Closed cell foam sheets are a strong material family to compare when you need a firm, reusable insert for a flight case, tool case or equipment case. Cross-linked polyethylene holds a more defined shape than soft open cell packaging foam and has low water uptake, which can be useful for equipment that is transported, stored and handled repeatedly.
This guide focuses on material selection rather than repeating our general case-layout advice. All Foam currently supplies AFP30 and AFP45 cross-linked polyethylene sheets online, and the main decision is how much rigidity and load-bearing resistance the insert actually needs.
Quick answer: what closed cell foam should I use for a flight case?
AFP30 is a sensible starting point for many lighter case inserts, liners and separators. AFP45 is denser and provides greater resistance under load, so it becomes more relevant for heavier equipment, narrow support points or inserts that need additional rigidity. Thickness, cavity design and the way the item is supported are just as important as density.
Why polyethylene foam is used in flight cases
A flight case insert needs to do more than look tidy. It may need to locate equipment, prevent movement, protect finished surfaces and maintain usable cavities after repeated removal and replacement.
Closed cell polyethylene can be useful because it has:
- a firm sheet structure
- clean, defined edges when cut carefully
- low water uptake compared with open cell foam
- useful resistance to compression
- low weight compared with solid plastic or rubber blocks
- a choice of sheet thicknesses
Specialist UK flight-case suppliers also commonly use closed cell polyethylene in reusable equipment inserts. That does not mean every PE grade performs the same way, so the All Foam product specification still needs to be matched to the case.
How this differs from our existing flight case guide
All Foam already has a guide to foam sheets for toolboxes, flight cases and drawer inserts. That article covers measuring, layout and general insert planning across different foam types.
This article answers a narrower question: when you have decided that a firm closed cell polyethylene insert is appropriate, should you choose AFP30 or AFP45, and what else needs to be considered?
AFP30 for lighter protective inserts
AFP30 has a nominal density of 30 kg/m³. It is the lighter general-purpose cross-linked polyethylene grade in the current All Foam range.
It can be a useful starting point for:
- lighter tools
- sample and presentation cases
- instruments with broad support areas
- case liners
- separators
- removable protective pads
The advantage is not that AFP30 is "soft". It is still a rigid closed cell polyethylene sheet compared with typical open cell packaging foam. The benefit is that it can provide a structured insert without the additional resistance of AFP45 where that is not needed.
AFP45 for heavier or more demanding case work
AFP45 has a nominal density of 45 kg/m³ and greater load-bearing resistance than AFP30.
That can make it relevant where:
- equipment is heavier
- a small foot or edge creates a concentrated load
- thin insert walls need greater support
- repeated use places more stress on the cavity
- the insert must resist deformation around a dense component
The higher-density grade should still not be selected automatically. A very rigid insert can be less forgiving around a delicate product, and density does not replace adequate thickness.
The AFP30 vs AFP45 closed cell foam guide compares the two grades in more detail.
Density and thickness solve different problems
One of the most common case-building mistakes is to treat density and thickness as interchangeable.
Density affects how much material is present within the foam and influences resistance under load. Thickness gives the insert physical depth and available compression distance.
A thin AFP45 layer is not automatically a better protective solution than a deeper AFP30 layer. The correct design depends on the item, case dimensions and support geometry.
Our packaging foam thickness guide explains why item weight, fragility, clearance and journey conditions all need to be considered together.
Start with the equipment, not the foam sheet
Before choosing a material, inspect the equipment that will go into the case.
Record:
- overall dimensions
- weight
- strong load-bearing surfaces
- fragile controls, screens or connectors
- protruding feet or handles
- parts that must remain accessible
- accessories travelling in the same case
Support the strongest parts of the item rather than forcing pressure onto delicate features.
A heavy component resting on four small feet behaves differently from a broad item with the same total weight because the load is concentrated into a smaller area.
Plan the case cavity carefully
The foam cavity should locate the item without requiring excessive force to insert or remove it.
