EPS foam starts with small granules like sand in a fabric called polystyrene. The raw material is called styrene. Styrene can be found just about anywhere, at your local grocery store and local electronics store. The foam products generally depends on the density of raw materials.
All plastic utensils are made of styrenes, such as CD cases and cloth hangers. EPS, which is expanded polystyrene, begins as small pearls. The next step in the process is "blowing" these tiny beads into even larger beads, about 50 times larger than the original beads.
Depending on the desired density, the pearls are blown with the help of steam in a machine called an expander.
The expander can be a simple machine where the worker fills the raw material and then turns on the steam or an automatic machine where the material is automatically weighed over the steam, then activated (automatically), and then turned off.
At this point, the size of the pearl is up to 50 times larger than its original size.
The primary expander operates continuously without pressure and is equipped with an open-lid mixer, through which raw materials are continuously fed from below via an adjustable screw conveyor. The "steam" is also continuously supplied to the pre-expansion chamber through the hole just above the bottom of the container.
The so-called "second pass expansion" of the foaming pre-expander is equipped with a very large screw conveyor to transport the foamed materials back for fumigation. What all pre-expanders have in common is that the fully expanded granules flow into a so-called fluidized bed dryer, where they are dried and stabilized before being transported to a storage silo.