A Transition Temperature in Wool Fibers Under Stress in Relation to Structure

Weigmann, H.-D.; Rebenfeld, Ludwig; Dansizer, C. J.

doi:10.1177/004051756503500704

Cited by 17 publications

(9 citation statements)

References 24 publications

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“…On peut cependant admettre que: -au niveau de la zone ilastique, l'ilasticitd augmente en fonction de la ternpirature, ce ph6nomene est accompagni d'une diminution de la contrainte au point A (17); -l'allongement dans la 'post yield' region est constant jusqu'i une temperature caractiristique puis il augmente rapidernent quand cette temperature est dCpassCe. On ditermine une tempdrature de transition i 85,S"C (16,18).…”

Section: Influence De La Temperature (161718)unclassified

Influence des variations thermiques sur les propriétés mécaniques du cheveu

Bories¹,

Martini²,

Et³

et al. 1984

Intern J of Cosmetic Sci

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Synopsis A previous study having shown that there was no modification in superficial or deeper hair structure at temperatures below 100 degrees C, the influence of hair-drying conditions on mechanical properties has been examined. The hair speed and hair temperature given by different types of hair-drying equipment were considered and a novel method used each hair as its own control. Stress/strain curves were followed using an electrodynamometer and a range of hair types was considered: normal, grey, denatured, and bleached, the definitions being given by both appearance and the stress/strain curve. In comparison with ultimate structure, mechanical properties were modified at a lower temperature. The stiffness of the hair starts to increase markedly already at 40 degrees C for a drying time of 2 to 3 minutes and this appears.

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Section: Influence De La Temperature (161718)unclassified

Influence des variations thermiques sur les propriétés mécaniques du cheveu

Bories¹,

Martini²,

Et³

et al. 1984

Intern J of Cosmetic Sci

View full text Add to dashboard Cite

show abstract

“…Furthermore, the post-yield region modulus is lower for reduced fibers and further reduces with temperature to virtually disappear at 100°C [ 29,33 ] . Crewther also found the virtual removal of the post-yield region by reduction and its restoration on removing the SHgroups from the disulfide interchange by methylation [ 7 ] .…”

mentioning

confidence: 99%

“…Weigmann et al [33] determined the influence of temperature and SH-content on the turn-over point between yield and post-yield regions for Buenos Aires wool fibers. For untreated fibers, the turn-over point shifts to higher strains above a transition temperature of around 70°C.…”

mentioning

confidence: 99%

The Stress/Strain Curve of α-Keratin Fibers and the Structure of the Intermediate Filament

Wortmann

Zahn

1994

Textile Research Journal

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Staying in the tradition of Astbury's hypothesis about the role of the α ⇔ β transformation for the stress/ strain-curve of wool fibers and of Feughelman's X/Y-zones model, the interrelation between the morphological structure of keratin fibers and the shape of their stress/strain-curve in water is reevaluated. The yield and post-yield regions can be attributed to the opening up of two distinctly different and well defined portions of the monomer of the intermediate filament; the increased slope in the postyield region can be attributed to the influence of the sulfur bonds in one of the segments.The role of the sulfhydryl-disulfide interchange reaction for the appearance of the post-yield region is pointed out and the molecular mechanisms for achieving the maximum possible strain are discussed.J. B. Speakman was the first prominent protagonist of the theory that the mechanical properties of wool fibers have an important influence on their processing performance. In consequence, he placed a major emphasis on measuring stress/strain-curves and their changes with physical and chemical modifications [ 29 ] . The upper curve in Figure 1 shows somewhat schematically the stress/strain curve of a wool fiber in water. FIGURE 1. Stress/strain curve of a wool fiber in water (schematically ) and the components of the two-phase model. Stress and strain are not drawn to scale. _ On the molecular level, structural investigations using x-ray diffraction led to the discovery of axially oriented a-helices by Pauling and Corey and of the ahelix b 0-pleated sheet transformation with strain by Astbury and Woods. Studies by transmission electron microscopy revealed the existence of lightly stained cylindrical structures, traditionally referred to as &dquo;microfibrils,&dquo; embedded in a more darkly stained &dquo;matrix&dquo; phase [ 16 ] .On the basis of knowledge of the microscopic and molecular morphology of a-keratin fibers, major attempts have been made, especially by Hearie et al. [ 21,22 ] and Feughelman [ 15 ] , to consistently interpret the shape of the stress/strain-curve in relation to fiber structure. Both these approaches are based on the twophase model proposed by Feughelman [ 10 ] , where the filament phase dominates the stress/strain curve in the wet state, while the amorphous matrix phase either plays a minor role [ 15 or exhibits a significant contribution only at high strains [ 21,22 ] .Si nce these versions of the structure / property relationships [ 15,22 ] , more detailed information has become available on the structure of the &dquo;microfibrils,&dquo; in modern semantics referred to as &dquo;intermediate filaments.&dquo; This has enabled us, when expanding a previous account of our research [ 39 ]. to reevaluate the models on a molecular level. The model refinement, which stays in the tradition of Feughelman's X/Yzones model [ 1 l ,15 ] , achieves an improved consistency of the property / structure relationship. Structural Principles and Stress/Strain Properties of Fibrous Keratins a-Keratin f...

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“…It is interesting to note that this temperature roughly agrees with a transition temperature found in wool fibers in water through mechanical tests by Feughelman et al (60 -70°C), 26 which was later on related to sulphydryl-disulphide interchange by Weigmann et al (70°C). 27 With eq. (1), we have for the saturation regain, rg H , related to the Henry term,…”

Section: Henry Termmentioning

confidence: 99%