The Causes of Anomalous Results in the Measurement of Wool Fibre Swelling

Abstract

The causes of anomalous results obtained in the measurement of the swelling of wool fibres by different methods have been investigated. The British Standard method (BS 2043) and the fixed‐point method were examined. When urea solutions are used as the swelling media, the results obtained by the two methods differ considerably. The short lengths of fibre used in the BS 2043 method are well within the fibre dimensions for swelling to occur by end penetration and hence give results that can be misleading when related to the swelling of undamaged fibres during processing. When the swelling agent itself can penetrate the fibre wall, either method will give reliable results. When, however, the agent can show colligative osmotic properties typical of many non‐volatile salts, discrepancies may arise between the two methods.

Adsorption of Urea and Thiourea by Wool

“…The results reported here suggest that there is good penetration of urea and thiourea into wool fabric, in contrast to a recent report relating to single fibres [6].…”

Book review

“…Numerous articles have been published on the interaction of urea with dyes and keratin fibers 2–9. The function of urea in low temperature dyeing is considered to be disaggregation of anionic dyes,2 swelling of wool,3, 4 and removal of a part of the hydrophobic material from the surface of the cuticle layer 5, 6. However, the actual function of urea cannot be clarified because of the complexity of its mechanisms.…”