Stabilisation of water-in-oil emulsions to improve the emollient properties of lipstick

Taylor, Mark Stewart (2011). Stabilisation of water-in-oil emulsions to improve the emollient properties of lipstick. University of Birmingham. M.Res.

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Abstract

The stabilisation of water-in-oil (W/O) emulsion lipstick with up to 40% aqueous phase has been investigated. The intention is to use these emulsions to deliver moisture, active hydrophilic ingredients and humectants to the lips. Three lipophilic non-ionic emulsifiers were used to stabilise the water droplets, PGPR (HLB 1.5 ± 0.5), Span 80 (HLB 4.3) and a blend of Span 80 with Tween 80 (HLB 5). These were investigated with or without crystalline particles of microcrystalline and carnauba wax. Emulsification was carried out using high shear (high energy/ short time via a Silverson L4 RT High shear laboratory mixer). The emulsions were produced at 95 to 100 °C to ensure that no crystals were present during droplet formation. This was then followed by rapid cooling to -20 °C over a period of 20 minutes using refrigeration. Emulsion stability and droplet size distribution were determined using pNMR in conjunction with optical microscopy and cryo-SEM. A comparison of the physical and viscoelastic properties of the emulsion lipstick formulations was made with a conventional lipstick. Penetrometer, compression and rheological non-destructive oscillation testing were used for this comparison. Emulsions prepared with PGPR were shown to be more stable and had smaller droplet sizes and droplet size distributions than those prepared with Span 80 and the blend of Span 80 with Tween 80. As the water content increased the ‘lipsticks’ softened and became less elastic. This trend could be removed using additional crystalline solids in the continuous phase.

Type of Work:

Thesis (Masters by Research > M.Res.)

Award Type:

Masters by Research > M.Res.

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