Closed cell foam sheets can be considered for cool-box liners and insulated packaging because their closed-cell structure limits water uptake and creates a low-density layer between the contents and outer wall. All Foam's AFP30 and AFP45 technical sheets also list insulation among typical applications. However, All Foam does not publish an R-value or thermal conductivity for these grades.
Quick answer
AFP30 or AFP45 may be useful as part of an insulated box or protective liner where their actual properties suit the design. They should not be used to promise a specific holding time or temperature without testing the complete container, lid, joints, coolant arrangement and contents.
A cool box is a complete thermal system
A sheet of foam is only one part of the heat path.
Heat can enter through:
- walls
- lid
- corners
- hinges
- handles
- fasteners
- gaps
- seals
- openings during use
A well-insulated wall cannot compensate for a poorly fitting lid.
That is why the performance of the complete box matters more than the word "insulated" on one material.
Why closed-cell PE is considered
Closed-cell polyethylene is useful in damp environments because it has low water uptake compared with many open-cell cushioning foams.
For All Foam's current grades:
- AFP30 has a nominal density of 30 kg/m3 and is described as waterproof and non-absorbent
- AFP45 has a nominal density of 45 kg/m3 and a maximum water absorption value of 1% by volume
Both are rigid cross-linked polyethylene sheets.
That combination can make them useful as protective, wipeable structural liners where the complete application is appropriate.
What the data does not tell us
The current All Foam data sheets do not provide:
- thermal conductivity
- R-value
- a cool-box holding time
- a validated cold-chain profile
- food-contact certification
- pharmaceutical packaging approval
Those missing claims are important.
Do not copy a lambda value from another polyethylene foam and present it as AFP30 or AFP45 data.
Do not treat AFP30's WRAS approval for cold-water use as food-contact approval. They are different specifications.
Consumer cool boxes
For a general-purpose picnic or storage box, a closed-cell liner may help create a separated layer around the contents.
A practical design should consider:
- enough foam coverage
- close-fitting corners
- lid overlap
- durability around the opening
- drainage and cleaning
- whether the lining is removable
- how ice packs or frozen bottles are held
- whether sharp containers can cut the foam
The box still needs realistic expectations. A DIY lining is not automatically equivalent to a purpose-built high-performance cooler.
Insulated shipping boxes
Temperature-sensitive parcels introduce more variables.
The pack can include:
- outer carton
- insulated liner
- coolant
- product payload
- void fill
- data logger
- sealed inner bag
- orientation controls
The ratio between coolant and product, ambient conditions and journey time can change performance significantly.
If a shipment must remain inside a defined temperature range, the system needs to be qualified for that requirement.
Pharmaceutical and medical cold chain
This is where caution is essential.
A general closed-cell PE sheet should not be promoted as pharmaceutical cold-chain packaging simply because polyethylene foam is used somewhere in that industry.
Medical or pharmaceutical shipments can require:
- defined temperature ranges
- qualification protocols
- validated packing instructions
- traceability
- controlled refrigerants
- monitoring
- specific cleanliness or material requirements
Use a validated system designed for the product.
All Foam sheet material may be one raw material considered by a packaging engineer, but it is not a complete validated medical shipper.
Food-contact considerations
Water resistance does not prove food-contact suitability.
If food will touch the foam directly, the exact material needs the appropriate food-contact documentation for that use.
A separate sealed food container inside an insulated box is a different situation from placing unpackaged food directly against the foam.
Do not infer food approval from colour, closed-cell structure or WRAS approval.
Lids are often the weak point
A box may have thick side walls but lose useful performance through the lid.
Check:
- lid fit
- compression
- gaps at corners
- hinges
- latches
- damaged seals
- repeated opening
A removable foam lid pad can be useful in some designs, but it should not prevent the box closing properly.
If the lid has a large uninsulated bridge, adding more foam to the base may deliver little benefit.
Joints and corners
Mitred, butt-jointed or layered corners all create different heat paths and fit issues.
For a simple workshop build, aim for repeatable close joints without excessive compression.
Where quantified thermal performance is required, use an engineered construction and appropriate test method rather than relying on visual tightness.
AFP30 versus AFP45
AFP45 is denser and has higher compression resistance than AFP30 under the published test.
That may be useful where the liner also carries more mechanical load.
It does not prove that AFP45 has a better thermal insulation value.
For a cool-box liner, the decision should consider:
- required rigidity
- wall space
- mechanical wear
- impact exposure
- thickness
- full thermal design
Density is not a substitute for thermal-conductivity data.
Bonding liners into a box
AFP30 and AFP45 are supplied unbacked.
If they are permanently fixed, use a bonding system specifically suitable for polyethylene and the box substrate.
Permanent bonding can make damaged liners harder to replace.
A removable liner or mechanically retained panel may be a better option where the box needs regular cleaning or future replacement.
Condensation and cleaning
Cold contents can create condensation.
Design the box so moisture does not become trapped indefinitely behind a liner.
After use:
- empty the box
- remove standing water
- clean using methods compatible with all materials
- dry before closing for storage
- inspect for cuts and contamination
Do not assume low water absorption means the complete box cannot become damp.
Testing a DIY or commercial cool box
For a non-critical personal use, a simple practical temperature test can show whether the box meets your own expectation.
For a commercial or specified requirement, document:
- payload
- coolant
- starting temperatures
- ambient temperature
- test duration
- opening events
- sensor positions
- pass/fail limits
Repeat the test under the expected worst-case conditions.
Quick answers
What foam is best for a cool box? A suitable closed-cell insulation material can be considered, but the best choice depends on the required thermal performance, space, cleaning, mechanical load and certification.
Can AFP30 or AFP45 line a cool box? They can be considered as closed-cell PE liner materials, but All Foam does not publish an R-value or holding-time claim for either grade.
Is closed cell foam waterproof in a cooler? AFP30 is described as waterproof and non-absorbent, and AFP45 has low stated water absorption. Joints and the complete box can still admit or trap water.
Can I use it for pharmaceutical shipping? Do not rely on ordinary sheet foam as a validated cold-chain system. Pharmaceutical shipments should use packaging qualified for the required temperature profile.
Is AFP30 food safe because it is WRAS approved? No such inference should be made. WRAS cold-water approval is not the same as food-contact certification.
