The short answer to EPP vs EPS foam: EPP when the part is struck more than once, has to come back, or works above 75 °C. EPS when it ships once, insulates, and has to be cheap.
DBM molds both on the same machines. Figures are typical ranges, not guaranteed limits: your part depends on geometry, wall thickness and as-molded density. We confirm final values in writing before tooling.
Both are closed-cell bead foams molded in a steam chest, both recyclable. The difference is the second impact: EPP, a polypropylene bead, deforms and comes back; EPS, a polystyrene bead, crushes once and stays crushed.
The EPP and EPS columns of the thirteen-material dataset behind our comparison tool. Wide ranges are density windows.
| Property | EPP | EPS | What the gap means for your part |
|---|---|---|---|
| Molded density (kg/m³) | 20–66 | 15–60 | EPS reaches lower at the light end: 15 kg/m³ for volume packaging and insulation, where the lightest EPP we mold is 20. EPP reaches higher at the heavy end, 66 kg/m³ against 60. Between 20 and 60 kg/m³ the two windows overlap almost completely, so density on its own rarely decides the material. |
| Compression stress at 10% strain (kPa) | 50–325 | 60–430 | At equal density EPS is the stiffer material, and at the top of its density window it still carries more, 430 kPa against 325 kPa, but the margin is narrow. EPP wins on load per kilogram, not on peak load, which is exactly why the density you pick is a cost decision, not a habit. |
| Energy return / rebound (%) | 30 | 5–15 | The row that decides reuse. EPP returns around 30% of the impact energy, two to six times what EPS gives back, and comes back to shape afterwards; EPS turns the rest into permanent deformation and stays dented. |
| Long-term service temperature (°C) | 100 | 75 | A sealed container on a summer quay reaches 70 °C without difficulty. That is the margin EPS does not have and EPP does. |
| Minimum service temperature (°C) | −40 | −50 | The one temperature contest EPS wins, and now only by 10 °C. Deep-frozen logistics below −40 °C is an EPS or Beaded EPE conversation, not an EPP one. |
| Thermal conductivity, W/(m·K) | 0.036–0.042 | 0.032–0.037 | EPS insulates noticeably better at the same thickness. On a cold-chain shipper that difference is hours of holdover time, so insulation-led parts default to EPS. |
| Feel and rigidity | Semi-rigid: cushions under load, not under a finger | Hard and brittle, almost no elastic deformation | Press both with a thumb and neither moves. Drop both and only EPP is still the right shape afterwards. |
| Flame behaviour | GB 8410 ≤70–90 mm/min | No flame rating held; can be modified to reach one | EPP is published with a horizontal burn rate against the automotive interior method; flame-retardant EPP grades are available across the density range. EPS carries no rating as we mold it and would have to be modified to hold one. |
| Chemical resistance | Polyolefin base: good with acid, alkali, alcohols; not aromatics or chlorinated solvents | Only 4 of 13 tested media resisted | Solvent contact, adhesives, cleaning agents and fuel vapour all point to EPP. EPS dissolves in far too many workshop liquids to be trusted near them. |
| Weather resistance | PP tertiary hydrogen triggers photo-oxidation; chalks outdoors within months without additives | Benzene rings absorb UV strongly, so it yellows, chalks and cracks; among the worst outdoors | Neither is an outdoor material as supplied. EPP is the one worth stabilising, because UV additives and carbon black can lift it and it has the mechanical life to justify the effort. |
| End of life | Thermoplastic, re-pelletisable, no cross-linking | Thermoplastic and recyclable; mature collection but often limited by contamination | Both are single-polymer and both can be re-pelletised. The practical difference is that an EPP part is usually reused before it is ever recycled, which is the larger saving. |
Same dataset, all thirteen materials
EPP returns about 30% of absorbed energy and recovers over 95% of its compressed thickness. EPS returns 5–15% and keeps the dent. For a part that is hit once, either works and EPS costs less. For a part that is hit again, EPS is finished after the first drop. A returnable tray with EPS liners has a permanent hole; with EPP liners it still cushions.
On one journey, resilience is capacity you pay for and never use. EPS is the cost and insulation baseline: cheaper beads, faster cycles, lower density for the same stiffness. Ask whether the foam comes back. If it does not, start at EPS.
