Water-based Lubrication for Eliminating Hair Tangling in Wet Conditions

Abstract

The tribological properties between single hair fibers in wet conditions were investigated to evaluate the tangling/detangling performance of shampoo formulations during washing. A new setup for friction measurements between taut single hair fibers under large load was established. Using the setup, friction of hair fibers treated with different cosmetics solutions were evaluated; particular attention was focused on the static (stick-slip) friction behavior which determined the tangling/detangling performance. We found that a water-soluble silicone-type lubricant, bis-isobutyl polyethylene glycol (PEG)-14/amodimethicone copolymer (BIPA), in dilute aqueous solution eliminated stick-slip behavior; the shampoo formulation including BIPA exhibited excellent detangling performance. The detailed mechanism of why BIPA exhibited such excellent lubricity was further investigated by the precise nanotribological measurement using the surface forces apparatus. BIPA aqueous solution was confined between molecularly smooth mica surfaces, compressed under load, and sheared between each other. The obtained friction coefficient was extremely small, of the order of 10^–5, indicative of the “hydration lubrication” mechanism. BIPA has positive charges in aqueous solution which forms adsorbed film on negatively charged mica surface (hair surface is also negatively charged). The BIPA film has hydrated water layer on the top surface which has high fluidity and contributes to excellent lubricity.

graphical abstract