Dynamic mechanical properties of α-keratin fibers during extension

Danilatos, G. D.; Feughelman, M.

doi:10.1080/00222347908215183

Cited by 21 publications

(10 citation statements)

References 16 publications

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“…The relaxation of the wool fiber in water is different in nature from the relaxation in the alcohols or at lower relative humidities [14,16], as was shown by Danilatos [19] in dynamic mechanical experiments on wool fibers in water. Danilatos observed that even at high frequencies, equivalent to short relaxation times, no upper plateau value for the modulus is reached and that the part of the relaxation curve experimentally accessible spans considerably more than the expected nine decades of time.…”

Section: Discussionmentioning

confidence: 93%

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The viscoelastic properties of wool and the influence of some specific plasticizers

Wortmann¹

1987

Colloid & Polymer Sci

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Abstract:The relaxation behaviour of Lincoln wool fibres in water and in three short chain aliphatic alcohols was measured. Applying a two phase model including a relaxation function based on a log-normal distribution of relaxation times a good systematic description of the data was found. The application of the model to the relaxation curves of wool fibers in the alcoholic media showed the invariance of the shape of the relaxation function, its shift on the log-time scale and the change of the elastical properties of the morphological components of the wool fibre depending on the aliphatic chain length of the alcohols. The importance of the apolar interactions for the elastic and viscoelastic properties of the morphological phases in the wool fibre is discussed.

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Section: Discussionmentioning

confidence: 93%

“…Various investigations have shown the applicability of the log-normal distribution in its integral form [2,15,16,19] to describe the relaxation function under various environmental and experimental conditions, yielding for the ln-time scale:…”

Section: Discussionmentioning

confidence: 99%

The viscoelastic properties of wool and the influence of some specific plasticizers

Wortmann¹

1987

Colloid & Polymer Sci

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“…Because of this consideratiun, the theoretical stiffness of the a-helix can be doubled. Druhala [11] ] used an effective cross-sectional area of the a-helix calculated from the known crosssectional area of the microfibril and arrived at a figure of about 2 nm2, but an average cross-sectional area of about 1 nM2 for the a-helix is preferable [23]. Consequently the theoretical value for the modulus of the a-helix can be further doubled.…”

Section: Consequentlymentioning

confidence: 99%

Anisotropy of Wool

Jong

Curiskis²

1985

Textile Research Journal

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The quantitative relationship is examined between torsion and tensile experiments done on wool fibers at various conditions of humidity and temperature. The relationship between torsion and tension measurements on a two component fiber depends on the volume fraction of the two mechanically distinct components. The two mechanical phases of the wool fiber are first assumed to be isotropic, but no assumption is made about their volume fraction. On this basis a mechanically elastic phase refers to approximately 5% of the fiber, not about 50% as is sometimes supposed. The remaining 95% of the fiber acts mechanically as a water penetrable viscoelastic matrix.Allowance for anistropy in the mechanically elastic phase does not significantly affect its volume fraction. If the viscoelastic matrix phase is regarded as constituting 95% of the fiber, it can be considered as mechanically isotropic at all water contents. Because of the low filament volume fraction obtained, the results suggest that the microfibril is not the mechanical unit corresponding to the water unaffected phase of the two phase model.The tensile Young's modulus E of dry and of wet wool is approximately 6.3 GPa and 1.75 GPa, respectively [ 18], whereas the torsional modulus G of wool is about 1.75 GPa when dry and, on average, 0.14 GPa when wet f 1, 281. These moduli are based on the actual cross-sectional area of the fiber at the conditions of measurement, .not on the wet cross-sectional area of the fiber -the latter being the way the moduli are sometimes quoted in the wool literature (e.g., references 3, 18, 23). This implies that the ratio of E/G for dry wool is 3.6, and that for wet wool the ratio is about E/G = 130. The value of the ratio E/G for an isotropic incompressible solid is 3. For a compressible isotropic solid, the ratio is less (see for example reference 3). Consequently wool is highly anisotropic when wet but also somewhat anisotropic when dry.The simplest way of accounting for this anisotropic behavior is to assume that the wool fiber consists of two phases [ 15], aligned parallel to the fiber axis. One of the phases has been thought to represent the microfibrils in the wool fiber. observable by electron microscopy [8,15,20,23], and their volume fraction can be calculated by chemical means and from X-ray data.The two mechanical phases we refer to in this paper are described by the terms &dquo;filament&dquo; and &dquo;matrix&dquo; in accordance with the terminology in the composite literature [29]. They represent mechanical components in the fiber and are not necessarily equivalent to the hitherto accepted notions of the microfibril and matrix in the wool literature [3,23].-, By making certain assumptions, outlined below, only tension and torsion measurements on wool fibers are required to determine the composition of wool in terms of its mechanical phases. We found that this composition does not correspond to the known volume fraction of the microfibrils in wool. The analysis and the measurements are confined to the low strain region (less...

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“…In order to compare the dynamic measurements with those obtained by relaxation techniques, the transformation of frequency to time was obtained using the method of Ninomiya and Ferry12: components of the complex modulus with magnitude E a t time t. In practice it was found that E ( t ) N E'(~)l,=i/t (2) Using the relation ( 2 ) , Mason's result is shown in Figure 1 together with those of Chaikin and Chamberlain for three relative humidities. Comparing these points, it seems that there must be an abrupt decrease of modulus from the value a t 100 kHz and 65% RH to the value at 20 kHz and 100% RH.…”

Section: The Tensile Modulus Of Keratin Fibers As a Function Of Timementioning

confidence: 99%

The time–temperature dependence of the complex modulus of keratin fibers

Danilatos

Postle

1983

J of Applied Polymer Sci

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SynopsisThe dynamic modulus and loss angle of wet keratin fibers have been measured a t frequencies between 6 and 1500 Hz in the temperature range 0.2-45°C. Some further measurements were performed a t different relative humidities. These results have been compared with other known results, and the agreement or discrepancies found are discussed. A theoretical curve fit has been introduced for a selected set of experimental results.

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Dynamic mechanical properties of α-keratin fibers during extension

Cited by 21 publications

References 16 publications

The viscoelastic properties of wool and the influence of some specific plasticizers

The viscoelastic properties of wool and the influence of some specific plasticizers

Anisotropy of Wool

The time–temperature dependence of the complex modulus of keratin fibers

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