How is expanded polystyrene (EPS) foam made?
Styrene is composed of Benzene (liquid) and Ethylene (gas), both of which are petroleum products. EPS begins as a styrene monomer which goes through a process where the styrene monomers link into larger molecules called polystyrene. Expanded polystyrene or EPS foam is made from polystyrene pellets or beads that are puffed up with steam. The process is similar to cooking rice with steam. Usually a small amount (approx 4%-6%) pentane or another “blowing agent” is added to the hard polystyrene pellets to enable the expansion process. When these independent foam beads are in a mold they take the shape of the mold and hold that shape when they dry and cool down. The polystyrene beads grow to more than 40 times their original size and when the process is complete the usable EPS is about 98% air* which gives it features that are desired. Expanded polystyrene is a rigid, insulating, light weight, and biologically friendly foam. *source: European Manufacturers of Expanded Polystyrene: www.eumep
