Polyethylene and polyurethane are two common foam families used in protective packaging. Polyurethane packaging foam is often softer and more flexible. Polyethylene foam is often firmer, more structured and absorbs less water. The All Foam packaging foam sheets range includes both families so customers can choose by item, journey and case design.
Neither material is best in every situation. This guide compares their practical behaviour for boxes, flight cases, equipment, electronics and industrial parts.
What is polyurethane packaging foam?
Polyurethane packaging foam is usually a flexible open cell material. It can be supplied as flat sheets or with a convoluted egg crate profile.
It compresses readily and can provide soft cushioning around light and medium weight products. It is easy to cut into pads, liners and separators.
Common uses include:
- cardboard box lining
- briefcases and tool cases
- lid cushioning
- protective layers between products
- general transit packing
- convoluted contact foam
The exact firmness and density vary. Packaging grade polyurethane should not be treated as upholstery foam unless the product is specifically intended for furniture use.
What is polyethylene packaging foam?
Polyethylene packaging foam is commonly supplied in closed cell sheets, rolls or planks. It is often semi rigid, usually firmer than flexible polyurethane foam and able to retain a more defined shape.
It may be used for:
- reusable case inserts
- industrial components
- tool and instrument protection
- cases used in damp conditions
- presentation inserts
- structural separators
- protective pads
Polyethylene products can be cross linked or non cross linked and may be supplied in different densities, colours and thicknesses.
The main structural difference
Open cell polyurethane foam has connected cells that allow air to move through the material. It feels flexible and compressible.
Closed cell polyethylene foam has cells that are largely sealed. It is generally firmer and absorbs less water.
This difference affects cushioning, surface feel, cutting and environmental suitability.
For a wider material comparison, read the open cell and closed cell foam guide.
Cushioning feel
Polyurethane foam provides a softer response. It can wrap gently around an item and compress under light loads.
Polyethylene foam provides a firmer response. It can retain its shape and resist compression under higher loads, depending on the exact product.
A lightweight, delicate object may benefit from soft polyurethane contact. A heavy tool may need firmer polyethylene foam or a high load bearing support layer.
The final pack can combine materials. A firm base can be covered with a thin soft contact layer where surface protection is important.
Load support
Soft polyurethane foam can compress too far under a heavy item. When it bottoms out, the product may strike the hard case or box floor.
Polyethylene foam can offer greater structure, but the correct density and thickness still matter. A thin sheet can also bottom out beneath a concentrated load.
For heavy equipment, read the high load bearing packaging foam guide.
Moisture behaviour
Closed cell polyethylene foam generally has lower water absorption than open cell polyurethane foam. This can be useful in reusable cases, workshops and damp environments.
Polyurethane foam can absorb and hold moisture. It should be kept dry and allowed to ventilate if exposed.
Foam does not make the outer package waterproof. Water can still enter through the box, case seals or openings.
Surface and appearance
Flexible polyurethane packaging foam usually has a soft, textured surface. It is commonly dark charcoal in packaging applications.
Cross linked polyethylene foam can have a finer cell structure and smoother appearance. It may be available in several colours for presentation and colour coding.
Appearance should follow performance. A clean coloured insert is not useful if it is too firm, too thin or unsuitable for the product.
Flat and convoluted profiles
Polyurethane packaging foam is often available flat or convoluted. Flat sheets provide even contact. Convoluted sheets provide flexible peak contact and are often used in case lids.
Polyethylene foam sheets are normally flat and can be cut into cavities, layers and blocks.
The flat and convoluted packaging foam guide explains when each profile is useful.
Cutting and fabrication
Flexible polyurethane foam can be cut with a sharp knife or suitable foam cutting tool. It compresses during cutting, so accurate support and marking matter.
Polyethylene foam holds its shape more firmly and can produce defined edges. Thick sheets still need controlled cutting and may require specialist conversion for clean repeated shapes.
Rounded internal corners can help prevent tears. Leave enough material between cavities.
Adhesive backing
Some polyethylene foam sheets can be supplied with self adhesive backing. This can help when lining case walls or fixing protective pads.
