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- Title
The Matrix Revisited.
- Authors
BREAKSPEAR, S.; EVANS, TREFOR; NOECKER, B.; POPESCU, C.
- Abstract
Feughelman’s two-phase model for keratin fibers provides a means for conceptualizing the properties and roles of differing protein structures within hair. Specifically, the crystalline α-helical keratin proteins that constitute the intermediate filaments/microfibrils are impenetrable to water, whereas the amorphous keratin within the surrounding matrix/keratin-associated protein is readily infiltrated. The presence of water solvates electrostatic bonding and progressively diminishes the contribution of the matrix protein through plasticization. In short, the wet-state mechanical properties of the fiber become dependent solely on the microfibrils, whereas in the dry state, the matrix also contributes to the structural integrity. In the hair care industry, there is a much higher tendency to perform hair testing in the wet state (e.g., wet-state instrumental combing, wet tensile testing, and even wet-state differential scanning calorimetry); however, such measurements contain no information about the amorphous matrix. Tensile experiments performed in the dry state show that the Young’s modulus can be two to three times higher than in the wet state, so clearly, the matrix can have a sizable contribution to fiber properties. The negative effects of various chemical treatments are well documented in wet-state tensile experiments, but dry-state testing can present anomalies. In particular, it is common to see the dry-state modulus increase after such treatments. It is worth emphasizing that this overall rise in modulus occurs even though the microfibril contribution is diminished. This suggests an enhanced matrix contribution that, in some cases, can be very sizable. This article presents a review of the literature focusing on how the matrix structure is described, in an effort to understand the contribution of the matrix to fiber properties. These ideas are supplemented with the authors’ experimental data to illustrate pertinent points and highlight some nontraditional outcomes and ideas.
- Subjects
EXTRACELLULAR matrix proteins; CYTOPLASMIC filaments; YOUNG'S modulus; DIFFERENTIAL scanning calorimetry; HAIR care &; hygiene; HAIR conditioners; INTEGRITY
- Publication
Journal of Cosmetic Science, 2021, Vol 72, p670
- ISSN
1525-7886
- Publication type
Article