Difference Between Suspension and Emulsion Polymerization

Main Difference – Suspension vs Emulsion Polymerization

Polymerization is the process of forming polymers by combining monomers. A monomer is the building block of a polymer. Monomers should have either unsaturated bonds or at least two functional groups per molecule in order to undergo polymerization. Polymers are giant, macromolecules. There are several different forms of polymerization. Suspension polymerization and emulsion polymerization are such forms. The main difference between suspension and emulsion polymerization is that suspension polymerization requires a dispersing medium, monomer(s), stabilizing agents and initiators whereas emulsion polymerization requires water, monomer and a surfactant.

Key Areas Covered

1. What is Suspension Polymerization
– Definition, Requirement, Advantages
2. What is Emulsion Polymerization
– Definition, Requirement, Advantages
3. What are the Similarities Between Suspension and Emulsion Polymerization
– Outline of Common Features
4. What is the Difference Between Suspension and Emulsion Polymerization
– Comparison of Key Differences

Key Terms: Dispersing Medium, Emulsion, Initiator, Monomer, Polymer, Polymerization, Surfactant, Suspension

What is Suspension Polymerization

Suspension polymerization is a type of radical polymerization in which mechanical agitation is used. Here, the monomers should be in the liquid phase. There can be either one monomer or several monomers present in the liquid mixture. When polymers are formed from this method, the polymer material exists as a sphere suspended in the liquid.

The liquid phase is often water, but other suitable organic solvents can also be used. Almost all the thermoplastic polymers are formed from this polymerization technique. Some of the polymer materials produced by this method include PVC (polyvinyl chloride), styrene resins, PMMA (polymethyl methacrylate), etc. The essential components of a suspension polymerization reaction mixture are as follows.

Dispersing medium
Monomer or monomers
Stabilizing agents
Monomer soluble initiators

Suspension polymerization has many advantages over other polymerization methods: the liquid phase act as an effective heat-transfer medium, it is highly economical and more environmentally friendly. The temperature and viscosity of the medium can easily be controlled. In addition, the purification and the further processing is also easy when compared to other polymerization techniques.

What is Emulsion Polymerization

Emulsion polymerization is a form of radical polymerization that usually starts with an emulsion. This emulsion is composed of water, monomer and a surfactant. The most common form of emulsion used in this technique is oil-in-water emulsion. There are droplets of monomer that are emulsified in water. There are few requirements for emulsion polymerization to occur:

The monomer should be water insoluble
Monomer should be polymerizable by free radicals
Water should be present as the dispersing agent
A surfactant should be used as the emulsifier
A water-soluble initiator should be used for the initiation of the emulsion polymerization process

Difference Between Suspension and Emulsion Polymerization

Figure 1: Emulsion Polymerization Process

There are several advantages of using emulsion polymerization: it can be used to make high molecular weight polymers in a short time period, water is used as the dispersing agent (this enables the fast polymerization without any loss of temperature control), the final product can be used as it is and generally it does not have to be altered or processed further.

Similarities Between Suspension and Emulsion Polymerization

Both are forms of free radical polymerization techniques
Both types give high-quality polymer materials

Definition

Suspension Polymerization: Suspension polymerization is a type of radical polymerization in which mechanical agitation is used.

Emulsion Polymerization: Emulsion polymerization is a form of radical polymerization which usually starts with an emulsion.

Requirements

Suspension Polymerization: The essential components of a suspension polymerization reaction mixture are dispersing medium, monomer(s), stabilizing agents and initiators.

Emulsion Polymerization: The emulsion polymerization requires water, monomer and a surfactant.

End Product

Suspension Polymerization: In suspension polymerization, the polymer exists as a sphere suspended in the medium after the formation.

Emulsion Polymerization: In emulsion polymerization, the formed polymer can easily be separated and purified.

Advantages

Suspension Polymerization: Suspension polymerization is highly economical and more environmentally friendly.

Emulsion Polymerization: Emulsion polymerization can be used to make high molecular weight polymers in a short time period.

Conclusion

Polymerization is the process of producing a polymer material. Suspension polymerization and emulsion polymerization are two types of polymer producing techniques. The main difference between suspension and emulsion polymerization is that the requirements for suspension polymerization are dispersing medium, monomer(s), stabilizing agents and initiators whereas the requirements for emulsion polymerization are water, monomer and a surfactant.

Reference:

1. polymerdatabase.com, CROW © 2015. “Polymer Properties Database.” Suspension Polymerization, Available here.
2. “Emulsion.” The Polymer Science Learning Center, Available here.
3. “Suspension polymerization.” Wikipedia, Wikimedia Foundation, 7 Jan. 2018, Available here.

Image Courtesy:

1. “Emulsion Polymerization Cartoon 3” By Firesine at English Wikipedia – Transferred from en.wikipedia to Commons. (Public Domain) via Commons Wikimedia