How to Make EPS Foam

Impregnate the polystyrene resin granules with the blowing agent. When making EPS foam, Pentane Gas (C5H12) is normally used as the blowing agent. A small amount of pentane gas is injected into the resin in a process known as Polymerization.

Begin the pre-expansion process. After the resin granules have been impregnated, place them into your steamer and use steam to heat the granules. The heat will cause a reaction with the granules and the blowing agent, and will cause the polystyrene granules to expand to 50 times their original size. At this stage you have a large number of individual foam pellets that are ready to be molded.

Decide on what method of molding your will use on your EPS foam. There are two standard options for molding. The first method is to use a "shape molding" machine. This method will mold your foam to the precise size and shape of the product being developed. The second option is to use a "block molding" machine. Doing block molding creates large blocks or even sheets of EPS foam, which can later be cut to the size and shape that the customer requires. It is important to decide which method applies to the EPS foam you will make, so that you can choose an appropriate molding machine.

Pour the EPS granules into your mold and complete a second heating. The second time the granules are heated with steam, they will swell within the mold and become pressed together into one solid piece of foam. It is this mold heating process that transforms them from individual grains to a sheet of EPS foam.

Remove the EPS foam product from the mold and allow it to cool. The cooling time will depend on how large your foam item is. Allow the foam to sit and cool until it has reached room temperature. Inspect the mold for any cracks or damage before approving it for use.