How To Make EPS Foam

Pile of EPS foam

Eduard Simon discovered polystyrene in Berlin in 1839. Commercial manufacture of polystyrene began in Germany in 1951, and in 1959, a company in Pittsburgh, Pennsylvania developed polystyrene foam.

Polystyrene is chemically inactive, meaning that it does not react to the any of the materials that it comes in contact with. This is the reason why it is suitable to be used as chemical, solvent and food containers. It is basically produced in three forms, as (a) extruded polystyrene (PS) like the CD jewel cases and plastic cutlery, (b) as expanded polystyrene foam (EPS) for packaging, (c) as extruded polystyrene foam (XPS) for insulation, model building and crafts.

Foam is defined as “a mass of small bubbles formed in or on a liquid”. It also means “a lightweight material in cellular form, made by introducing gas bubbles during manufacture”.

Expandable Polystyrene (EPS) foam is manufactured through that process. EPS foams are durable lightweight plastics used for product packaging of electrical appliances such as a television, ice boxes, and helmets. Sheet foam and block foam are used in construction.

EPS is one of the most common uses of polystyrene. It is made from expanded polystyrene beads, usually white, and can be molded into many forms as protective packing material for fragile items. You can see them whenever you buy toys, big and small electrical appliances and equipment and other items that need a rigid casing before being inserted in cardboard boxes. Surfboards are also made from EPS foam. Likewise, foam cups used in hot liquid dispensing machines are made from molded EPS.

Making expandable polystyrene foam is a two-step process.

  1. Polystyrene beads are placed in a pre-expander and impregnated with pentane gas, an expansion agent. The expanded polystyrene is produced through the process of polymerization when the gas is added, with a mixture of 90-95% polystyrene and 5-10% pentane. The solid polystyrene beads are pre-expanded/prepuff into foam when heated by steam. The beads can expand up to fifty times its original size when in comes in contact with steam heat.
  2. The next step is either to mold the pre-expanded foam or turn them into sheets of foam. The pre-expanded foam in poured into a shape molding machine and reheated by steam until the foam beads fuse together and form its final density and required shape. The block molding machine for sheet foams and foam blocks contains 98% air volume and only 2% of the polystyrene, making the product very lightweight.

New regulations, formulation and manufacturing process ensure that EPS has no chlorofluorocarbons (CFC’s) making it safe. Pure hydrocarbon gases like pentane and butane are used in the manufacture of expandable polystyrene foams. Small pieces of EPS can be mixed with soil to improve ventilation and aid organic substances to break faster. It can also be mixed with concrete to increase its insulating properties and reduce its weight. With sufficient air supply, you can burn EPS foam to replace fuel required for combustion. One kilo of EPS is equal to 1.2 to 1.4 liters of fuel oil saved.


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