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Using Moulding Expanded Polystyrene in Injection Moulding

by | Sep 16,2019 | Plastic Injection Molding

The main reasons for using Expanded Polystyrene in Injection Moulding are due to its durability light weight and insulating properties. Multiple products for many sectors are able to be produced, especially ones that are required to maintain products at a certain temperature in the food storage or preparation industries. Other benefits associated with the insulated, lightweight materials occur when being carried in a logistical or customer friendly format, as discussed below.

This being the case, it would be expected that the material would only be used in the above packaging situations, but this is not, in fact, the case. It is often to be found covering white and other consumer electronic goods that require protection from heat and moisture, which is a very novel and large scale use for a packaging type that appears to be only useful for foodstuffs! Another leading reasoning for Expanded Polystyrene to be used in this way, as mentioned above, is that it also provides excellent physical protection to the devices that are packed within and its robust nature allows stacking and storage to be undertaken without any damage occurring to the contents.

So, how is it produced? Well, in contravention to other members of the thermoplastics family, there are some pre-processes that must be undertaken prior to using the material for injection moulding purposes. Initially, the beads of resin are expanded by around forty times their original size using steam. This causes a vacuum inside the beads, which retain their now larger size after being held in a tank to allow the pressure in the pellet to equalise with the external atmospheric pressure. The pellets are now reheated with steam to create the final product, which can then be moulded in aluminium tools with the application of steam to assist the moulding process.

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