What is EPS Foam?


Polystyrene is a polymer made from the monomer styrene, a liquid hydrocarbon

that is commercially manufactured from petroleum by the chemical industry.

At room temperature, polystyrene is normally a solid thermoplastic, but can

be melted at higher temperature for molding or extrusion, then resolidified.

Styrene is an aromatic monomer, and polystyrene is an aromatic polymer.


Polystyrene was accidentally discovered in 1839 by Eduard Simon an

apothecary in Berlin, Germany. From storax, the resin of Liquidambar

orientalis, he distilled an oily substance, a monomer which he named styrol.

Several days later Simon found that the styrol had thickened, presumably

due to oxidation, into a jelly he dubbed styrol oxide ("Styroloxyd").

By 1845, English chemist John Blyth and German chemist August Wilhelm von Hofmann

showed that the same transformation of styrol took place in the absence of oxygen.

They called their substance metastyrol. Analysis later showed that it was chemically

identical to Styroloxyd. In 1866 Marcelin Berthelot correctly identified the formation

of metastyrol from styrol as a polymerization process. About 80 years went by before

it was realized that heating of styrol starts a chain reaction which produces

macromolecules, following the thesis of German organic chemist Hermann

Staudinger (1881 - 1965).

This eventually led to the substance receiving its present name, polystyrene. The I.G. Farben company began manufacturing polystyrene in Ludwigshafen, Germany, about 1931, hoping it would be a suitable replacement for die cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a heated tube and cutter, producing polystyrene in pellet form.


Pure solid polystyrene is a colorless, hard plastic with limited flexibility. It can be

cast into molds with fine detail. Polystyrene can be transparent or can be made

to take on various colors. It is economical and is used for producing plastic model

assembly kits, plastic cutlery, CD "jewel" cases, and many other objects where a

fairly rigid, economical plastic of any of various colors is desired.


Polystyrene's most common use, however, is as expanded polystyrene (EPS).

Expanded polystyrene is produced from a mixture of about 90-95% polystyrene

and 5-10% gaseous blowing agent, most commonly Pentane or carbon dioxide.

The solid plastic is expanded into a foam through the use of heat, usually steam.

Extruded polystyrene (XPS), which is different from expanded polystyrene (EPS),

is commonly known by the trade name Styrofoam.

The voids filled with trapped air give it low thermal conductivity. This makes it ideal as a construction material and it is therefore sometimes used in structural insulated panel building systems. It is also used as insulation in building structures, as molded packing material for

cushioning fragile equipment inside boxes, as packing "peanuts", as non-weight-bearing

architectural structures (such as pillars), and also in crafts and model building,

particularly architectural models. Foamed between two sheets of paper, it makes

a more-uniform substitute for corrugated cardboard, tradenamed Fome-Cor. A

more unexpected use for the material if as a lightweight fill for embankments

in the civil engineering industry.

Expanded polystyrene used to contain CFCs, but other, more environmentally-safe

blowing agents are now used. Because it is an aromatic hydrocarbon, it burns with

an orange-yellow flame, giving off soot, as opposed to non-aromatic hydrocarbon

polymers such as polyethylene, which burn with a light yellow flame.


Production methods include sheet stamping (PS) and injection molding (both PS and HIPS).


The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon

connected to a Phenyl group (an aromatic ring similar to benzene).


EPS foam can be molded into different shapes -

1. EPS blocks are usually 4' x 3' x 8' or 4' x 4' x 8'

2. EPS shapes (molded)















3. EPS Surfboards





















Cutting EPS foam

Expanded polystyrene is very easily cut with a hot-wire foam cutter, which is easily made

by a heated and taut length of wire, usually nichrome due to nichrome's resistance to

oxidation at high temperatures and its suitable electrical conductivity. The hot wire

foam cutter works by heating the wire to the point where it can vaporize foam immediately

adjacent to it. The foam gets vaporized before actually touching the heated wire,

which yields exceptionally smooth cuts.


Polystyrene, shaped and cut with hot wire foam cutters, is used in architecture models,

signs, props for amusement parks, movie sets, airplane construction, and much more.

Such cutters may cost just a few dollars (for a completely manual cutter) to tens of

thousands of dollars for large CNC machines that can be used in high-volume industrial production.


Polystyrene can also be cut with a traditional cutter. In order to do this without ruining

the sides of the blade one must first dip the blade in water and cut with the blade at

an angle of about 30º. The procedure has to be repeated multiple times for best results.


Polystyrene can also be cut on 3 and 5-axis CNC routers, enabling large-scale

prototyping and model-making. Special polystyrene cutters are available that

look more like large cylindrical rasps















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