Expanded polystyrene or EPS is a closed cell, resilient, lightweight, rigid cellular plastics material produced in a range of densities between 10kg/m3 and 35kg/m3. One of the main applications for products manufactured from EPS are thermal insulation systems such as pipe insulation.

Expanded polystyrene is supplied as plastic beads in which an expanding agent, usually pentane, has been dissolve. In the presence of steam the thermoplastic polystyrene softens and the increasing vapour pressure of the expanding agent causes the beads to expand up to 50 times their original volume. During this stage the degree of expansion is controlled to achieve the desired density.

Expanded polystyrene does not contain any ozone depleting substance and none is used in its manufacture.

From the pre-expander the beads are gently transported to large hoppers for ageing. The time of ageing is set to cool and stabilise the beads and allow for infusion of air to replace the expanding agent in the cells. The beads are charged into a closed mould where they are further expanded and fused together by steam heating. The freshly moulded blocks of EPS are passed through temperature controlled ovens to remove moisture and the final traces of the expanding agent and to provide blocks of constant dimensional stability.

It is from these blocks that the pipe sections are cut to suit the various pipe sizes and R value.