Development of Emulsion Property

• Student’s name: Yang Jiang

1. Abstract

In recent years, emulsion has taken an important port in our life, such as cosmetic and some other cosmetic industries. The property of the emulsion has a direct impact on our daily life. This paper chose the process of produce bath gel to provide what makes the property change, how to control it and how to make it better. In technically, chose different viscosity, speed rate and concentrate to get different product. Aim to find the best one.

2. Introduction

An emulsion is formed when two more insoluble phases are blended together with one of them is in the form of liquid drop. Emulsions belong to a two-phase system ofmatter which is calledcolloids. The emulsion is generally non-transparent and inherently unstable. The diameter of drop is between 100nm to 10mm, and the size of it could be observed by an optical microscope. However in this work, an emulsion consisting of two liquids is the objective many companies and institutions tend to take advantages of. To sum up, two types of this emulsion can be formed by mixture. The one which shapes into a water-in-oil system is called W/O emulsion and another is oil-in-water system which is called O/W emulsion.

Emulsion is widely used in manufacturing as a common form of formulated products, and whose properties have been studied in agriculture, medicine, cosmetics and food. Some kinds of emulsion are necessities in daily life, such as: milk, ice cream, vinaigrettes, rubber, latex, crude oil emulsions and even some cutting fluids formetal working. However, an emulsion cannot be obtained easily because emulsions cannot be formed spontaneously. Energy is needed to form an emulsion through shaking, stirring, homogenizing or exposure to power ultrasound. And in this proposal, the emulsion is formed by stirring. Some mixing devices will be adopted to blend Silicon oil and water together. So it is apparent that some parameters can be fixed as constant and the others are what we are interested in to investigate.

A number of the physicochemical properties of emulsions can only be understood with reference to their dynamic nature. Many properties depend on the volume fraction of both phases and the type of emulsifier present. Because of the low solubility of oil in water it is usually assumed that the oil in an emulsion droplet is isolated from that in neighboring droplets. Emulsion stability refers to as the ability of resisting change in its properties over time. Coalescence happens when droplets crash into each other and combine to form a larger droplet, so the mean droplet size increases over time. Emulsions can also undergocreaming, in which the droplets rise to the top of the emulsion.

In order to keep the emulsion stability, an appropriate surface active agent should be decided to add into the system to increase the kinetic stability of an emulsion so that the size of the droplets keep unchangeable significantly with time.

The emulsions produced by dispersion of a liquid into another insoluble liquid is an aspect of great benefits in cosmetic, pharmaceutical, chemical, and food industries. Present industrial methods applied in emulsification processes have been fully developed and studied. For example, rotor stator devices, and static mixers techniques are well-accepted as important ways of producing small droplets but with another side effects on the liquids, bringing potential hazards to the properties of compounds. It has been proved by plenty of researchers that droplet size is one factor of the most difficult ones to control because some instability phases will be produced among this during the controlling process.

Rotor-stator mixers are usually used for processing of disperse/break solid particles and aggregates and also to colloidal liquid-liquid systems. Such as cosmetic, food, pharmaceutical, health care products and many other industries. As the drop size affects the processing and the properties of the products in the emulsification. The mechanisms that break the drops is the key for design process. Rotor and stator are the two main mechanisms which can break drops in rotor-stator devices.

For emulsification, the industrial processing and some of the product properties are influenced by the drop size. In a two-phase process, the mass transfer rate is proportional to the interfacial area between the two phases. The drop size distribution is varied with the conditions inside the vessel and the length of mixing time and thus the interfacial area is changed with it. Hence successful processing steps are designed by establishing deep understanding of the mechanism of drop breakup. In general, two competing theories have been proved on drop breakup mechanisms to give a good explanation to this phenomenon. So one theory shows that droplet breakup is produced by turbulent eddies (energy dissipation rate) and another is due to the agitator shear rate.

Another widely used mixing device: static mixers, which are also called motionless mixers, have become standard equipment in the process industries. Their application in continuous processes is a good choice to traditional agitation because generally better performance can be obtained with this device at lower cost.

There are also some other kinds of mixing devices such as CSTR and batch reactor. But according to the cost, property of the emulsion, the conditions in the lab and many other factors I chose rotor-stator mixer as the agitator.

