Expandable polystyrene is made by polymeristion of a Styrene monomer, (Styrene being a oil derivative.) The polymer is named Polystyrene. Polystyrene is widely used for single use cups and spoons and such like and is responsible for about 10% of the total plastic use. The unique properties of EPS, (Expandable Polystyrene), are achieved by mixing Pentane with the polymer. Pentane is a natural gas made from carbon and hydrogen. When decomposed it will form carbondioxide and water, which plants and various microorganisms will feed upon. When Pentane is introduced to temperatures of around 100°C, it increases its volume significantly and suddenly, thus the EPS areound will become "puffed" as Pentane tries to escape the its confinding environment. The result is a larger EPS bead filled with tiny air pockets.
The most traditional method of expanding the bead is using steam and by lenthening the time that steam is applied one can alter the density of the expanded bead. When combined in a mould and subjected to furher steaming the beads will expand ever further and take the shape of the mould they were subjected to. The insulation properties of the EPS are due to the previously mentioned air pockets in the expanded bead and subsequently EPS is extremely light and has a very high strenght to weight ratio as it is in effect 98% air. EPS does not contain any "heavy metals", no sulphur or chlorine and no CFC, (Chloroflurocarbons) are formed during production or reduction of EPS. EPS packaging is 100% recycleble