Expanded Polystyrene (EPS) foam is a lightweight, rigid, and cost-effective insulation material made from solid polystyrene beads. It is widely used for thermal insulation in construction as well as for protective packaging.
EPS is different from XPS (extruded polystyrene) in its manufacturing process, which gives it distinct properties. EPS has a less dense, bead-like structure with small air gaps between the fused beads, while XPS has a uniform, dense structure.
How EPS is manufactured
The production of EPS foam involves three main stages:
- Pre-expansion: Small polystyrene beads are impregnated with a blowing agent, typically pentane. When exposed to steam, the beads soften and expand up to 40–50 times their original size.
- Maturing: The beads are aged in silos for 12 to 24 hours to stabilize. During this time, the beads cool, and air diffuses into the cells, replacing the blowing agent.
- Molding: The pre-expanded beads are placed into a mold and reheated with steam. This causes them to expand further and fuse together to form a solid block or a specific custom shape. The final product is about 98% air.
Key properties
- Lightweight: Because it is 98% air, EPS is very light, which makes it easy and safe to transport and install.
- Good thermal insulation: The millions of tiny air pockets trapped within the foam’s cellular structure make it an effective barrier against heat transfer.
- High strength-to-weight ratio: Despite being lightweight, EPS has excellent compressive strength, especially in higher density grades.
- Moisture resistance: EPS is water-resistant but not completely waterproof. The closed-cell beads do not absorb water, but moisture can pass through the small voids between the fused beads if the foam is exposed to water for extended periods.
- Cost-effective: EPS is one of the most budget-friendly rigid foam insulation options available.
Common applications
EPS is a versatile material used across several industries.
- Building and construction: Used for insulating walls, floors, and roofs. It is also employed as a lightweight void filler in civil engineering projects, like road and railway embankments.
- Packaging: Its shock-absorbing and cushioning properties protect fragile goods like electronics and appliances during shipping.
- Containers: Serves as thermal insulation for disposable hot and cold beverage cups and food containers.
- Decorative and art projects: Easily cut and shaped, it is popular for architectural models, stage props, and crafts.