Difference Between Suspension and Emulsion Polymerization

The key difference between suspension and emulsion polymerization is that mechanical agitation is used in suspension polymerization while emulsion polymerization usually occurs in an emulsion.  

Polymerization is the formation of a macromolecule via the combination of a small molecule named monomers. This macromolecule is a polymer. Therefore, monomers act as the building blocks of polymers. There are different ways that we can make these polymers. Suspension polymerization and emulsion polymerization are two such forms.

CONTENTS

1. Overview and Key Difference
2. What is Suspension Polymerization
3. What is Emulsion Polymerization
4. Side by Side Comparison – Suspension vs Emulsion Polymerization in Tabular Form
5. Summary

What is Suspension Polymerization?

Suspension polymerization is a type of polymerization in which we use mechanical agitation. It is a form of radical polymerization. The monomers we use in this process are in the liquid phase. We use a liquid mixture as the polymerization medium. This liquid mixture may contain one or more monomers according to the chemical structure of the polymer that we are going to produce. The final polymer material forms in this process exist as a sphere that is suspended in the liquid medium. Therefore, it requires further alterations before using.

Most often, the liquid phase is an aqueous medium. But sometimes, we may use organic solvents as well. We can make almost all the thermoplastic polymers using this polymerization method.

The requirements for this polymerization to proceed are as follows;

• Dispersing medium
• Monomer(s)
• Stabilizing agent
• Initiators

Examples of the polymers that we can make using this technique include PVC (polyvinyl chloride), styrene resins, PMMA (polymethyl methacrylate), etc. Moreover, there are many advantages to this method as well. For example, the liquid medium we use in this technique acts as an effective heat transfer medium; thus it is highly cost-effective and environmentally friendly. In addition to that, we can easily regulate the temperature of the reaction medium.

What is Emulsion Polymerization?

Emulsion polymerization is a type of polymerization that usually occurs in an emulsion. The most often used form is an oil-in-water emulsion. It is also a type of radical polymerization.

The requirements for this technique are as follows:

• Water (as the dispersing agent)
• Monomer (this should be water soluble and be able to polymerize from free radicals)
• Surfactant (as the emulsifier)
• The initiator (should be water soluble)

This technique has several advantages; we can use this process to get a high molecular weight polymer in a short time. Since we use water as the dispersing medium, it allows polymerizing fast without losing the temperature control. Moreover, the final product of the polymerization does not need any alteration; we can use it as it is.

What is the Difference Between Suspension and Emulsion Polymerization?

Suspension polymerization is a type of polymerization in which we use mechanical agitation. Emulsion polymerization is a type of polymerization that usually starts with an emulsion. This is the key difference between suspension and emulsion polymerization. More importantly, the requirements of suspension polymerization includes a dispersing medium, monomers, stabilizing agent and initiators. Whereas, the requirements of emulsion polymerization includes water, monomers, initiator and a surfactant. Moreover, the end product of suspension polymerization requires alterations because it exists as a sphere that is suspended in the liquid medium. But, unlike suspension polymerization, the end product of emulsion polymerization does not require any alterations; we can use it as it is.

The below infographic presents the difference between suspension and emulsion polymerization in tabular form.

Summary – Suspension vs Emulsion Polymerization

There are many methods for forming polymers. Suspension and emulsion polymerization are two such methods. The difference between suspension and emulsion polymerization is that the requirements for suspension polymerization include a dispersing medium, monomers, stabilizing agent and initiators whereas the requirements for emulsion polymerization includes water, monomers, initiator and a surfactant.

Reference:

1. “Suspension Polymerization.” Wikipedia, Wikimedia Foundation, 13 Aug. 2018. Available here  
2. “Emulsion.” Bear Lab. Available here 

Image Courtesy:

1.”Polyvinyl chloride (PVC) production from suspension polymerization”By Cjp24 – Own work, (CC BY-SA 4.0) via Commons Wikimedia  
2.”Emulsion Polymerization Cartoon 3″By Firesine at English Wikipedia (Public Domain) via Commons Wikimedia