EPP runs continuously to 100 °C, short-term to 120 °C, down to −40 °C. EPS is a 75 °C material and no grade closes the gap. That ceiling is crossed more often than people expect: a sealed container in the tropics, a hot-fill product loaded warm. EPS wins the cold end, to −50 °C.
Thermal conductivity is 0.032–0.037 W/(m·K) against 0.036–0.042 W/(m·K). On a cold-chain shipper that is hours of holdover. If the spec leads with a temperature-hold requirement rather than a drop test, EPS is the default. Where handling is rough too, we mold an EPS shell with EPP corners.
At equal density EPS is stiffer: our 20, 25 and 30 kg/m³ EPS grades give 90–160 kPa at 10% strain, EPP at 20–25 kg/m³ gives 50–70 kPa. EPP buys capacity with density, reaching 255–325 kPa at 54–66 kg/m³. Specify the load and the deflection you accept and let the grade follow: a step up is often 30–50% more polymer.
EPS resisted only 4 of the 13 media in our chemical panel. EPP, a polyolefin, handles acids, alkalis and alcohols and gives up only against aromatics and chlorinated solvents. Near solvent adhesives, fuels, line cleaners or plasticised PVC, EPS is a liability.
We publish EPP burn rates against GB 8410, the automotive interior horizontal burn method: ≤70 mm/min at 54–66 kg/m³, ≤80 at 40–50 kg/m³, ≤90 at 27–33 kg/m³. Flame-retardant grades run across the density range; EPS as we mold it holds no rating. The caveat: a burn rate is not a vertical-burn classification. Tell us your standard; we will confirm what the grade holds.
Ten application families, the material we start from, and why.
| Application | Start from | Typical density | Why |
|---|---|---|---|
| Single-trip protective packaging | EPS | 20–30 kg/m³ | One drop event, cost-led, recycled at destination. Resilience would be paid for and never used. |
| Returnable dunnage and KLT inserts | EPP | 27–50 kg/m³ | Dozens to hundreds of trips. Recovery after impact and dimensional stability are the whole specification. |
| Cold-chain shippers and insulated boxes | EPS | 20–25 kg/m³ | Lowest conductivity of the two, and the payload rarely comes back. Add EPP corners only where handling is rough. |
| Appliance and HVAC internals | EPP | 27–50 kg/m³ | Air paths and ducting run warm, assembly is automated, and parts must not shed beads into the machine. |
| Automotive energy absorption | EPP | 40–66 kg/m³ | Cabin temperatures, a burn-rate specification, and a bumper core that must still be intact after a low-speed event. |
| Battery module trays and ESS packaging | EPP | 40–66 kg/m³ | Load-bearing, returnable, and normally required to hold a flame specification. Flame-retardant EPP grades exist for exactly this. |
| Helmet liners and sports padding | EPS single-impact · EPP multi-impact | 30–66 kg/m³ | A certified single-impact helmet liner is an EPS part by design. Training, recreational and repeat-use padding is EPP. |
| Drone and UAV airframes | EPO, then EPP | 16–33 kg/m³ | Neither. EPO gives PS stiffness with PE toughness at the lowest density we mold; EPP is the tougher, heavier fallback. |
| Building void fill and insulation board | EPS | 20–30 kg/m³ | Insulation-led, cost-led, no impact duty. Nothing about the application asks for what EPP costs more to provide. |
| Precision instrument and optics cases | EPP | 40–66 kg/m³ | Reusable, low bead shed, tolerant of cleaning agents, and stable enough to keep locating a heavy payload accurately. |
Both are families of density grades, and the grade decides the part more than the polymer. EPP compression is at 10% strain to ISO 844, EPS as minimum guaranteed values to GB/T 8813.
