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- Title
Moisture in the Cuticle Sheath: Effects on Hair Mechanical and Cosmetic Properties.
- Authors
GAMEZ-GARCIA, MANUEL
- Abstract
The role of moisture in the cuticle sheath has not been properly explored so far. In this paper, analysis and experiments indicate that moisture variations in the cuticle sheath have a significant impact on its shear and tensile modulus and, therefore, on the overall hair mechanical and cosmetic properties. Analysis shows that if there is an imbalance in the required moisture content in the cuticle cell inter- and intralayers, steep layer moduli mismatches and stress concentrations are generated across interfaces. Imbalances of this type often arise when the hair has very low levels of moisture or when it is transiently subjected to high temperatures, becoming more severe with tensile extensions. For instance, at high elongations and near the yield point, the intermediate filaments in the cortex undergo an alpha to beta transformation. This keratin phase transition occurs at both low- and high-moisture conditions and causes the cortex tensile modulus to decrease, allowing for higher deformations without severe stress buildup. In contrast, at high elongations, the cuticle sheath has no such stress dissipation mechanism, and high-stress concentrations appear across the cuticle cells. Therefore, moisture loss in the cuticle cells accompanied by extensions aggravate stress concentrations resulting in damage at the cuticle cell cement boundaries.
- Subjects
CUTICLE; MOISTURE; STRESS concentration; CYTOPLASMIC filaments; HAIR; HAIR conditioners
- Publication
Journal of Cosmetic Science, 2021, Vol 72, p687
- ISSN
1525-7886
- Publication type
Article