EPS is one of the lightest of all construction materials allowing ease of handling and faster construction times. Its outstanding thermal insulation properties and durability ensure performance once used in any building or construction.
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EPS is manufactured from styrene monomer; low levels of styrene occur naturally in many plants, fruit, vegetables, nuts and meat. EPS is a derivative of ethylene and benzene and is made using a polymerization process which produces translucent spherical beads of polystyrene, about the size of sugar granules. During this process a low boiling point hydrocarbon, usually pentane gas is added to the material to assist expansion during subsequent processing.
EPS is produced in three stage process
Upon contact with steam the pre-foaming agent found within the polystyrene beads (usually a hydrocarbon such as pentane) starts to boil and the beads are expanded to between 40 to 50 times their original volumes.
After expansion the beads undergo a maturing period in order to reach an equilibrium temperature and pressure.
The beads are placed within a mold and again reheated with steam. The pre-foamed beads expand further, completely fill the mold cavity and fuse together. The beads are molded to form blocks or customized products. When molded, nearly all the volume of the EPS (~98%) is air.
There are two molding processes for EPS:
Block molding produces large blocks of EPS which can then be cut into shapes or sheets for use in both packaging and building/construction applications.
Shape molding produces parts which have custom designed specifications. Electronic product packaging in particular is where shape molded EPS is used extensively.
Recycling and Recovery
Expanded Polystyrene is completely recyclable.
EPS recycling process
EPS scrap must be segregated from other materials in the waste stream before it can be recycled. Ideally the EPS should be separated before it enters the waste stream to minimize contamination and so as to not take up bin capacity for other recyclable materials.
Since EPS is lightweight, transportation cost is a major component of its recycling. The material handling requirements for EPS scrap are usually determined by the recycler. Most commonly EPS scrap is either bagged in loose form or baled prior to transport.
The collected EPS is fed into a granulation machine. The granulated material is then fed to a hopper where it is stored before being compressed into continuous lengths. This compressed material is broken into lengths suitable for palletisation. Once palletised the material is ready for shipment.
Converting EPS into other products
Once exported, the EPS material is then shredded and then extruded to form General Purpose Polystyrene (GPPS) pellets. This can then be used as a feedstock for applications such as synthetic timber, CD cases, stationery products as well as plant pots and coat hangers.