed by the thermally regulated, broad glass transition of the water‐saturated poly(ethylene terephthalate) substrate, as this was not observed for either cotton or nylon 66 fabrics, the respective cellulose or polyamide 66 polymer glass transition does not present a major thermal impediment to dye uptake over the wide range of dyeing temperatures used. This is because the onset and end‐set temperatures of the glass transition of the water‐plasticised poly(ethylene terephthalate) material reside within the range of dyeing temperatures employed, whereas those of the water‐plasticised cotton and polyamide materials occur below the lowest dyeing temperature examined (30°C). The thermal dependency of disperse dye solubility also likely makes a meaningful contribution to the temperature‐dependent dye uptake observed for each type of fibre.

The roles of polymer relaxation phenomena, aqueous dye solubility and the physical properties of water in the mechanism of adsorption of a disperse dye on poly(ethylene terephthalate) fibres: part 5 analysis of polymer relaxation phenomena for different polymers

“…Although very similar dye uptake versus temperature profiles were secured for all three types of fabric when dyeing had been undertaken at temperatures above the endset temperature of the glass transition of the respective water‐plasticised fabric, namely, ≦ 30°C in the case of both cotton and PA 66 and 110°C for PET, the dyeing temperature profile obtained for PET fabric differed considerably to that of its cellulosic and nylon fabric counterparts in the case of dyeing temperatures that were below the endset temperature of the PET glass transition (ie < 110°C) 1 …”

“…The previous part of the study 1 showed that when the commercial grade disperse dye Teratop Yellow HL‐G was applied to cotton, polyamide 66 (PA 66) and poly(ethylene terephthalate) (PET) fabrics, over the broad range of dyeing temperatures between 30 and 130°C, the temperature dependent uptake of the dye on each type of substrate concurred with the fundamental premise of the free volume model of dye diffusion, insofar as, dye uptake was observed for all dyeing temperatures that were above the onset temperature of the glass transition of the respective water‐plasticised cellulosic, nylon 66 or polyester substrate, namely cotton = 0°C, PA 66 = −10°C and PET = ~65°C, this particular thermal transition parameter being referred to as the fibre's wet T g.…”

“…To explain these findings, it was proposed 1 that under the high‐temperature (HT) dyeing conditions used, because dye uptake is governed by thermally activated macromolecular relaxation processes occurring within the respective cotton, PA 66 or PET fabric, in which the glass transition of the particular polymer assumes a principal role, the observed differences in the temperature dependent extent of uptake of the commercial dye achieved on the three fibre types can be attributed to the different temperature range over which the respective, water‐plasticised, cellulose, nylon 66 or PET polymer glass transition presents a thermal impediment to dye diffusion. Accordingly, the glass transition of the water‐plasticised cotton and PA 66 substrates did not present a thermal barrier towards dye uptake because the very low onset and endset temperatures of the respective polymer glass transition do not occur within the 30–130°C range of dyeing temperatures examined [ie onset (endset) temperature/°C: cotton = 0 (< 30); PA 66 = −10 (< 30)].…”

“…These findings were assumed 1 to imply that either the same of very similar mechanism of adsorption applies in the cases of the aqueous Teratop Yellow HL‐G/cotton, Teratop Yellow HL‐G/PA 66 and Teratop Yellow HL‐G/PET fibre dyeing systems. In turn, this suggests that not only must the nature of the dye–fibre interactions operating between the commercial grade disperse dye and the cellulosic, nylon and polyester substrates be very similar or even identical, but also, at dyeing temperatures above the endset temperature of glass transition, similar thermally dependent molecular rearrangements within the respective cellulose, PA 66 or PET polymer are responsible for the observed temperature dependent diffusional behaviour of Teratop Yellow HL‐G within the cotton, PA 66 and PET materials.…”

“…Although the intrinsic connection between the thermally regulated relaxation times of polymer chain segmental mobility responsible for the glass transition of PET fabric and the thermally governed uptake of the commercial dye on PET fabric was previously established using the Williams–Landel–Ferry (WLF) equation, 3 confirmation of the linkage between thermally activated uptake of the dye on cotton and PA 66 fabrics and the relaxation times of the molecular relaxations taking place within the respective cellulosic and PA 66 fabrics has not as yet been established 1 …”