Flexible polyurethane foam may be bonded with a suitable spray adhesive, but compatibility, ventilation and cure time matter.
Adhesive should not be treated as a universal solution. Check the foam, surface, temperature and intended service life.
Reusable packaging
Polyethylene foam is often chosen for reusable inserts because it can retain a defined shape. It can suit service cases, returnable industrial packs and tool control.
Polyurethane foam can also be reused, especially as a lid or contact layer. Its edges and surface should be inspected for wear and permanent compression.
The design should make replacement possible. Bonding every layer permanently can make a damaged section harder to repair.
Electronics and ESD requirements
Ordinary polyurethane and polyethylene foam are not automatically suitable for static sensitive electronics.
All Foam also lists pink anti static polyurethane packaging foam for relevant electronics applications. Specialist polyethylene foams can also be manufactured with ESD properties.
Use the required material category and data. The anti static foam guide explains the difference between general cushioning and electrostatic control.
Fire information
Neither foam family should be described as fire retardant without the exact product data.
Packaging foam is not a substitute for furniture grade foam. Where fire performance is required, check the technical information and the complete assembly.
Use the foam data sheets and contact All Foam if the application has a defined requirement.
Packaging light products
Light products such as samples, accessories and small instruments may use flexible polyurethane foam for soft contact and movement control.
Flat sheets can line the box. Convoluted foam can provide lid contact. A small cavity can locate the item.
Polyethylene may still be chosen where a clean presentation, moisture resistance or repeated use is important.
Packaging heavy products
Heavy products usually need careful load distribution. Firm polyethylene or high load bearing polyurethane packaging foam can support the base, while a softer contact layer can protect the surface.
Do not place the weight on a fragile cover or narrow projection. Support the frame or approved mounting points.
Allow enough thickness for compression and protect the sides as well as the base.
Packaging fragile products
Fragility is not the same as low weight. A light glass instrument may require more controlled cushioning than a heavier solid metal tool.
Polyurethane can provide a soft contact layer. Polyethylene can create a precise cavity. The best solution may use both.
Keep pressure away from lenses, screens, handles and decorative edges.
Storage versus transit
A storage tray may only need to prevent scratching and organise parts. A courier pack must manage drops, stacking and vibration.
Polyurethane may be sufficient for a stable storage box. Transit can require more thickness, stronger outer packaging and a more structured insert.
Choose for the real journey rather than the appearance of the finished pack.
Cost and material use
Material price depends on grade, thickness, sheet size and quantity. The cheapest sheet may not be the lowest cost if it causes damage or needs frequent replacement.
Avoid choosing a higher specification than the job needs. A very dense polyethylene insert may add cost without helping a light product. A thick, soft polyurethane pad may use space without providing enough load support.
The aim is the minimum suitable material that protects the product reliably.
Recycling and waste
Polyethylene and polyurethane follow different recycling routes. Local facilities vary, and foam may not be accepted in household collections.
Keep offcuts clean for possible reuse. Businesses should identify the exact material and ask a suitable waste contractor about collection.
Product protection also matters. Preventing damage and returns can reduce waste beyond the packaging material itself.
A practical comparison
Choose polyurethane packaging foam when you need:
- softer cushioning
- flexible box lining
- flat or convoluted contact
- easy layering
- protection for light or medium items
Choose polyethylene packaging foam when you need:
- a firmer structure
- defined reusable inserts
- lower water absorption
- protective blocks and separators
- a smooth or coloured presentation
Use a combination when the pack needs firm support and soft contact.
Questions before ordering
Record:
- product dimensions and weight
- fragile features
- internal box or case dimensions
- base, side and lid space
- moisture exposure
- reuse frequency
- anti static or fire requirements
- preferred thickness and backing
A prototype is sensible for valuable equipment or repeated production.
Key takeaway
Polyurethane packaging foam is generally softer, more flexible and useful for cushioning and lid contact. Polyethylene packaging foam is generally firmer, more structured and useful for reusable inserts, cases used in damp conditions and protective blocks.
Choose by considering the item, load, journey and available space. Use both materials where separate support and contact layers improve the result.
For help comparing the live All Foam options, send the item and case details through the contact page.