The working principle of rotor-stator mixture is shown as below in Figure 1.

Figure 1: Basic principle of rotor – stator mixture when running

In this essay, comparing different emulsion got from different conditions of the mixing due to different conditions of mixing have a direct result that the droplet size changed. The property of the emulsion is influenced by the droplet size.

The viscosity and storage modulus of W/O and O/W fine concentrated emulsions were increased by the reduction of droplet size. And the shear-thinning effects got stronger in the fine emulsions

As silicon oil is the resource which is manly used in cosmetics. How bath gel be different by the different size of droplet is the main purpose. As the rheology of emulsion is influenced by the droplet size, various of bath gel might be produced with different property.

3. Background

3.1Theory

3.2. Literature review

There have been a large amount of methods of producing polymer emulsions in industrial manufacturing. One of the mainly way of them is emulsion polymerization. Emulsion polymerization has large polymer relative molecular mass, fast reaction rate, low pollution and the equipment and technology with which to produce the emulsion products is easy to get and operated in generation. Recently, more and more scientists have focused on this area. Many factors have an important influence on both yield and quality of the polymerization product in the process of emulsion polymerization, such as the type and concentration of emulsifier, the sorts and concentration of initiator, the intensity of stirring, reaction temperature, the category and concentration of electrolyte and some other technological parameters.

Emulsion polymerization system is a multiphase system, the effect of stirring turn the monomer into droplet separately, which is good for heat transfer and mass transfer. And keep the system mixing, constant temperature, avoid from local overheating. The yield and quality of the emulsion polymer are controlled by stir directly. Many scholars carried out extensive research on the influence of the mixing of emulsion polymerization. Such as Shunmukhan et al, Omi et al, Nomura et al who had studied the effects of mixing on low solid content of the emulsion. Vanderhoff, M. Zubitor, S. Oprea et al, Matejicek et al who has studied the effects of mixing on high solid content emulsion polymerization (> 50%).This paper elaborated how the mixing effects on the quality of products.

1. Influence of the style of agitator on polymerization

The production capacity of reactor, the quality of product and the accident caused by cooling or heating are all related to the type of agitator. Shearing action, circulating mode and the mixed-ability which were generated by mixing are given by the specific style of agitator. And so does the state of macro-flow. 3 factors should be considered when selecting the style of agitator: 1. High heat transfer coefficient should be ensure from the reactor wall or Immersion coil to the reactants; 2. An obvious effect should be provided in the stirring; 3. Low consumption of energy in the stirring. Therefore, in the process of emulsion polymerization, especially for the industrialized production, we should find out the most appropriate style of agitator by strengthen the research about the relation between mixer and emulsion polymerization.

2. Influence of mixing intensity on the emulsion polymerization 2.1 The influence of mixing intensity on latex particle size

In the process of emulsion polymerization, mixing intensity has a direct impact on the latex particle size. With the revolution of mixing higher, monomer was divided into smaller beads, the surface area of monomer droplet was larger per cubic centimeter of water, the amount of emulgator adsorbed on the surface was increased, the numbers of micelle were reduced per cubic centimeter of water, the rate of nucleation decreased in phase 1, so does the emulsion grains generated, if the initial monomer amount is fixed, the particle size of latex increases. With the increase of stirring intensity, latex particle size also increases in the process of semi-continuous emulsion polymerization are analyzed and verified by M. Zubitur et al, S. Opera. And they further points out that the stirring intensity also affect the nucleation mechanism: under the low intensity, the micellar nucleation and monomer droplet nucleation were presented. And the distribution of particle size is unimodal features. Therefore, in the emulsion polymerization, the diameter of latex particle is related to the number of latex particle, with the increase of stirring intensity, the number of latex particle decreased, the diameter of latex particle increased, vice versa.

2.2 The influence of mixing intensity on the stability of emulsion

Emulsion stability is one of the most valuable properties in researches involving emulsions concerned by numerous scientists. The influence of stirring intensity on the emulsion stability is mainly manifested in polymerization stability. During the process of emulsion polymerization, droplet condensation may happen raised by coalescence of latex particles within the emulsion, as a result of the loss of polymer emulsion stability. In other cases, during the emulsion polymerization, the condensate may deposit on the reactor components which are accumulated in a thick layer. This is one kind of phenomenon of gel. These phenomena may make the color of emulsion fade away, delicate feeling disappear, affecting the quality of the product seriously.

