What EPS is and how packaging is made from it

EPS stands for expanded polystyrene. The raw material consists of small polystyrene beads containing a blowing agent. The beads are first pre-expanded with saturated steam, increasing their volume 20 to 50 times, then left to mature, and finally heated again in a mould with steam nozzles, where they expand further and fuse into the final shape. The finished material is about 98 % air enclosed in cells and only 2 % polystyrene.

The density of EPS usually ranges from 10 to 35 kg/m³. Compressive strength and the weight of the pack both increase with density. Thermal conductivity is around 0.032–0.037 W/(m·K), depending on density.

In the industry, custom shapes are made in two ways:

• Moulding – For medium-sized and large runs. A mould has to be made first; the parts it produces are then dimensionally identical.
• Cutting from a block – No mould needed; for small runs, prototypes, boards and cut pieces. The shape is cut out of the block, for example with a hot wire.

Which route is suitable for a particular order is assessed according to quantity and shape.

Types of EPS packaging

• Insulated box – A box with a lid that insulates the contents. Cooling is provided by a coolant, such as gel packs or dry ice, added according to the nature of the shipment.
• Polystyrene box – A light, rigid box for storage and dispatch, without a moulded insert.
• Moulded part – An insert or retention part with cavities and grooves that follow the geometry of the product, used on its own or inside a cardboard box.

Insulated boxes and polystyrene boxes are available in standard sizes; moulded parts are made to measure.

Thermal insulation

EPS does not cool by itself; it only slows down heat exchange with the surroundings. How long a shipment holds its temperature depends on the wall thickness, the type and amount of coolant, the outside temperature, how full the box is, how often it is opened and the length of the route. There is therefore no universal number of hours. Where temperature is critical, measure it on the actual route, ideally in both summer and winter. For shipments with a prescribed temperature range, such as pharmaceuticals, the box and coolant are verified by a temperature profile test, for example to ISTA 7D and 7E.

Mechanical protection

On impact, the cell walls gradually deform and absorb the energy. A moulded part supports the product only at points that can structurally take the load and leaves the rest free. The bearing area is designed according to weight: an area that is too small is compressed all the way through on impact, while one that is too large is too stiff to absorb the shock. A heavier product therefore needs a larger bearing area, not just thicker walls all round.

EPS is made for a single trip. After a heavy impact it stays permanently compressed, so more resilient foams are better suited to returnable packs that must withstand repeated shocks.

Points to watch

• Insulation is not cooling – Size the amount of coolant according to the length of the route and the season.
• Dry ice is dangerous goods (UN 1845, class 9). It releases carbon dioxide as it sublimates, so the pack must not be sealed airtight, and the shipment must be marked as required for the mode of transport.
• Temperature and solvents – Under long-term load, EPS withstands about 75–80 °C. Acetone, petrol and other solvents, as well as some adhesives, dissolve it.
• Crumbling – Beads can come loose from the edges and cling to the product. This is a problem in clean environments and with glossy surfaces.
• Static charge – Standard polystyrene builds up a charge. Antistatic and conductive EPS grades exist for sensitive electronics; otherwise components belong in an ESD bag. Please state this in your enquiry.
• Food and pharmaceuticals are subject to special requirements. State in your enquiry which documents you need for the packaging.
• Volume of empty boxes – Straight-walled insulated boxes do not nest, so a stock of empty boxes needs warehouse space.

EPS or another material

EPS handles insulation and cushioning at the same time. When temperature does not matter, other materials are often more suitable. PE foams are flexible, return to their shape after an impact and do not crumble, which makes them suitable for painted surfaces and repeated use. Moulded pulp and paper honeycomb are paper packaging that the recipient puts into paper recycling, but they provide no thermal insulation. Air cushions and loose fill fill empty space but neither hold nor insulate the product.

What to send with your enquiry

• What the pack needs to handle: temperature, impacts or both
• Product dimensions or model, weight and the points where it can be supported
• For an insulated box: inner dimensions or volume, route length, required temperature range and type of coolant
• Number of items per shipment and expected annual quantity
• Requirements for documents or an antistatic version

Frequently asked questions

How long will an insulated box keep frozen goods frozen?

There is no universal figure – the box is insulation, not a refrigerator. Holding time depends on wall thickness, coolant, outside temperature, how full the box is and how often it is opened. The reliable approach is to measure the temperature on the actual route and adjust the box or the amount of coolant based on the results.

How do I choose the size of an insulated box?

According to the number of items per shipment, the volume of coolant and whether the box needs to fit into an existing cardboard box or be stacked on a pallet. Please state the required inner dimensions and the number of items per shipment.

Can you provide EPS packaging made to measure for our product?

Yes, custom moulded parts are part of our range alongside insulated boxes and polystyrene boxes in standard sizes. Send us the dimensions or model of the product, its weight, the support points and the expected quantity.

Is EPS suitable for packaging electronics?

For mechanical protection, yes. The limitation is static charge: unprotected boards and components belong in an ESD bag or an antistatic version, while the EPS moulding provides retention and cushioning.

How does the recipient dispose of the pack?

Clean polystyrene without labels, adhesive tape or food residue goes into the yellow plastics container or to a municipal collection yard; its recycling code is PS 6. Bulky boxes are broken up before disposal. If the pack should end up in paper recycling, consider moulded pulp or paper honeycomb.