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Foamex - Innovative Polystyrene

What is Expanded Polystyrene (EPS)?

Foamex Expanded Polystyrene (polymerised styrene) is a rigid cellular plastic foam material derived from petroleum and natural gas by-products. Styrene is produced from benzene and ethylene, and is polymerised in the presence of catalysts, usually organic peroxides. The beads of resin are subjected to steam, which causes the thermoplastic polystyrene to soften and expand up to 40 times its original volume.

Once conditioned by ageing, the EPS beads are blown into a mould, and steam is used in the forming process. The EPS product is then dried and finished by a number of processes, such as hot wire cutting or lamination.

Fire Properties

Foamex blocks and sheets are manufactured from a fire retardant raw material and are not an undue fire hazard when correctly installed. The polystyrene will burn when in contact with a flame, like other organic building materials, but will self extinguish when the fire source is removed.


Foamex expanded Blocks are manufactured in seven grades to Australian Standard AS 1366 Part 3-1992. These grades relate to the density of the product, which affects their physical strength as well as the thermal resistance (R-Value). As the density increases so does the thermal resistance.

Long Term ‘R’ Value

Foamex expanded Polystyrene’s cellular structure means it is stable and will not settle. Installed correctly without damage it will not deteriorate with age and will deliver constant R values for the life of the building.


Expanded Polystyrene, when force-saturated to a moisture content of ten percent of volume, will retain 80% of its thermal value, therefore retaining the energy saving characteristics. When polystyrene is saturated with moisture, odours are not emitted and there is no nutritional value to support algae or fungi, thereby negating hazardous growths and decomposition.


CSIRO reports comment that when polystyrene is ignited, the toxicity of gases given off is “not greater” than that associated with burning timber. (H. Hofman & H Oettel Comparative Toxicity of Thermal Decomposition Products.)

Characteristics of Polystyrene

Foamex Polystyrene (EPS) is a durable, economical material with all of the following advantages;

  • Lightweight
  • Easy to handle
  • Durable
  • Strong & flexible
  • Long term R-value
  • Low water absorption
  • Shock absorbent
  • Vibration dampener
  • Buoyant
  • Comparatively inert
  • Low combustibility
  • No food value for insects & rodents
  • Dimensionally stable
  • Recyclable

Polystyrene Grades and Thermal Conductivity

Thermal conductivity for our expanded polystyrene sheet grades is shown in the reference below.

 SL Grade  k = 0.041 W/mk*
 S Grade  k = 0.0397 W/mk*
 M Grade  k = 0.0383 W/mk*
 H Grade  k = 0.0368 W/mk*
 VH Grade  k = 0.0352 W/mk*
 * k value @ reference temperature 25°C


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