Particulate lubricants in cosmetic applications

Abstract

Polymer powders are commonly added to cosmetic formulations to improve product performance and skin feel. This study investigates the effect of particle concentration and size on the lubricating properties of powder suspensions. Results are reported for various particle sizes and concentrations.When the tribological contact was fully immersed the addition of particles had no effect.However different behaviour was observed when the contact was only partially-lubricated. In this case, a three stage friction coefficient curve was observed. By varying the particle size and concentration it was shown that the duration and magnitude of each stage can be controlled.

Cosmetic powder suspensions in compliant, fingerprintlike contacts

“…Unlike with tests using smooth disks, 7 there is no initial constant low friction region, referred to in previous work as stage 1. Only the two subsequent stages of behavior, seen using particulate suspensions with smooth disks, are observed with textured disks.…”

“…For a dry pure sliding contact, the value for l def is much lower than the total friction coefficient, 7 which shows the overwhelming importance of interfacial adhesion in dry contacts.…”

“…7 A steady increase in friction is then observed over the initial $400 s. This results from progressive starvation due to the loss of lubricant from the contact inlet reservoir. This loss may result from either capillary flow along the disk grooves away from the contact, or evaporation of the small test lubricant volume, or both.…”

“…7 In addition to water and cosmetic particles, each lubricant contained a rheology modifier (Carbopol 980; 0.1 wt. %) and an emulsifier (Polysorbate 20; 1 wt.…”

“…In a previous study, 7 particulate lubricants were investigated under conditions resembling a cosmetic application. An in vitro system was set up using a ball-on-disk tribometer with a compliant contact formed between a smooth polydimethylsiloxane (PDMS) ball and disk.…”