Foam consists of a solid or liquid that has trapped pocket of gas inside. There are many types of foam, which can be loosely categorized as closed-cell and open-cell. In closed-cell foam each gas bubble is full enclosed in its own cell. Solid foam material with closed -cells are not be easily compressible. In an open-cell foam there are no discrete cells. Instead, there is continual connected space throughout the material. Open-cell foams, like sponges, are able soak up water to some degree. They are as flexible as the material they are made from. Sometimes a closed-cell foam will also have some open-cells, meaning it will soak up liquids to some degree.
Though the word ‘Foam’ can be applied to many objects people often use the word to refer to expanded polystyrene (EPS). This is also known as ‘Styrofoam’, even though ‘Styrofoam’ is a trademarked name.
Expanded Styrofoam is light and reasonably rigid, idea for padding, packing and protection. It is basically closed-cell and water resistant, but not perfectly so. It has some open-cell properties and will soak up some liquids over time. If any water in the EPS freezes the material will tend to break apart; this is due to the water inside expanding as is becomes ice. But while this breaks the EPS into smaller pieces it does not rid the environment of the basic polystyrene material itself. Polystyrene, EPS or otherwise, must be recycled, usually with an EPS Recycling Machine.
Expanded polystyrene was independently invented by American and Swedish engineers in about 1940. Originally intended to replace rubber, which was in short supply because of the military demand of the day, it ended up being used for many different purposes. The accumulation of EPS and polystyrene products in the environment is an ongoing concern, but recycling the material (by turning it into new products), or breaking it down into its component, prevents the environmental pollution.
Transport of polystyrene, especially EPS, is difficult as the material is quite bulky, even as it weighs very little. EPS equipment is often used to compress Expanded Polystyrene in order to reduce the bulk for transport to the recycling facility.