Expanded polystyrene foam is made in a five-step process, beginning with pre-expansion and aging of the raw materials. The process continues through curing with heat, molding the material into a solid mass and then into shapes, and ending with fabrication for construction or packing applications.
In the first stage, the raw material resin used to form EPS foam comes in small beads, which then are swollen up to 50 times their original size through steam heating and expansion of pentane gas that has been impregnated inside every bead. The beads are then dried and sent on to the curing process.
Using heat speeds up the curing process and creates a completely dry product. Once the material is cured, it is molded into blocks or bricks for easy fabrication use. A vacuum molding process is sometimes used to create the finished blocks. Steam is used again to allow the beads to expand further and completely fill the vacuum mold.
Some beads are sent for shape molding, where the beads are expanded into molds of specific shapes.
EPS foam pieces manufactured in blocks or bricks often require trimming or cutting to desired specifications.
The manufacturer then sends finished EPS foam pieces off for many uses. Preshaped foam pieces are used for packaging, insulated concrete forms or even coffee cups. These pieces are usually used for fabrication work such as thermal insulation. EPS foam products are recyclable but not biodegradable.