Useful design details include:
- enough wall thickness around the item
- clearance around knobs and connectors
- finger spaces for removal
- support beneath strong parts of the equipment
- separation between accessories
- lid clearance when the case is closed
Very thin foam walls can tear or fold, especially next to a heavy component. Sharp internal corners can also create weak points.
If the case is moulded or tapered, measure at the level where the foam will actually sit rather than relying on the maximum opening dimensions.
Base foam, side foam and lid foam do different jobs
A case insert is a small system.
The base carries weight. Side walls reduce sideways movement. Lid foam can help control vertical movement when the case is closed.
That means one thickness does not have to perform every job.
For example, a case may need a deeper base insert to support the item but only a thinner side liner where the aim is surface protection. Do not over-compress the contents simply to make the lid feel tight.
Moisture behaviour in reusable cases
Closed cell polyethylene is often chosen where low water uptake is useful.
All Foam describes AFP30 as waterproof and non-absorbent. AFP45 has a stated maximum water absorption of 1% by volume.
That can be beneficial in reusable cases that may encounter damp workshops, vehicles or storage environments. It does not make the complete case waterproof.
Water can still enter around the case lid, hinges, seals and fittings. Moisture can also be trapped against equipment if a wet item is packed away without drying.
The foam is only one component in the protection system.
What about electronics and static-sensitive equipment?
Do not assume ordinary closed cell polyethylene is suitable for every electronic device.
If the equipment or component has an electrostatic discharge requirement, use packaging designed for that purpose rather than relying on a general black foam insert.
All Foam's Packaging Foam range includes specialist anti-static foam for suitable electronics packaging. The anti-static foam for electronics packaging guide explains the difference.
Colour alone is not proof of anti-static performance.
Should the insert be glued into the case?
Not always.
The current AFP30 and AFP45 sheets are supplied without self-adhesive backing. That allows the case maker to test the fit before deciding whether the layers need to be retained permanently.
A removable insert can be useful if:
- the equipment layout may change
- the case needs cleaning
- damaged foam may need replacement
- the case is used for more than one configuration
If layers or liners need bonding, select a fixing system that is compatible with both the foam and the case substrate.
Read the foam without adhesive backing guide for more on removable and fixed installations.
Cutting and layering closed cell foam
A flight case insert can be made from one deeper block or from several layers, depending on the required cavity and available sheet thickness.
Layering can make it easier to build stepped recesses or create a separate base and top layer. Before bonding layers, dry-fit the complete stack and check:
- total height
- lid clearance
- cavity depth
- item removal
- access to connectors
- wall thickness around cut-outs
Use sharp tools and a protected cutting surface. Test difficult cuts on an offcut first.
For repeated or commercial inserts, consistent templates or machine conversion may be more appropriate than freehand cutting.
When is open cell packaging foam better?
Closed cell polyethylene is not automatically the best material for every flight case.
Soft open cell packaging foam can be useful where the item needs more compliant cushioning or where the case is intended to compress gently around irregular shapes.
The choice depends on fragility, item weight, journey conditions, repeated use and the way the case is handled.
The closed cell polyethylene packaging guide gives a broader comparison of structured PE foam in protective packaging.
A practical AFP30 vs AFP45 decision
Use AFP30 as the first comparison where the case needs a clean, firm insert for lighter or medium-duty equipment and there is no reason to add extra rigidity.
Move towards AFP45 where the item is heavier, contact areas are smaller or the insert must resist greater deformation.
Then choose thickness from the actual case geometry. Leave enough material around cavities, protect delicate features and test the fit before permanent fixing.
Quick answer: is higher density always better for a flight case?
No. AFP45 offers greater load-bearing resistance, but AFP30 can be the more suitable choice for lighter items and general inserts. The best design balances density, thickness, cavity shape, equipment weight and the strength of the surfaces being supported.
Related All Foam guides
For the next step, compare AFP30 and AFP45, read the broader toolbox and flight case foam guide, and use the packaging foam thickness guide when planning the finished insert.
