The plasticisation model of dye diffusion: Part 5

Abstract The findings presented in the previous part of the paper (Part 4) of the re‐evaluation of previously published data reported for the temperature‐dependent diffusion of an organic acid within nylon 6 film, desorption of three acid dyes from dyed nylon 66 fabric, diffusion of an acid dye within nylon 6 monofilaments and adsorption of a sulphur dye onto nylon 66 fabric, were analysed. The differentiation of the temperature‐dependent dyeing/desorption behaviour of each of the six anionic compounds into two distinct, but interconnected, thermal regions, which corresponded to diffusion/desorption/adsorption undergoing a marked change at either 50, 60, or 70°C, was attributed to the broad, overlapping glass transition of the mobile amorphous and rigid amorphous phase components. As the experimentally observed diffusion/desorption/adsorption of each of the six types of anionic species adhered to a Williams–Landel–Ferry relationship, their thermally activated dyeing/desorption behaviour is governed by the thermally regulated relaxation times of the structural rearrangements occurring within the water‐plasticised polyamide material. The plasticisation model of dye diffusion seems to offer a reasonable explanation of the observed temperature dependency of the diffusivity of the organic acid, each of the four acid dyes and sulphur dye within the different types of aliphatic polyamide substrate.