Quick answer: Expanded polystyrene (EPS) is a lightweight, rigid cellular foam made by expanding polystyrene beads with steam inside a mold. It is roughly 98% air, offers good thermal insulation and impact protection, and is widely used in packaging, construction and consumer goods.

What exactly is expanded polystyrene?

Expanded polystyrene (EPS) is a closed-cell foam produced from expandable polystyrene beads. The beads contain a blowing agent; when they are heated with steam they expand up to 40–50 times their original volume and fuse together into a rigid, lightweight shape. This is why EPS is often described as around 98% air.

EPS is a specific type of polystyrene foam. It is different from extruded polystyrene (XPS), which is produced by extrusion and has a smoother, denser skin, and different from EPP (expanded polypropylene), which is made from a different base polymer.

Key properties of EPS

EPS is valued for three things: it is extremely light, it insulates well for its cost, and it absorbs shock. Those characteristics come directly from the air trapped inside its closed cells.

Why density matters

Density is the single most important specification for EPS. A 15 kg/m³ grade is soft and light, ideal for protective packaging; a 30 kg/m³ grade is firmer and better for construction insulation and load-bearing applications. Choosing the right density keeps both cost and performance in balance.

Common types and grades

EPS is supplied in several forms. Moulded EPS shapes are produced in a mold and used for packaging and construction blocks. EPS blocks are cut into sheets, boards and profiles. Specialised grades include flame-retardant EPS for construction, graphite EPS for higher insulation performance, and high-density EPS for structural parts.

Where EPS is used

Packaging

EPS protects televisions, washing machines, electronics, food and fragile goods during transport. Custom EPS molds produce packaging that fits a product precisely — see our EPS packaging molds.

Construction

EPS blocks and panels insulate walls, roofs and floors. Waffle pods, ICF blocks and lightweight fill all rely on moulded EPS.

Agriculture and consumer goods

Seed trays, fish boxes and insulated containers use EPS for its light weight and insulation. Moulded EPS is produced from tooling such as EPS molds.

How EPS is made

Manufacturing EPS has four main steps: pre-expansion of beads, maturing in a silo, moulding with steam inside a mold, and drying/cutting. The mold — usually aluminium — determines the final shape and surface finish. Our guide to the EPS/EPP mold production process explains each stage.

EPS vs EPP and XPS

If you need repeated impact resistance or higher heat tolerance, EPP is usually the better choice — see the difference between EPS and EPP.

Frequently asked questions

Is expanded polystyrene the same as Styrofoam?

Not exactly. Styrofoam is a brand of extruded polystyrene (XPS) made by Dow. EPS and Styrofoam are both polystyrene foams, but EPS is expanded from beads while XPS is extruded, giving it a different structure and surface.

Is EPS recyclable?

Yes. EPS carries resin code 6 and can be densified and recycled into new polystyrene products. Collection and infrastructure vary by region, which is why EPS is often landfilled even though it is technically recyclable.

Is EPS strong enough for structural use?

High-density EPS can carry significant loads and is used in construction blocks and even lightweight fill. Low-density packaging grades, however, are designed for cushioning rather than load bearing.

What density of EPS should I choose?

For protective packaging, 15–25 kg/m³ is typical. For construction insulation and load-bearing parts, 25–35 kg/m³ is more common. The right grade depends on the loads and insulation targets of your project.

Related products and guides

• EPS Mold Manufacturer
• EPS Packaging Molds
• EPS Raw Materials
• The Difference Between EPS and EPP