Surface Barrier Effects in Wool Dyeing Part I ‐ The Location of the Surface Barrier

Abstract

The properties of the surface layer on wool fibres which limits the rate of dye uptake have been examined. The removal of the barrier layer by mechanical means and its degradation by surface reduction using tri–butyl phosphine have been studied using the rate of dyeing as a parameter. The chemical properties of the barrier layer suggest that it is a cystine–rich component of the cuticle layer system, either the exocuticle or its ‘a’ layer sub‐system.

Lipid Role in Wool Dyeing

“…This investigation provided the first unequivocal evidence that dye does, in fact, enter the wool fiber between cuticle cells, and also showed that dye diffuses along the nonkeratinous endocuticle and CMC early in the dyeing cycle. The above finding supports the view that the cuticle (Makinson, 1968), probably the highly crosslinked A-layer of the exocuticle (Hampton & Rattee, 1979;Baumann & Setiawan, 1985), is a barrier to dye penetration, in that dyes are directed to the gaps between the scales in order to reach the cortex. It appears, however, that lipids present at the intercellular junctions are also a barrier to the diffusion of dyes into the nonkeratinous regions of the CMC (Leeder et al, 1985a).…”

Surface Barrier Effects in Wool Dyeing Part II – Studies of Surface Barrier and Bulk Diffusion Using a Radioactively Labelled Dye

“…The results described in Part 1 [ 1 ] have been confirmed by the tracer diffusion experiments and The results show also that the effect of phenolic compounds on the dyeing rate of wool is not restricted to either surface or bulk effects, but arises from their general swelling action on the fibres. The use of tracer diffusion measurement provides an unambiguous way of distinguishing between surface barrier and bulk diffusion effects in dye adsorption.…”

“…Fibre diameters, for the calculation of the diffusion parameters and the estimation of swelling, were determined as in Part 1 [1,9,10].…”

Low-temperature Dyeing of Wool Processed for Shrinkage Control

“…This layer is hydrophobic due to its lipid content and can act as a surface barrier to dye absorption and diffusion into the inner cortex. A continuous phase of membrane cells, the cell membrane complex (CMC) underneath the cuticle, forms a network of penetrating canals to help mediate the impedance of the lipid barrier to dye diffusion, thereby facilitating dye penetration into the fiber interior [8,10,14,19,22].…”