Moulding Expanded Polystyrene (EPS)

 

This process page is kindly sponsored by the member companies of the BPF EPS Packaging Group

 

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Properties

Durable
The exceptional durability means that it can effectively protect a wide range of goods. There is no loss of strength in damp conditions, making EPS ideal for cool-chain food products. The fact that the material is moisture resistant also means that the highest hygiene requirements are met.

 

CD player with protective packaging

Lightweight
EPS is made up of 98% air. Due to its extremely low weight, its use as a packaging material minimizes the total product weight. This reduces transportation costs compared with other packaging materials. In turn this means that transport fuel consumption is improved and vehicle emissions are minimized. All contributing to lower global warming. Insulating
The thermal insulation properties help keep food fresh through the distribution chain. It is widely used to package fish and for seed trays where low heat loss assists in the growth of the plants.

Overview

Expanded polystyrene (EPS) is used for the production of a number of applications. However its major application is as a protective packaging for consumer electronic products and white goods. Its excellent thermal insulation and mechanical protection properties make it ideal to package fish and other foodstuffs. EPS also has applications in horticulture as seed trays.

The outstanding shock absorbency of expanded polystyrene packaging ensures the protection of a broad range of products. Moreover, its compression resistance means that EPS is ideal for stackable packaging goods. When safety is paramount, EPS comes into its own. It is used in the manufacture of children's car seats and cycling helmets, where its protective qualities, strength and shock-absorbency are vital.
 

The Production and Moulding Process

Unlike other thermoplastic processes, the production of EPS products requires that the raw materials be pre-conditioned prior to their final "tooled" moulding process.
The raw material (also known as "expandable polystyrene" or "bead") has a sperical shape and is similar to sugar in appearance.

The conversion process is carried out in three stages:

Pre-expansion
The tiny spherical polystyrene beads are expanded to about 40 times their original size using a small quantity of pentane (typically 5% by weight) as a blowing agent. This process involves the heating of beads, using a flow of steam, which causes the blowing agent to boil and thus a honeycomb of closed cells is formed. Maturing
As the material cools the pentane liquefies and a partial vacuum is formed inside the bead. The beads are returned to a holding tank for approximately twelve hours to allow the pressure differential to equalize, giving a stabilised granule. Final Forming
In this final stage the pre-expanded stabilized beads are reheated with steam in a mould. The final expansion takes place and the beads coalesce to give a shaped moulding. This can also be used to form large blocks which can be sectioned to the required shape as panels, boards, cylinders etc. In this final form the EPS is made up of 98% air.

The Machines and Tools

The components are formed in aluminium mould tools. These are generally of male and female form, with the shape between the two halves of the mould being the shape, being produced.

The mould tool is fitted into a press, which has the facility to introduce steam from behind each half of the tool. The steam is introduced through small slotted vents, which have been machined into the mould tool when it was manufactured.
 

Surfboards and body protection in moulded eps.
Head protection moulded in eps.
Medicine phials in protective packaging.

EPS and the Environment

EPS packaging is a thermoplastic polymer based on styrene, (which also occurs naturally in products such as strawberries and coffee beans.) It does not, and never has contained CFCs or HCFCs. The small proportion of hydrocarbon blowing agent used readily decomposes in the atmosphere, and as a result EPS does not have any adverse impact on the ozone layer.
 

About the BPF Expanded Polystyrene Packaging Group

The Expanded Polystyrene (EPS) Packaging Group is part of the British Plastics Federation and represents over 85% of the EPS moulding industry in the UK.

An objective of the Group is to raise awareness about the excellent combination of protection, cost-effectiveness and environmental performance that EPS can offer. Another objective is to increase the recycling of used EPS packaging and to promote awareness of existing recycling schemes through a programme of newsletters and seminars.

 

Contact a Plastics Packaging Supplier

If you are looking for a supplier of plastics packaging, please complete your details below and the BPF will send the detail, on your behalf, to the most relevant companies within the plastics industry who will contact you directly with more details.

 

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