Tag: "fiber"

  • Wool Fibre Crimp is Determined by Mitotic Asymmetry and Position of Final Keratinisation and not Ortho- and Para-cortical Cell Segmentation

    Crimp, a distinguishing feature of sheep fibres, significantly affects wool value, processing and final fabric attributes. Several explanations for fibre bending have been proposed. Most concentrate on relative differences in the physicochemical properties of the cortical cells, which comprise the bulk of the fibre. However, the associations between cortical properties and fibre crimp are not consistent and may not reflect the underlying causation of fibre curvature (FC). We have formulated a mechanistic model in which fibre shape is dictated primarily by the degree of asymmetry in cell supply from the follicle bulb, and the point at which keratinisation is completed within the follicle. If this hypothesis is correct, one would anticipate that most variations in fibre crimp would be accounted for by quantitative differences in both the degree of mitotic asymmetry in follicle bulbs and the distance from the bulb to the point at which keratinisation is completed. To test this hypothesis, we took skin biopsies from Merino sheep from sites producing wool differing widely in fibre crimp frequency and FC. Mitotic asymmetry in follicle bulbs was measured using a DNA-labelling technique and the site of final keratinisation was defined by picric acid staining of the fibre. The proportion of para- to ortho-cortical cell area was determined in the cross-sections of fibres within biopsy samples. Mitotic asymmetry in the follicle bulb accounted for 0.64 (P < 0.0001) of the total variance in objectively measured FC, while the point of final keratinisation of the fibre accounted for an additional 0.05 (P < 0.05) of the variance. There was no association between ortho- to para-cortical cell ratio and FC. FC was positively associated with a subjective follicle curvature score (P < 0.01). We conclude that fibre crimp is caused predominantly by asymmetric cell division in follicles that are highly curved. Differential pressures exerted by the subsequent asymmetric cell supply and cell hardening in the lower follicle cause fibre bending. The extent of bending is then modulated by the point at which keratinisation is completed; later hardening means the fibre remains pliable for longer, thereby reducing the pressure differential and reducing fibre bending. This means that even highly asymmetric follicles may produce a straight fibre if keratinisation is sufficiently delayed, as is the case in deficiencies of zinc and copper, or when keratinisation is perturbed by transgenesis. The model presented here can account for the many variations in fibre shape found in mammals. more »
  • Wool Fiber Properties and Wool Quality Number

    Wool fiber: Like all other protein fibers, wool is also derived from the animal hair. Wool is mainly used as a minor blend (up to 10%) with cotton to introduce special properties to the terry fabric. Raw wool contains a wide variety of impurities, which can account for between 30% and 70% of the total mass. The impurities consist of wool grease, secreted from the sebaceous glands in the skin; suint, produced from the sweat gland; dirt and sand. Wool grease consists chiefly of esters, formed from a combination of sterols and aliphatic alcohols with fatty acids. Suints consist primarily of the potassium salts of organic acids. more »
  • Macro and Micro Structure of Wool Fiber

    The crimped configuration prevents wool fibers from aligning themselves too closely when being spun into yarn. As a result it is possible to have wool textile materials with air spaces. Occupying about two-third of the volume. The warmth of wool fabric is due more to the air spaces in the material then to fiber. more »
  • Relationship of Ortho-Cortex to the Crimp Wave in a Double-Crimped Wool

    The cortex of a crimped Merino wool fibre comprises two hemi-cylinders, which differ in both chemical and physical properties. The form of the crimp wave is related to alternations in the positions of the two cortical components within the fibre—the ortho- and the para-cortex1–4. The ortho-cortex tends to lie on the convex aspect of the crimp wave and the para-cortex on the concave aspect. more »
  • Alpaca – Leading the Way?

    Alpaca numbers in Australia are estimated to be between 170,000 and 450,000, with the higher estimate considerable in view that the sheep flock only numbers around 70 million. Wool ranging from 24 through to 26.8 micron is blended with alpaca. The combination of alpaca numbers and some relationship of the alpaca fibre to wool are behind this brief look into this ancient luxury fibre. more »

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