EPP vs EPS vs EPO vs PU vs TPU: Which Foam Mould Should You Quote in 2027?

The material decision is not a purchasing detail. It determines the mould material, the steam chest design, the vent layout, the shrinkage allowance and the whole cost per part. Here is how we help customers settle that decision before a single line of tooling is cut.

The five families at a glance

EPS: still the cheapest way to hold a temperature

Expanded polystyrene remains the default for single-trip cold chain packaging. It offers the lowest bead cost and the highest insulation per kilogram, which is why fish, seafood, fresh produce and pharmaceutical shippers still specify it. The trade-off is brittleness: EPS crumbles under repeated impact and cannot be used for returnable loops. Moulds are simple cast aluminium, usually multi-cavity, and work best with thin uniform walls and generous venting.

EPP: the material that survived the shift to reusable packaging

Expanded polypropylene is where most of our automotive and e-commerce work sits today. It recovers shape after impact, tolerates repeated steam cycles, resists oils and chemicals, and is fully recyclable in existing PP streams. The catch is processing: EPP needs higher steam pressure, tighter cavity temperature control and more careful venting than EPS. A mould built to EPS standards will produce EPP parts with weak fusion and visible bead gaps.

EPO: the surface quality option

EPO blends polypropylene and polyethylene, producing a finer, more uniform cell. Parts come out with a smoother skin and better dimensional repeatability than EPP at the same density, which suits visible trays, electronic device packaging and premium cold-chain shippers. EPO is less resilient than pure EPP, so it is rarely the right choice for energy-absorbing structures.

PU: a different process, a different mould logic

Polyurethane is poured or injected, not steamed. Moulds are sealed aluminium tools with venting, heating or cooling channels and often self-skinning surfaces. There is no steam chest and no bead fusion, so a PU tool cannot be converted from an EPS tool, and vice versa. If your part needs soft-touch feel, variable wall thickness or over-moulded inserts, PU is usually the only workable route.

TPU: when the part must survive abrasion

Thermoplastic polyurethane foam is dense, tough and resistant to oils and hydrolysis. Shoe soles, industrial seals, roller coverings and sports protection dominate. Tools run hotter, tolerances are tighter, and steel inserts are common in high-wear areas. Volumes are usually lower than EPS or EPP, so tooling amortisation matters more than cycle time.

How the material changes the mould

Three design parameters move with the material, and they are exactly the ones that decide whether a quotation is realistic:

• Shrinkage allowance. EPS contracts roughly 0.4–0.7%, EPP 1.8–3.0%. A cavity cut for EPS will produce undersized EPP parts.
• Vent size and pattern. EPS needs fine, dense venting; EPP needs larger vent areas with plug-resistant geometry to handle higher pressure and longer cycle times.
• Steam chest volume. EPP and EPO demand a properly sized steam chamber and condensate drainage. Undersized chests add 20–40% to cycle time and inflate energy cost for the life of the tool.

Three questions that settle it

1. How many trips will the part make? Single trip → EPS. Returnable loop → EPP or EPO.
2. Does the part have to absorb energy? Yes → EPP. No, only insulate → EPS.
3. Is the surface visible to the end customer? Yes → EPO or PU with a self-skinning surface.

Answer those three and the material, the mould material and the target price band follow almost automatically. Our engineering team reviews drawings against all five families before quoting, so the number you receive is the number you can actually build.

Contact us for a material recommendation and a mould quotation: WhatsApp / Phone: +86 19942010686 Email: bainuo@bainuomould.com Website: https://www.bainuomoulds.com/