Difference Between Expanded and Extruded Polystyrene

The key difference between expanded and extruded polystyrene is that we produce expanded polystyrene (or EPS) from solid beads of polystyrene while we produce extruded polystyrene (or XPS) from solid polystyrene crystals.

Expanded polystyrene is a type of foam made from polystyrene. It is a lightweight, rigid and closed cell insulation. Extruded polystyrene is another form of foam made from polystyrene. The trademark name for this product is Styrofoam (by The Dow Chemical Company). Both these materials are thermoplastic and rigid.

1. Overview and Key Difference
2. What is Expanded Polystyrene
3. What is Extruded Polystyrene
4. Side by Side Comparison – Expanded vs Extruded Polystyrene in Tabular Form
5. Summary

What is Expanded Polystyrene?

Expanded polystyrene or EPS is a thermoplastic foam material that we produce from solid beads of polystyrene. In the production of this foam material, we can achieve the expansion due to the trapped small amounts of gas inside the polystyrene beads. This gas expands when we heat the material. In order to heat the material, we use steam. This heating process forms closed cells of EPS. After the expansion, these beads increase their volume by 40 times than the original volume of the bead.

Difference Between Expanded and Extruded Polystyrene

Figure 01: Expanded Polystyrene Foam

About 98% of expanded polystyrene is air. Therefore, it is one of the lightest packaging material. This makes the transport costs minimum. The most favourable properties of this polymer material include excellent thermal insulation, damping properties and extreme lightweight. These properties make it useful as building materials, packaging material, model planes, etc. However, there are some drawbacks as well. For example, it is not resistant to organic solvents, it is flammable if oil painted, health concerns when using as a packaging material for food items, etc.

What is Extruded Polystyrene?

Extruded polystyrene or XPS is a foam material that we produce from solid polystyrene crystals. Therefore, in the production process, we need special additives and blowing agents along with polystyrene crystals. We feed these components into an extruder. There, the mixture combines perfectly and melts under controlled conditions such as high temperatures pressures. This results in a viscous plastic fluid, which is hot and thick. Then we pass this fluid through a die. When it emerges through the die, it expands forming a foam. Then we can shape, cool and trim this material into the desired shape.

The production process of extruded polystyrene results in a unique foam product. It has a uniform closed-cell structure and smooth skin. This material has a superior moisture resistance. Therefore, it is useful in construction and engineering applications. Moreover, it has excellent chemical resistance, soil compatibility, the ability of outdoor storage, etc.

What is the Difference Between Expanded and Extruded Polystyrene?

Expanded polystyrene or EPS is a thermoplastic foam material that we produce from solid beads of polystyrene whereas the extruded polystyrene or XPS is a foam material that we produce from solid polystyrene crystals. This is the key difference between expanded and extruded polystyrene. When considering the production processes, the expanded polystyrene has a minimum harmful effect on the environment than the extruded polystyrene.

The below infographic presents the difference between expanded and extruded polystyrene in tabular form.

Summary – Expanded vs Extruded Polystyrene

The short-term for expanded polystyrene is EPS, and for extruded polystyrene, it is XPS. The key difference between expanded and extruded polystyrene is that we produce expanded polystyrene from solid beads of polystyrene while we produce extruded polystyrene using solid polystyrene crystals.

Reference:

1. Johnson, Todd. “How Does EPS Play a Role in Your Daily Life?” ThoughtCo, ThoughtCo. Available here
2. “What Is Expanded Polystyrene (EPS) Foam? The Possibilities Are Endless!” Insulation Corporation of America. Available here