Expanded polystyrene foam (also known as EPS) is a durable material that can be used in many consumer products. You can find it in almost every place, including your local grocery store (plates and cups), and local electronics stores (insulation to refrigerators, coolers, etc). It's also a great insulation material.
EPS foam begins at very small beads. Also known as granules. These small beads must be "blown" into larger beads to create an EPS foam block. This is approximately 50 times the original size. This is known as pre-expansion. The beads are blown depending on their density using steam from an expander, or steamer.
An expander is a machine where a worker inserts the raw material and turns on the steam. It can also be an automated machine that blows the stems automatically. The beads, which can be up to 50 times larger than their original size, are now called pellets. They are ready for molding.
Continuous pre-expanders can be operated without pressure. They are equipped with an open-top agitator tank that continuously feeds raw material from the bottom using an adjustable screw conveyor. Through openings located just above the tank, steam is also continuously fed into the pre-expanding area.
No matter what pre-expander they use, all of them trickle the expanded beads into the fluid bed dryer. The beads are dried and stabilized before being transported to the storage silos.
There are two options for molding. The first is to use a mold molding machine that shapes the foam into the desired shape. Another option is to use a block molding machine, which can create foam sheets or blocks measuring 3'x2'x8' and up to 5'x5'x24'.
For second heating with steams, the EPS expanded beads are poured into the molding machine. The foam beads will be swelled by being pressed against one another until they form one solid piece.
Pentane or carbon dioxide is the most commonly used blowing agent. Polymerization is a process that fills polystyrene's air pockets with millions of air bubbles. This allows it to expand and gives it low thermal conductivity. The product can be molded to a variety of sizes and shapes during expansion. Although the final product is 90% air it can be compressed to a strength of up to 40 psi.