Emulsions Case Study

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1. INTRODUCTION

1.1 Scope
Emulsions, basically Oil in water (O/W) emulsions are of huge importance and they are the basis or the major building blocks of many skin care products available like sun care, moisturization, anti-aging etc. Emulsions are formed by mixing two immiscible liquids by applying an external force. Normally there are two types of emulsions i.e. oil-in- water emulsions (o/w) and water-in-oil emulsions. The liquid with higher amount is the continuous phase while the liquid with smaller amount or the liquid which disperses out in the continuous phase is the dispersed phase. In our case, water is the continuous phase while oil is the dispersed phase.
This thesis basically concentrates on the spreading behavior of (a) oils and (b) emulsions on model surfaces. The oils used were chosen from oils typically used in cosmetics, either as emollient or as a delivery vehicle. In this part of study, we focus on the wetting behavior of low energy substrate: Teflon, which has been used as a model substrate for spreading of oils. Our study targets on identifying various parameters like concentration, viscosity and interfacial tension values for their roles in spreading.

1.2 Motivation and Research Objective
For achieving ample efficacy and customer efficacy of the cosmetic emulsion, spreading is an important property. Upon application of these products on skin, water evaporates out leaving behind the oil phase. The amount of spreading that happens from the left over oil phase decides the adequate efficacy of these products. The spreading phenomenon is also investigated due to its widespread and great scientific applications. However, nowadays the number of studies on spreading performed in the cosmetic domain ...

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...and their molecules goes and stick to the bulk molecules; as a result of which the average droplet size of the emulsions shift to larger value.

1.4.4 Coalescence
When there is a disturbance to the liquid film between the two or more droplets, they try to fuse together forming a bigger droplet. This process is known as coalescence. This result because of the fluctuation in surface films due to which the droplets comes closer to each other and also due to the strong Vander Waal’s force of attraction between droplets.

1.4.5 Phase Inversion
Phase inversion is the process in which particular oil-in- water emulsion can be converted to a water-in-oil emulsion over time. This results due to different arrangement of surfactant molecules at the interface. Increasing temperature and concentration of surfactant are some of the factors that promote phase inversion.

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