Stiffness of Human Hair Correlates with the Fractions of Cortical Cell Types

Improving the physicomechanical performance of geopolymer mortars using human hair as fibers: new horizons for sustainable applications

Blast furnace slag-based geopolymer mortars strengthened with human hair fibers were synthesized in the present study. The mixture of NaOH and Na₂SiO₃ was used as activating solution. Zero percent, 0.25%, 0.5%, 0.75%, 1%, and 1.25% hair fibers were added by weight of slag. Several analytical approaches, including compressive strength, flexural strength, P-wave velocity, bulk density, porosity, water absorption, infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, were used to assess the physicomechanical and microstructural characteristics of the geopolymer mortars. Overall, the results found revealed that the incorporation of human hair fibers into the slag-based geopolymer matrix brought about a noticeable improvement in the mechanical characteristics of the geopolymer mortars. Similarly, based on FTIR analysis, the geopolymer mortar is characterized by the presence of three principal bonds, namely, the stretching of Al-O, a shift of the absorption band of the Si-O-Si (Al), and the stretching of the O-C-O. Likewise, the mineralogical analysis shows that quartz and calcite are two crystalline phases dominant in the geopolymer matrix. In addition, SEM-EDS analysis shows a dense and continuous morphology devoid of microcracks with a few pores existing on the matrix surface with perfect integration of the hair fiber in the geopolymer matrix. According to these relevant properties, the synthesized geopolymers have potential applications as a suitable substitute for many Portland cement-based materials whose manufacture is energy-consuming and polluting.

Special Issue “Recent Advances in Hair Science and Hair Care Technologies”

Scalp hair is very important for men and women especially in terms of fashion and appearance [...]

The Secrets of Beautiful Hair: Why is it Flexible and Elastic?

Beautiful hair, so called “SHINAYAKA” hair in Japanese, has a good appearance not only when stationary but also when in motion, and it is a highly desirable hair condition for Japanese consumers. We investigated such SHINAYAKA hair, which was selected by sensory evaluation, for the relationship between physical properties, such as flexibility and elasticity, and hair structure. It has already been reported that human hair cortical cells have two types, similar to wool: the ortho-like cortex and the para-like cortex. Microscopic observation revealed that the ortho-like cortex is distributed in the outer layer of the hair (near the hair surface) and the para-like cortex exists in the inner layer (near the center of the fiber). This cell distribution, a concentric double-layered structure, was deemed to be a characteristic of SHINAYAKA hair. Furthermore, analysis of physical properties showed the difference between the elasticity of the outer layer and inner layer, and that this difference was bigger in SHINAYAKA hair compared to other hair. This phenomenon was observed not only in Japanese hair, but also in Caucasian hair. In addition, we have developed a new technology for creating “SHINAYAKA” hair by treatment with succinic acid. Inflexible and inelastic hair can be changed by this treatment, and its flexibility and elasticity improve by selective reduction of stiffness of the outer layer.