Identification

• Styrofoam originates as styrene pellets. Styrene is one of the most common plastics seen in daily life. It is the material used in the clear plastic DVD cases, plastic toy models, and plastic silverware. Because of the source, Styrofoam is also known as expanded polystyrene.
  
  

Production

• Styrene beads are heated and expanded with what is known as a blowing agent. The process injects the blowing agent into the beads, until the final product is about 90 percent air. Styrofoam becomes very lightweight, but depending upon the process, it can have a compression strength greater than 60 psi.
  
  

Blowing Agents

• Different blowing agents are used in the process of making Styrofoam.
  Originally, the blowing agents were volatile hydrocarbons. Typical blowing agents were n-butane, n-pentane and isopentane. These were flammable, and the process started using chloroflurohydrocarbons (CFCs) as the blowing agents.
  
  

Environmentally Friendly

• The CFCs were found to be ozone-depleting substances, and most manufacturing processes are no longer using them because of their effects on the environment. Some Styrofoam manufacturers switched back to n-pentane and isopentane, but carbon dioxide is now also used as a blowing agent. The choice of blowing agent is particularly important when making Styrofoam for the food industry, like plates and cups. There is a danger of the chemicals leaching out of the container and into the food.
  
  

Forming Styrofoam

• There are two general methods of forming Styrofoam into final shapes. The first is known as steam chest molding, where steam is used to expand the styrene pellets inside of a mold. The steam causes the styrene to expand, taking on the final shape of the mold. The second method is known as extrusion. Extrusion is the process whereby the expanding foam is passed through an opening and formed into sheets. This method makes the Styrofoam sheets found in hardware stores and hobby shops.