Polystyrene Sheets: Difference Between Expanded and Extruded

Design-oriented sustainability and energy-efficiency are key reasons in finding the appropriate insulation materials to use. There are two types of rigid polystyrene sheets for insulation used in the building and construction industry today: expanded polystyrene sheets (EPS) and extruded polystyrene sheets (XPS).

Extruded Polystyrene Sheets (XPS)

Extruded polystyrene sheets are manufactured using an extrusion process. Just like expanded polystyrene sheets, XPS are formed from a basic granule of polystyrene resin. The thermoplastic granules are put into an extrusion machine, a device that uses a push or pull method of materials through a shaped die to form a continuous length of product with a pre-set cross section. In manufacturing, the extrusion process provides numerous benefits like having a broad range of complex cross sections and the ability to produce delicate materials.

In the extrusion machine, polystyrene resins are liquefied and mixed with additives to form a viscous fluid. A blowing agent is then used to induce the mixture's expansion. The polystyrene mixture goes through a die that moulds the polystyrene compound into its preferred shape, using controlled heat and pressure conditions. The rigid closed cell structure forms according to its final dimensions or client specifications.

The closed cell structure of extruded polystyrene sheets directly impacts its longevity and durability. XPS has low water absorption rate since its cell walls are closed, leaving no void or space for water or moisture to infiltrate. Since water can't penetrate extruded polystyrene sheets, they can maintain their structural integrity. Ideal to use in different insulation applications like below-ground.

When properly installed, extruded polystyrene sheets improve the structure's energy efficiency by providing a complete perimeter insulation. This process helps in retaining the slab's warmth, thereby reducing heat loss through a building's foundations. Aside from below-ground insulation, extruded polystyrene sheets are placed over the roof membrane for insulation. This method of putting polystyrene sheets is known as IRMA or inverted roof membrane assembly.

XPS contains high compressive strengths suitable for insulating heavy load floor applications such as warehouses, productions areas, and car parks. Extruded polystyrene sheets adapt well to uneven surfaces, absorbs peak loads, and is resistant to mould and other ground contaminants.

Expanded Polystyrene Sheets

The manufacturing process involved in creating expanded polystyrene sheets consists of three stages. In the pre-expansion stage, polymer resins are placed in pre-expander machines where steam is used to induce expansion of polymer resins of up to 40 times its original volume. This process turns the polymer resins into small closed cell structures that hold the air in their interior.

EPS beads are then cured and dried at the same time. In this stage of maturing, the polymer beads achieve superior mechanical elasticity and improved expansion capacity.

The stabilised pre-expanded polystyrene beads enter the third stage, where the second batch of steaming process will take place. This process results to polymer beads binding together. Large blocks of EPS are then moulded and sectioned according to the required dimension and shape.

Expanded polystyrene sheets are versatile in nature. It has different applications, such as food and product packaging, insulation, and arts and craft medium.

EPS has the following advantages:

Lightweight
Easy to handle and carry
Durable
Long-term R-value
Low water absorption rate
Shock absorbent
Low combustible material
Dimensionally stable
Recyclable

The use of extruded and expanded polystyrene sheets in the building and construction industry provides flexibility, compatibility, and thermal efficiency.

FOAMEX is Australia's innovator and leading supplier of extruded and expanded polystyrene sheets. Both XPS and EPS are traditional insulation materials for building construction, insulation, shipping and packaging, theatre and film production props and background design, signage and decorations.

Contact FOAMEX at 02 9773 1655 or visit their website at www.foamex.com.au for a complete list of their polystyrene sheet products.