| Density grade | Material | Density (kg/m³) | Compression at 10% strain (kPa) | Where it belongs |
|---|---|---|---|---|
| 54–66 kg/m³ | EPP | 54–66 | 255–325 | Structural and load-bearing parts. The stiffest grade in this table. |
| 40–50 kg/m³ | EPP | 40–50 | 130–175 | Structural cushioning: automotive, handling trays, heavier returnable packaging. |
| 27–33 kg/m³ | EPP | 27–33 | 70–100 | Protective packaging and lightweight parts with strong energy absorption. |
| 20–25 kg/m³ | EPP | 20–25 | 50–70 | Ultra-light cushioning, insulation and dunnage where weight is the constraint. |
| 20 kg/m³ | EPS | 20 | ≥90 | Volume protective packaging and insulation. The cost baseline of the whole comparison. |
| 25 kg/m³ | EPS | 25 | ≥120 | Heavier payloads and boxes that need more edge strength than 20 kg/m³ gives. |
| 30 kg/m³ | EPS | 30 | ≥160 | The stiff end of our standard EPS grades: dense enough to compete with mid-density EPP on load, but not on recovery. |
Both materials run in the same steam chest, so tooling is priced off the part: envelope, geometry, cavity count, service life. Switching material later need not mean a new tool. Shrinkage differs, though, and a tool cut for one is rarely perfect in the other.
Running cost does change: EPP beads cost more per kilogram, the cycle is longer, and EPP parts are molded denser. An EPP part that makes fifty trips competes with fifty EPS parts.
If the pair above is not yours, one of these is.
| Comparison | The decision it settles |
|---|---|
| EVA vs EPP foam | Soft conforming contact against structural load. Whether the foam touches a surface or carries it. |
| EPP vs ETPU foam | Elastomer resilience at around 200 kg/m³ against all-round cushioning at 30. What the extra polymer mass actually buys. |
| EPP vs Beaded EPE foam | Rigidity and repeated impact against soft wrap, surface safety and service down to −70 °C. |
| EPP vs EPO foam | Where a PS/polyolefin composite bead at 16 kg/m³ is better value than either EPS or EPP. |
| All thirteen, ranked | Every material sorted on each of the seven properties that settle a spec. |
| EPE vs Beaded EPE foam | The same polyethylene shaped two ways: what the forming route costs and buys. |
| Cut vs molded foam | Which forming process the part needs: shape freedom and seams against tooling commitment. |
Recovery. EPP returns around 30% of the energy it absorbs and springs back to shape after impact, so it can be hit repeatedly and reused. EPS returns only 5–15% and stays permanently deformed, which makes it a single-impact material. Every other practical difference follows from this: EPP for returnable and multi-impact parts, EPS for single-trip packaging and insulation.
Not at the same density. At 20–30 kg/m³ EPS delivers 90–160 kPa at 10% strain, comparable to or better than EPP at the same weight. EPP is stronger across the grades we stock, because it is available denser: our 54–66 kg/m³ grade reaches 255–325 kPa, beyond anything our standard EPS grades offer. Specify the load and the deflection you can accept, and let the density grade follow from that rather than choosing the polymer first.
EPS. Its thermal conductivity is 0.032–0.037 W/(m·K) against 0.036–0.042 W/(m·K) for EPP, so at equal wall thickness an EPS box holds temperature longer. For cold-chain shippers and insulated boxes that difference runs to hours of holdover, which is why insulation-led parts start from EPS even when the handling case would favour EPP.
EPP is published for continuous service to 100 °C with short-term excursions to 120 °C, and down to −40 °C. EPS is a 75 °C material at the top end but goes lower at the bottom, staying serviceable to around −50 °C. So EPP wins the heat case (sealed containers, engine bays, appliances), and EPS wins the deep-freeze case.
Per part, yes: the beads cost more per kilogram, the cycle is longer, and EPP parts are usually molded denser. Per use, often not. An EPP dunnage insert that completes fifty trips is competing against fifty EPS parts plus fifty disposals, and it wins that comparison comfortably. Tooling cost is close to identical because both materials are molded in the same steam-chest tool.
Both are single-polymer thermoplastics with no cross-linking, so both can be re-pelletised and re-used as raw material. EPS has the more mature collection infrastructure but suffers more from contamination in practice. The larger environmental difference is upstream: an EPP part is usually reused many times before it ever reaches a recycling stream.
You do not have to name a material. Tell us what the part has to survive: the drop, the temperature, the trips. We come back with a material, a grade and a sample plan within 48 hours.