Polystyrene polymer is the substance used to make thermocol geofoam. Large containers containing this polystyrene resin "bead" are supplied, and it is fed into a hopper during manufacture. It is basically a thermoplastic that is malleable and can take on multiple shapes. Made from post-consumed recycled content, the Geofoam material is 100% recyclable. Essentially, one can reheat it and reconstitute it as many times as you’d want. Heat and pressure are used in a mould to generate polystyrene through a process known as polymerization. Densities of Expanded Polystyrene or Geofoam can vary depending on the amount of heat and pressure applied to the bead inside the mould.
There are various ways that EPS Geofoam differs from "Styrofoam," as it is more widely known. Even though EPS geofoam will physically resemble Extruded Polystyrene, or Styrofoam, one of the main distinctions between the two foam building materials is how EPS Geofoam is made as opposed to how its "cousin," XPS or Styrofoam, is made.