About Polystyrene
Polystyrene is one of the most widely used plastics in the world. Understanding its properties, types, and lifecycle is the first step toward making informed recycling decisions.
What is Polystyrene?
Polystyrene is a versatile synthetic polymer made from styrene monomer, classified under resin code #6. It is a thermoplastic, meaning it can be repeatedly melted and reformed without significant degradation.
First discovered in 1839 by Eduard Simon, a German apothecary, polystyrene remained a laboratory curiosity until commercial production began in the 1930s. It quickly became one of the most produced plastics globally.
The brand name Styrofoam is actually a registered trademark of Dow Chemical Company, specifically for their extruded polystyrene (XPS) insulation product. The white foam cups and containers commonly called "Styrofoam" are actually expanded polystyrene (EPS), a different product entirely.
EPS vs XPS
The two main forms of polystyrene foam have distinct properties and recycling challenges.
Expanded Polystyrene
The familiar white, lightweight foam made of pre-expanded polystyrene beads fused together. Contains up to 98% air, making it extremely lightweight but bulky. Most commonly seen in disposable cups, food containers, and packaging peanuts.
Characteristics
Common Uses
- Disposable coffee cups
- Food takeout containers
- Packaging peanuts
- Protective product packaging
- Coolers and ice chests
- Seedling trays
- Craft and hobby materials
- Insulated shipping containers
Extruded Polystyrene
A denser, more rigid foam produced through an extrusion process. Typically colored (blue, pink, or green depending on manufacturer). Primarily used in construction for insulation boards and structural applications.
Characteristics
Common Uses
- Building insulation boards
- Foundation waterproofing
- Roofing insulation
- Cold storage facilities
- Crafting and modeling
- Structural insulated panels
- Highway and bridge construction
- Geotechnical fill material
Where It's Found
Polystyrene is used in a wide range of everyday products and industrial applications.
Cups & Containers
Disposable coffee cups, food takeout containers
Protective Packaging
Product cushioning, shipping materials
Building Insulation
Wall and roof insulation panels
Food Containers
Meat trays, egg cartons, deli containers
Coolers & Ice Chests
Portable coolers, cold chain packaging
Medical Supplies
Lab trays, medical packaging, test kits
Electronics
TV and computer protective packaging
Construction
ICF forms, geofoam, decorative molding
Industry at a Glance
How Polystyrene is Made
The manufacturing process from raw petroleum to finished polystyrene products.
Raw Material
Styrene monomer is derived from petroleum through the dehydrogenation of ethylbenzene.
Polymerization
Styrene monomer undergoes polymerization to create solid polystyrene beads or pellets.
Expansion (EPS)
For EPS, beads are impregnated with pentane gas and then expanded with steam to 40-50x their original volume.
Molding
Expanded beads are molded into final shapes using steam chests and custom molds under controlled conditions.
Extrusion (XPS)
For XPS, polystyrene is melted and forced through a die with a blowing agent to create dense, uniform foam boards.