The evolving mechanical response of curly hair fibres subject to fatigue testing

Ngoepe, Malebogo; Cloete, Elsabe; Berg, Claire van den; Khumalo, Nonhlanhla P.

doi:10.1016/j.jmbbm.2021.104394

Cited by 4 publications

(1 citation statement)

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“…Direct comparisons of the mechanical properties of different hair types under the same conditions are scarce in the literature; however, it is generally agreed that Asian and Caucasian hair have higher tensile strength than African hair; thus, the tensile strength appears to decrease with increasing curliness [7,16,61,62]. Recent studies have suggested the existence of a toe region at the start of the stress/strain curve of very curly hair, thus proposing that it exhibits a certain amount of tensile resistance that is not reflected in the stress/strain plot of straight hair [63,64]. Some studies have also reported different fibre breakage patterns for different hair types subjected to tensile stress, but such data need further corroboration [49,65].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

How different is human hair? A critical appraisal of the reported differences in global hair fibre characteristics and properties towards defining a more relevant framework for hair type classification

Daniels¹,

Fraser²,

Westgate³

2022

Intern J of Cosmetic Sci

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This review critically appraises the reported differences in human hair fibre within three related domains of research: hair classification approaches, fibre characteristics and properties. The most common hair classification approach is based on geo-racial origin, defining three main groups: African, Asian and Caucasian hair. This classification does not account sufficiently for the worldwide hair diversity and intergroups variability in curl, shape, size and colour. A global classification into eight curl types has been proposed but may be too complex for reproducibility. Beyond that, hair cross-sectional shape and area have been found to have an inverse relation to curl: straighter fibres are circular with larger cross-sectional area, whilst the curlier fibres are elliptical with smaller cross-sectional area. These geometrical differences have been associated with bilateral vs homogenous distribution of cortical cell in curly vs straight hair respectively. However, there is no sufficient data demonstrating significant differences in hair amino composition, but proteomic studies are reporting associations of some proteins with curly hair. Eumelanin's relative abundance has been reported in all hair colours except for red hair which has a high pheomelanin content. Higher tensile and fatigue strength of straight hair are reported, however, curly hair fragility is attributed to knotting, and crack and flow formations rather than the structural variations.African hair has been found to have the highest level of lipids, whilst the water sorption of Caucasian hair is the highest, and that of Asian hair the lowest. Not all comparative studies clearly report their hair sampling approaches. Therefore, to strengthen the robustness of comparative studies and to facilitate cross-study data comparisons, it is recommended that the following hair defining characteristics are reported in studies: hair cross sectional diameter/area, curl type, hair assembly colour, as well as where possible donor data (age/gender) and sample pooling approach. AbstraitCette revue évalue de façon critique les différences rapportées sur les fibres capillaires humaines dans trois domaines de recherche connexes : les approches

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