Centre for Formulation Engineering, School of Chemical Engineering, University of Birmingham, Birmingham, B15 2TT, UK.
Int J Cosmet Sci. 2013 Dec;35(6):613-21. doi: 10.1111/ics.12085. Epub 2013 Aug 26.
Water-in-oil emulsions in lipsticks could have the potential to improve moisturizing properties and deliver hydrophilic molecules to the lips. The aims of this work were (i) to investigate the effect of emulsifier type (polymer vs. monomer, and saturated vs. unsaturated chain) and concentration on droplet size and (ii) to investigate the effect of wax ratio (carnauba wax, microcrystalline wax, paraffin wax and performalene) and aqueous phase volume on material properties (Young's modulus, point of fracture, elastic modulus and viscous modulus).
Emulsion formation was achieved using a high shear mixer.
Results showed that the saturated nature of the emulsifier had very little effect on droplet size, neither did the use of an emulsifier with a larger head group (droplet size 18-25 μm). Polyglycerol polyricinoleate (PGPR) resulted in emulsions with the smallest droplets (3-5 μm), as expected from previous studies that show that it produces a thick elastic interface. The results also showed that both Young's modulus and point of fracture increase with increasing percentage of carnauba wax (following a power law dependency of 3), but decrease with increasing percentage of microcrystalline wax, suggesting that the carnauba wax is included in the overall wax network formed by the saturated components, whereas the microcrystalline wax forms irregular crystals that disrupt the overall wax crystal network. Young's modulus, elastic modulus and viscous modulus all decrease with increasing aqueous phase volume in the emulsions, although the slope of the decrease in elastic and viscous moduli is dependent on the addition of solid wax, as a result of strengthening the network.
This work suggests the potential use for emulsions in lipstick applications, particularly when PGPR is used as an emulsifier, and with the addition of solid wax, as it increases network strength.
口红中的油包水乳液有可能改善保湿性能，并将亲水性分子递送到嘴唇上。本工作的目的是：（i）研究乳化剂类型（聚合物与单体，饱和与不饱和链）和浓度对粒径的影响；（ii）研究蜡比（巴西棕榈蜡、微晶蜡、石蜡和蜂蜡）和水相体积对材料性能（杨氏模量、断裂点、弹性模量和粘性模量）的影响。
乳液的形成是使用高剪切混合器来实现的。
结果表明，乳化剂的饱和性质对粒径几乎没有影响，使用具有较大头部基团的乳化剂也没有影响（粒径约 18-25μm）。正如先前的研究表明，聚甘油蓖麻醇酸酯（PGPR）可产生最小的乳液液滴（~3-5μm），这是意料之中的，因为它可产生厚的弹性界面。结果还表明，随着巴西棕榈蜡百分比的增加，杨氏模量和断裂点都增加（遵循 3 的幂律依赖性），但随着微晶蜡百分比的增加而减小，这表明巴西棕榈蜡包含在由饱和成分形成的整体蜡网络中，而微晶蜡形成不规则的晶体，破坏了整体蜡晶体网络。杨氏模量、弹性模量和粘性模量都随乳液中水相体积的增加而降低，尽管弹性和粘性模量的降低斜率取决于固体蜡的添加，因为这增强了网络。
本工作表明，乳液在口红应用中具有潜在的用途，特别是当 PGPR 用作乳化剂时，并且添加固体蜡时，因为它增加了网络强度。
