Effects of age on the structure and bleaching/dyeing behaviour of hair

Abstract

The structure and bleaching/dyeing behaviour of hair sampled from people of various ages were investigated to provide guidance for wig-making. Hair surface and cross-sectional morphology were investigated by scanning electron microscopy, whereas the number density and size of melanin granules were evaluated by transmission electron microscopy. The suitability of hair for dyeing was determined by the trade-off between the fracture strength and lightness of bleached samples. Hair collected from 26-year-olds showed the highest number density and the lowest size of melanin granules, thus featuring the lowest mechanical strength reduction and the highest lightness increase after bleaching. The optimal bleaching conditions for such hair were identified as bleaching time = 80 minutes, hydrogen peroxide (H 2 O 2 ) concentration = 60 mL/L, and bleaching temperature = 75°C. Considering its resilience to damage and favourable dyeing behaviour, hair sampled from 26-year-olds was concluded to be most suitable for wig-making. Thus, the present research provides guidance for the selection of raw materials for wig-making.

A three-dimensional arched solar evaporator based on hydrophilic photothermal fibers inspired by hair for eliminating salt accumulation with desalination application

“…1a-i). 52,65 Melanin particles with a micro–nano structure have a significant specific surface area, allowing them to possess high absorption in the UV-Vis-NIR region (250–2500 nm) (Fig. 1b).…”

“…In particular, hair with black colour (black hair) have many photothermal melanin particles dispersed uniformly in the cortex, and the cuticle covers the surface of the hair with fish or tile structures to trap heat, which is made up of a lipid layer and 7–10 layers of flat hair cuticle cells to possess low density, low thermal conductivity and hydrophilicity. 51,52 Therefore, black hair can absorb solar energy and convert it to heat without the need for further processing, and the fluid will rise through the interstice between the black hair by the Marangoni convection and capillary effects, which are common phenomenona in nature because of the existence of a tension gradient in the interfaces. 53–56…”

“…In particular, hair with black colour (black hair) have many photothermal melanin particles dispersed uniformly in the cortex, and the cuticle covers the surface of the hair with sh or tile structures to trap heat, which is made up of a lipid layer and 7-10 layers of at hair cuticle cells to possess low density, low thermal conductivity and hydrophilicity. 51,52 Therefore, black hair can absorb solar energy and convert it to heat without the need for further processing, and the uid will rise through the interstice between the black hair by the Marangoni convection and capillary effects, which are common phenomenona in nature because of the existence of a tension gradient in the interfaces. [53][54][55][56] Inspired by the structure of black hair, we report a strategy to construct an efficient three-dimensional arched solar evaporation model with hydrophilic photothermal bers, in which the Marangoni convection and capillary effects are generated by local contact between the photothermal material and water, triggering continual water ow and maintaining the devices with continuous water supply (Scheme 1).…”