EPS and EPP production process
The technique used to produce EPS and EPP is actually very simple. First, liquid monostyrene and propylene are produced from crude oil. Then, via a number of production steps, the actual raw materials are made: expanded polystyrene and polypropylene.
Polymerisation reaction of the monomer 'styrene'
Polymerisation reaction of propylene (also called propene)
The EPS beads are small, glass-like globules that are inserted with a small quantity of the blowing agent pentane. The pentane, which is similar to natural gas, is heated with steam to cause the bubbles to expand, thereby forming EPS beads with a size up to 50 times the original volume. The blowing agent escapes from the beads, and the numerous cells in each bead fill with air.
When the feather-light, resilient beads are heated with steam again, under pressure in a mould, they melt to form a homogenous EPS moulded part.
In contrast to EPS, EPP contains no pentane. The beads expand as a result of differences in the air pressure within the mould. Under the influence of steam, the beads melt together to form an EPP moulded part.
Thus an EPS or EPP part consists of thousands of beads that have been melted together. The air is trapped in the beads and can no longer escape. This makes it an ideal shock-absorbent material for protecting products while they are en route to their final destination. And as the trapped air also makes it an excellent insulator, EPS moulded parts are also used extensively by the construction industry, for purposes such as the insulation of houses, and by central-heating system manufacturers in products such as boilers.
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The burning behaviour of EPS:
favourable in comparison to other materials
Like carton, corrugated cardboard and paper, EPS is flammable. The speed with which these packaging materials burn does not differ much. However, EPS variants containing fire-retardants are also commercially available. These are often used in the construction industry and meet all the requirements for those applications.
In contrast to what many believe, studies have shown that the toxicity of the fumes released from burning EPS is significantly lower than that of many natural materials. TNO's Centre for Fire Safety , for instance,concluded in 1980 that the toxicity of the smoke from EPS - even in the case of uncontrolled burning - is less than that from natural materials such as wool, cork and even wood.
