Fiber Processing

The topmaking performance of fleeces from sheep that were ranked high or low on index selection using objective measurement was compared with that of sheep from the same flock that were ranked high or low on visual assessment. A flock of 451 15-month-old fine-wool Merino sheep were classed by 2 experienced fine-wool sheep classers into 3 grades: best, average and culls. Forty-four sheep were assessed as ‘best’ and 77 sheep were graded as ‘culls’ by both classers. These sheep were defined as the ‘best visual’ and ‘worst visual’ sheep, respectively. Measurements of clean fleece weight, mean fibre diameter, coefficient of variation of fibre diameter and body weight were used in a selection index to rank all sheep in the flock. The selection index was designed to rapidly reduce mean fibre diameter and slowly increase clean fleece weight, whilst maintaining staple strength and body weight. The 44 sheep with the highest index value were defined as ‘best index’ sheep and the group of 77 sheep with the lowest index or obvious physical faults were defined as the ‘worst index’ sheep. Twenty-five fleeces were randomly selected from each of the ‘best’ and ‘worst visual’, ‘best’ and ‘worst index’ sheep for individual processing through to top. The fleeces from the ‘best index’ sheep produced greater quantities of tops that were significantly finer, longer, of lower curvature and produced less noil than all other groups. In contrast to the large difference in quality between tops from the ‘best’ and ‘worst index’ sheep, there was little difference in quality between tops from the ‘best’ and ‘worst visual’ sheep. This indicates that the traditional wool producer views of wool quality are unrelated to processing performance. It was concluded that Merino sheep selected by index selection using direct measurement of fleece weight, mean fibre diameter and coefficient of variation of diameter as selection criteria produced greater quantities of wool of superior processing performance to that from sheep selected using visual assessment. more »

A benchtop scouring procedure was used to evaluate the ability of conventional detergent scouring systems to adequately clean fleece samples from a selection of Western Australian Merino wools. Sixteen fleeces were selected from the Western Australian Department of Agriculture resource flocks, covering a wide range in yield (49.2 to 77.5%), wax (7.3 to 26.9%), suint (4.9 to 11.6%), and dust (1.4 to 16.3%) contents. Using a simple detergent-based system, 50% of the fleeces were classified as effectively scoured, based on residual wax content. When scouring liquor was not refreshed between subsamples drawn from the same fleece, wool wax, staple length and dust content in the greasy fleece accounted for 93% of the variation in the rate of residual wax increase observed in sequential 10 g samples of wool. Residual ash content also increased but the greasy fleece parameters measured were not statistically significant predictors of residual ash changes. The rate of scoured wool colour change, when sequential samples of greasy wool from the same fleece were scoured without liquor change, could be predicted from greasy fleece yields. The scouring efficiency of the more difficult to scour wools was improved by the addition of sodium carbonate to the main scouring bowls. more »

Felting of wool is a major problem in the manufacture of knitted and woven products, as it is related to yarn shrinkage, which is a critical problem of the finished product. Felting is a unique property of animal fibres and a desirable characteristic in the making of felted products. However, felting is a particular problem with fine wools. Non-shrink woollen products are currently produced using chemical treatments during processing. Chlorination is the first step and it degrades the fibre surface. Fibres are then coated with polymers to cover degraded scale structures and/or to bond fibres together to prevent felt shrinkage. This process minimises frictional effects on wool fibre surfaces, limits relative motion of fibres in all directions, and increases hydrophilic properties of the fibre surface (Chen et al., 2000). Although these processes have been highly successful in shrink-proofing wool, they are expensive and detrimental to the fibre. Furthermore, the chlorination process is environmentally unfriendly and there are difficulties with residue disposal. Greeff and Schlink (2001) have shown that felting is a heritable trait, which implies that altering the ability of wool to felt through breeding may make a considerable contribution to wool’s processing properties and will enhance wool’s clean and green image. However, felting is strongly influenced by fibre curvature, fibre diameter (Scheepers and Slinger, 1968 ; Hunter et al., 1982 ; Kenyon et al., 1999 ; Veldsman and Kritzinger, 1960) and clean yield (Schlink et al., 2000). Lipson and Rothery (1975) showed that Merino wool has a significantly higher felting ability than Polwarth wool in spite of the fact that there were no differences in fibre surface friction, scale frequency or elastic properties between the breeds.They did note significant differences between the breeds in “swellings and necks” at intervals along the fibres, but conclusions were not clear because these wools differed in micron and curvature was not recorded. The OFDA2000 (Brims, 1997) has algorithms to measure variability and unevenness traits along the fibre which may be used to identify samples that may cause spinning problems. The objective of this study was to identify whether these along fibre variability traits influence felting and whether they are heritable. more »