Investigation of the film formation mechanism of oil-in-water (O/W) emulsions
Investigation of the film formation mechanism of oil-in-water (O/W) emulsions
复制标题
水包油（O/W）乳液成膜机理的研究
DOI：
10.1039/c0sm01561j
复制
发表时间：
2011-01-01
期刊：
影响因子：
3.4
通讯作者：
Luo, Jianbin
中科院分区：
文献类型：
--
作者：
Ma, Liran;Zhang, Chenhui;Luo, Jianbin
为了揭示水包油(O/W)乳状液的成膜机理，用相对光学干涉强度(ROII)法测量了非离子表面活性剂Tween80和Span 80稳定的水包油乳状液在两个固体表面之间的纳米膜厚度。研究发现，这种薄膜的厚度对轧制速度很敏感。与单相润滑油不同的是，在新材料供应充足的情况下，作为弹性流体动力学膜的单相润滑油的厚度总是随着速度的增加而增加，而水包油乳状液的成膜通常具有山丘状的外观(随着轧制速度的增加，厚度明显增加后，油膜在临界速度下经历崩塌到相对较低的厚度)。为了深入了解水包油乳状液的成膜机理，重点研究了不同乳化剂和不同含油量的O/W乳状液的临界成膜速度。可以观察到液滴在低速接触前聚集和破裂，从而形成油池。在滚压过程中，油池似乎起到了提供接触润滑剂的作用。用再乳化效应解释了速度超过临界值时油膜厚度崩塌的原因。提出了一个描述再乳化效果的理论模型，该模型建立了临界速度与油或乳化剂浓度之间的关系。
To reveal the film formation mechanism of oil-in-water (O/W) emulsions, the thicknesses of nanofilms of an aqueous paraffin oil emulsion, stabilized with the nonionic Tween 80 and Span 80 surfactants, were measured in confinement between two solid surfaces, by the use of the relative optical interference intensity (ROII) approach. Such films’ thicknesses were found to be sensitive to the rolling speed. In contrast to a single-phase oil lubricant, which as an elastohydrodynamic film had a thickness that always increased with speed when there was a sufficient supply of new material, the film formation of oil-in-water emulsions normally has a hill-like appearance (the film undergoes a collapse to a relatively low thickness at a critical speed after the evident rise in thickness with increasing rolling speed). The critical speeds for film formation of O/W emulsions with various emulsifiers and oil concentrations were focused on to gain an insight into the film formation mechanism of oil-in-water emulsions. Droplets can be observed to concentrate and break up before the contact at a low speed, which induces an oily pool. The oily pool seemed to act as the provider of the lubrication of the contact during the rolling process. The re-emulsification effect was employed to explain the collapse of the film thickness as the speed exceeded the critical value. A theoretical model was proposed to describe the re-emulsification effect, which established a relationship between the critical speed and the concentrations of either the oil or the emulsifiers.