An investigation of differences in the dyeing properties between wool fibres from various UK sheep breeds and the relationship with fibre structure and properties

  • Subhadeep Paul

Student thesis: Doctoral Thesis


Wool fibres, produced in the UK are predominantly coarse and have limited commercial applications and are often dumped or burned by UK farmers. The primary focus of this research was to study coarse wool fibres from different UK sheep breeds and find properties which can be exploited in innovative technical applications. As wool is a natural fibre it has variations in its physical and chemical properties. A review of the literature shows a previous comparative study of structure-property relationships of wool fibres from different breeds is limited. Wool fibre dyeing sorption and kinetics relate to the chemical reactivity of the fibre. The understanding of the factors responsible for changes in dyeing sorption can be utilised to manufacture technical textile products that are optimised for specific breeds. Wool from the fleece of four different breeds, Bluefaced Leicester, Greyface Dartmoor, Ryeland and Herdwick, were characterised to determine physical properties including mean fibre diameter, scale patterns and scale dimensions using Scanning Electron Microscopy (SEM). The dyeing behaviour (sorption) was investigated with Acid Red 1 and Leicester showed 7 % higher exhaustion than Dartmoor wool fibres (20% on mass of fibre). Herdwick and Ryeland both exhibited significant variation in their dye uptake at higher concentrations. Further investigations of dyeing thermodynamic and kinetic properties were performed to understand the influence of fibre surface morphology on dyeing behaviour. Dyeing equilibrium results of Acid Red 1 for both Leicester and Dartmoor wool fibres were fitted to Langmuir and Freundlich isotherms to calculate the theoretical maximum adsorption capacities of 164 and 144 mg/g respectively. The kinetics study showed an increase in diffusion coefficient of Acid Red 1 with the increase in mean fibre diameter of wool. Surface morphology studies found that the wool fibres demonstrated three different types of surface scale patterns. The total scale perimeter per 100 µm of fibre was calculated from the images and showed a polynomial correlation with the diameter of the fibre. The diffusion coefficient of Acid Red 1 showed a sigmodal increase with the increase in effective diffusion pathway (total scale perimeter per 100 µm) of the wool fibres. A hypothesised theory of scale opening gap was proposed to have affected the dyeing properties of wool fibre. To investigate the effect of the scale opening gap wool fibres were dyed using different acid dyes of varying molecular length of the dye. The time of half dyeing increased with the increase in molecular length of the dyes for all the wool fibres. The fibre dye uptake of the wool fibres decreases with the increase in molecular length of the dye molecules. This suggests surface morphology is one of the factors to be considered as the reason for the difference in dyeing properties between wool fibres, obtained from specific breeds.
Date of Award12 Mar 2024
Original languageEnglish
SupervisorParikshit Goswami (Main Supervisor) & Andrew Hewitt (Co-Supervisor)

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