Expanded Polystyrene

Description

Literally translated, polystyrene is "polymerised styrene".  The expandable form (known as EPS) is initially produced as small beads containing a blowing agent.  The beads expand when treated with steam, forming a lightweight "prefoam" of the required density.
These prefoamed beads are then processed in a mould to form large blocks that are then cut into sheets or other shapes.  Alternatively, for high volume products, the beads are moulded into their final product form in individual moulds. 

Typical Applications

Cold storage insulation: floors, walls, ceilings.  Lagging: pipes, tanks, vessels, valves and ductwork insulation.  Industrial and domestic insulation: floors, walls, ceilings and roofs.  Building and construction: concrete fill and for expansion joints.  Insulated panels and door manufacture: core insulating material.  Packaging: for maintaining the temperature of perishables or the protection of fragile goods.

Properties

Chemical Resistance
Resistant to: brine, fresh water, weak mineral acids, strong mineral acids (except concentrated nitric), weak alkalis, strong alkalis, most vegetable oils.  Non-resistant to: mineral oils, chlorinated hydrocarbons, petrol, benzine, esters and ketones.

Burning Characteristics
EPS is a combustible material.  The amount of heat liberated by EPS undergoing combustion is very small and if this is dissipated then sustained ignition is unlikely.  The 'FR' grades are treated with a fire retardant which causes the material to shrink away from a source of ignition without burning if exposed for a short period, but burns if kept in contact with the flame for a longer period.

Flame Retardant Grade (FR)
Flame retardant polystyrene (FR Grade) is available in all densities.  Surface fire index results according to SABS 0177, part III yeild the following results:
Spread of flame index 4,4.  Heat contribution index 0,9.  Smoke emission index 9,9.  Surface fire index 4,7.  Class 5.

Characteristic Properties of EPS