38—the Intracellular Structure of the Wool Fibre

Speakman, J. B.

doi:10.1080/19447022708661427

Cited by 93 publications

(41 citation statements)

References 6 publications

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“…6) beyond the Yield region with the mechanically stiffer behavior of the fiber up to break defines the Post-Yield region. Speakman 25 showed that, for extensions within the Yield region at room temperature, the mechanical properties of the fibers were completely recovered after release of these fibers in water for a period of approximately 20 h. Astbury 26 concluded from his high-angle x-ray diffraction measurements that the Yield region was the result of extension in an amorphous region of the ␣-keratin structure. He proposed that the stiffening of the fiber, when extended into Post-Yield region, was due to the unfolding of the organized crystalline structure from the folded ␣-configuration to the extended ␤-state.…”

Section: The Yield Regionmentioning

confidence: 97%

Natural protein fibers

Feughelman

2001

J of Applied Polymer Sci

114

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Alpha keratin fibers (hairs, wools, quills, and other mammalian appendages) together with fibroin fibers such as silks and spiders webs are all highly extensible fibrous proteins for which the mechanical properties are of primary importance both to the animal from which they originate and their ultimate application by man. Similarly, the collagens are highly inextensible fibrous proteins, which form the major component of mammalian skin and connecting structures such as tendons. All these fibrous proteins are biological polymers of polypeptide chains for which the mechanical and allied physical properties, such as water absorption, relate to both their macrostructure and their molecular and near-molecular structure. Because of both their commercial application and their relatively complex structure at the molecular and near-molecular level, interpretation of the physical properties of ␣-keratin fibers represents the main component of this presentation. The mechanical properties of ␣-keratin fibers are primarily related to the two components of the elongated cortical cells, the highly ordered intermediate filaments (microfibrils) which contain the ␣-helices, and the matrix in which the intermediate filaments are embedded. The matrix consists of globular proteins plus water, the content of the latter being dependent on the fibers environment. The Extended Two-Phase Model (ETPM) has been developed and results in a detailed coverage of the bulk mechanical properties of ␣-helical fibers in terms of their known molecular and near-molecular structure. The inextensible protein fibers, the collagens and fibroins, are also briefly discussed in terms of the relationship between mechanical properties and the structure of these fibers.

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Section: The Yield Regionmentioning

confidence: 97%

Natural protein fibers

Feughelman

2001

J of Applied Polymer Sci

114

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“…Speakman's [5] observation that the ke ratin fibers which are extended no furthe r than the yield region have the ability to recover fully their propert ies when relaxed in water proved of exceptional value in assessing simply and accurately the changes in fiber properties associated with chemical or physical treatment of hair. His technique involves determination of work required to stretch the hair 30% (calibration step) followed by overnight relaxation in water, subjecting the fiber to intended treatment and re-stretching.…”

Section: Tensile Propertiesmentioning

confidence: 98%

“…By setti ng or waving of hair, helical coil configurations are formed and their performance can be viewed in the light of the engineering spring theory with respect to the effect of coil radius, its torsional stiffness and the hair diameter . Two general approaches have been used to measure torsional properties of hair fibers: the direct twist method of Morton Also, a "calibration" step similar to that used by Speakman [5] in tensile measurements is possible, and thus the torsion tes ts may be repeated several times on the same fiber.…”

Section: Bending and Torsional Propertiesmentioning

confidence: 99%

“…Ever since Speakman [5] provided the first comprehensive interpretation of the stress-strain behavior of keratin fibers, the measurements of tensile properties have been at the forefront of hair evaluation techniques. The Siffiplicityofthe measurement combined with the wealth of information it conveys, contributed greatly to its utilization and success.…”

Section: Tensile Propertiesmentioning

confidence: 99%

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Methods for Claim Support in Cosmetology: Hair Cosmetics

Wolfram¹

1999

Cosmetics

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“…The fiber is said to be in the yield region. This type of extension proceeds to about 30% strain for an a-keratin fiber in water and somewhat less for fibers in a drier environment [6]. At the end of the yield region, about 0.3 of the a-helical structure has been converted to the extended 0-keratin [3].…”

Section: Introductionmentioning

confidence: 99%

Dynamic mechanical properties of α-keratin fibers during extension

Danilatos

Feughelman

1979

Journal of Macromolecular Science, Part B

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Lincoln wool fibers have been tested for their dynamic modulus E' and loss angle 6 at various values of strain in the "Hookean", yield, and postyield regions by applying various rates of extension, and in atmospheres varying from 0 to 100% relative humidity. An estimate of the energy loss per cycle for the whole fiber exhibits only minor change over the complete range of change of the humidity and strain. The dynamic modulus E' and loss angle 6 change considerably with overall strain of the fiber, especially under more moist conditions. The variation of E' and 6 can be interpreted in terms of the microfibrilmatrix composite which forms the major component of a-keratin fibers. In particular, the mechanical effect of the unfolding of the a-helical structure contained within the microfibrils is shown to he independent of relative humidity. The results indicate that the a-helical component is responsible for a fiied amount of the Young's modulus of the initial stiff region (the Hookean region) of the stress-strain curve of Lincoln wool fibers. This fixed amount of 1.2 X lo9 Newtons mz is confirmed from other independent mechanical estimates.

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38—the Intracellular Structure of the Wool Fibre

Cited by 93 publications

References 6 publications

Natural protein fibers

Natural protein fibers

Methods for Claim Support in Cosmetology: Hair Cosmetics

Dynamic mechanical properties of α-keratin fibers during extension

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