The effect of ellipticity of wool fibres on handle assessment : A dissertation submitted in partial fulfilment of the requirement for the Degree of Bachelor of Agricultural Science with Honours at Lincoln University

Abstract

Wool is the most commonly used animal fibre, with clothing considered the high-value end-use. The mean fibre diameter (MFD) is the most important attribute in determining the value of a wool lot. In apparel, the handle of a fibre or fabric can influence consumer satisfaction, and therefore it is an important attribute to consider when producing wool fibre that is ‘fit for purpose’ and in demand by the textile industry. However, the handle assessment of wool fibre is subjective, and there is no objective measurement available. The MFD is known to account for some, but not all, of the variation in wool handle assessment. Consequently, there is a research focus on other fibre attributes that influence the handle of wool fibre, such as fibre shape. Wool fibres are not often circular in cross-section, and the degree of ellipticity of a wool fibre cross-section is called the fibre contour. This research was undertaken to see if fibre contour affected the fibre handle or the diameter distribution for Merino and NZ Romney ram wool samples. A greasy wool measurement system called FibreScan was used in the commercial testing of all the wool samples, but only the Merino wool samples were used in the handle assessment analysis. The results suggest there is a weak correlation between the contour ratio of a Merino wool sample and the handle assessment, but that it was not significant at a 95% confidence level. The MFD was the only variable included in a regression model that could be used to predict handle assessment of a fibre sample, and MFD explained 34% of the variation in handle assessment. Variation in the handle assessment by assessors highlighted the complexities of trying to produce an objective measurement to predict the handle of wool fibres for consumers. High contour ratios for NZ Romney ram wool samples produced fibre diameter distribution histograms that were bimodal in appearance, but the Merino samples did not. The absence of bimodality for Merino sample fibre diameter, suggests that as MFD decreases, it influences the visual distribution of fibre diameter around the mean. Overall, the results suggest that contour ratio has a minor effect on handle assessment of fine wool. Contour ratio affects the distribution of fibre diameter in strong wool samples but not fine wool, suggesting that MFD has an overriding effect on the results of this experiment.