Tribological Properties between Taut Hair Fibers in Wet Conditions: A New Shampoo Formulation for Eliminating Stick‐Slip Friction

Abstract

The tribological properties between taut hair fibers in wet conditions were investigated to evaluate the tangling/detangling performance of shampoo formulations during washing (particularly rinsing). A new setup for friction measurements between taut hair fibers was established. Using the setup, tribological properties of hair fibers treated with two shampoo formulations, whose tangling performances were different, were investigated. The base formulation for the shampoos was the same; the only difference was the type of amino-modified silicones used as conditioning agents. Shampoo (Sp) A (poor detangling performance) incudes water-insoluble silicone, and Sp B (excellent detangling performance) includes water-soluble silicone. The tribological behaviors between taut hair fibers treated with the diluted solutions of the Sp were very different; the Sp A-treated hair exhibited stick-slip sliding, whereas the Sp B-treated hair exhibited smooth sliding. This difference presumably comes from the different coacervation behaviors in the diluted solutions and resulting structure of conditioning film formed on hair surfaces. The smooth sliding (ideal for detangling) of Sp B-treated hair comes from the two-layer structure of the conditioning film on hair; positively charged amino-modified silicone dissolved in water adsorbed immediately on negatively charged hair surface, followed by the physical adsorption of coacervates on the adsorbed silicone layer. The outer coacervate layer is easily removed during sliding, and smooth sliding comes from the low friction of the silicone layer. The relationship between the type of amino-modified silicones, conditioning film formation on the surface, and tribological properties was discussed, which gives insights into designing Sp formulations with excellent detangling performance.

Nanoscale friction of biomimetic hair surfaces

“…Stick-slip friction was also observed in previous experiments using wet bleached hair-hair contacts. 30 The highest CoFs in Fig. 7(a) are obtained for the ultimately bleached system across all sliding velocities.…”

“…2–7 Consequently, the kinetic friction of hair has been studied using a wide range of experimental techniques from the macroscale to the nanoscale. 8–30 The friction between nanoscale tips and single hairs, 10–14,18,22,26 as well as crossed hair–hair contacts, 23–25 have been investigated using atomic force microscopy (AFM) and high-load nanotribometers. 27 Understanding the friction between hairs is crucial since this dominates the overall resistance felt during combing and brushing.…”

Nanoscale Friction of Biomimetic Hair Surfaces

“…This observation is consistent with previous experiments using wet bleached hair-hair contacts. 30 The highest CoFs are obtained for the fully damaged system across all sliding velocities. In this case, both surfaces are fully separated by a water film with a thickness of ≈2.6 nm and stick-slip is promoted by surface-bound hydration layers on the highly hydrophilic surfaces.…”

“…2–7 Consequently, the kinetic friction of hair has been studied using a wide range of experimental techniques from the macroscale to the nanoscale. 8–30 The friction between nanoscale tips and single hairs, 10–14,18,22,26 as well as crossed hair-hair contacts, 23–25 have been investigated using atomic force microscopy (AFM) and high-load nanotribometers. 27 Understanding the friction between hairs is crucial since this dominates the overall resistance felt during combing and brushing.…”

Friction dynamics of human hair treated with water or cationic surfactant aqueous solution

“…In the case of AFM, it was possible to measure the surface roughness, adhesion, and friction properties of the hair (Karuppiah et al, 2009; LaTorre & Bhushan, 2005; Smith et al, 2013). When friction was measured between two hair fibers in dry and wet conditions, completely different sliding behaviors were observed (Miyamoto et al, 2021). In air and water, smooth and stick–slip sliding was observed.…”