Stability of high solid content emulsion has two important areas which should be concentrated on to investigate further. On one hand, with an increase in stirring intensity and collision frequency, the emulsion stability which plays an important role in manufacturing products will be decreased. On the other hand, due to the solid content increased inside the emulsion, and the high emulsion viscosity, the emulsion stability in the heat transfer process impact much on the quality of emulsion products. Especially when the mixing intensity is too high, the material internal shearing action is too frequent; the stability of the emulsion polymerization is easy to destroy so finding some methods to keep its stability should be paid special attention to control the mixing intensity.

In pharmaceutics, hairstyling, personal hygiene, and cosmetics, emulsions are frequently used. These are usually oil and water emulsions but dispersed, and which is continuous depends in many cases on the pharmaceutical formulation. These emulsions may be called creams, ointments, liniments (balms), pastes, films, or liquids, depending mostly on their oil-to-water ratios, other additives, and their intended route of administration.[10][11]The first 5 are topical dosage forms, and may be used on the surface of the skin, transdermally, ophthalmically, rectally, or vaginally. A highly liquid emulsion may also be used orally, or may be injected in some cases.[10]Popular medications occurring in emulsion form include calamine lotion, cod liver oil,Polysporin,cortisolcream,Canesten, andFleet.

Microemulsions are used to deliver vaccinesand kill microbes.[12]Typical emulsions used in these techniques are nanoemulsions of soybean oil, with particles that are 400-600nm in diameter.[13]The process is not chemical, as with other types of antimicrobial treatments, but mechanical. The smaller the droplet the greater the surface tension and thus the greater the force required to merge with other lipids. The oil is emulsified with detergents using a high-shear mixer to stabilize the emulsion so, when they encounter the lipids in the cell membrane or envelope of bacteria or viruses, they force the lipids to merge with themselves. On a mass scale, in effect this disintegrates the membrane and kills the pathogen. The soybean oil emulsion does not harm normal human cells, or the cells of most other higher organisms, with the exceptions of sperm cells and blood cells, which are vulnerable to nanoemulsions due to the peculiarities of their membrane structures. For this reason, these nanoemulsions are not currently used intravenously (IV). The most effective application of this type of nanoemulsion is for the disinfection of surfaces. Some types of nanoemulsions have been shown to effectively destroy HIV-1 and tuberculosis pathogens on non-porous surfaces.

3. Objectives

3.3.1 In this experiment, the first objective is to find the relationship of drop size and stirring intensity. In most cases, an increase in stirring intensity will cause an decrease in the size of every droplet inside of the oil-in-water emulsion. In order to keep the stability of the system, a fixed concentration of surfactant (SLES) will be added in each experiment to keep a balance between the forces in both directions. Furthermore, the quantity of SLES used in every system should be kept the same. Besides, the time for this kind of experiments is not enough to carry out all, so only one type of the agitator will be investigated. Therefore, the parameters which can be changed are the speed of the agitator, the oil viscosity and different time intervals.

2. The second objective is to link droplet size to the viscosity of oil. Different concentration and viscosity of oil may render the emulsion system unstable with respect to time, because different oil viscosity means different Reynolds number showing different flow regime that the emulsion is. And thus the other important properties of the emulsion should be affected by the mean viscosity of the oil phase and water phase.

3. The third objective is to investigate the effect of concentration of aqueous phase have on the droplet size.

4. At the same time, the mixing time can influence the size of the oil droplet and its distribution. So that is another meaningful point to investigate.

4. Methodology

Viscosity of the oil is: 10, 1000,12500and 30000 cSt.

The agitator rotor can run from 10000 to 20000 RPMs for a rotor stator system.

5. Resources requirements

6. Laboratory Safety

The author has attended an introduction about health and safety and will obey all rules in the lab. While working with lots of harmful chemicals, I have read the instruction of chemical use which provides some vital information in case of emergency. All the cutters using by stirring operations must be assessed before use. Lab coat, safety glasses and nitrile rubber gloves should be dressed in case of potential danger. I have been working safety in the lab for about half a year in my college and I claim that I have known what I should do for emergent situation and decrease the degree of danger to the least.

7. Work plan

8. Beneficiaries

9. References