Sub-Product

What is Expandable Polystyrene?

Expandable Polystyrene (EPS) consists of polystyrene micro-pellets or beads containing a blowing agent and other additives for foaming.^[1] 

EPS is generally produced in a Suspension Process by adding a Blowing Agent, usually Pentane.^[2] An alternative continuous Process consists in direct Injection of the Blowing Agent into the Polystyrene Melt, combined with subsequent Underwater Pelletization.^[1]

Expandable Polymeric Beads are a moulding Material in the form of Granules or Beads, approximately 3 mm in diameter. The Beads or Granules may contain between 5% and 8% of a volatile Hydrocarbon, chiefly Pentane.^[3]

How is Expanded Polystyrene Produced?

The Foaming Agent causes the Resin to foam during subsequent Moulding into Expanded Polystyrene. The Foaming Process may be performed as a single-step or a two-step Process:^[2]

• The two-step Process passes the Blowing Agent though the Polystyrene Beads during, or after, Polymerisation. The resultant Beads are then subjected to Steam Heating to above their glass transition temperature resulting in the Beads expanding (by 40 to 80 times) and produce the Cellular form. The resulting Product is then moulded.
• The one-step Process employs direct thermal Extrusion of the Material after Blowing and is mostly used for Sheet and Film Manufacture.

References

1. SULZER, Expandable polystyrene (EPS)
2. David Zhang, 13^th Mar 2021, Linkedin article, Manufacturing Processes of Expandable Polystyrene (EPS)
3. CargoHandbook, Expandable polymeric beads