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Foams

Foams are polymers expanded with gas into open- or closed-cell structures at densities of roughly 10–500 kg/m³, a few percent of the solid. Polyurethane foams cover cushioning, comfort and molded skins; EVA Foam, EPE and POE Foam are the closed-cell packaging and padding grades; EPP Foam and EPS are the molded bead foams for crash protection and packaging; XPS and Phenolic Foam boards insulate; Poron is the microcellular urethane for gaskets and shock pads. The base polymer sets temperature and chemical resistance, but density and cell structure decide nearly everything else.

Popular foam grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityBest for
EVA Foam110.06ExcellentDie-cut inserts, padding, case liners
PU Foam000.03ExcellentCushioning, packaging, molded seating
EPP Foam010.05GoodMolded reusable crash and returnable packaging
Poron110.32Very goodThin precise gaskets and shock pads, no set
EPS000.02ExcellentOne-way protective packaging and insulation
XPS000.03ExcellentRigid insulation boards and model bases
EPDM Foam—10.1ExcellentWeather-stripping and outdoor closed-cell seals

All 60 foam grades

Choose foams for

Packaging inserts and case liners (EVA Foam, EPE, EPP Foam, EPS); seat, armrest and grip cushioning (PU Foam, Viscoelastic PU Foam, Integral Skin PU Foam); thin gaskets, dust seals and shock pads inside enclosures (Poron, EPDM Foam, Silicone Foam (Sponge Rubber)); rigid insulation and lightweight model or pattern boards (XPS, Phenolic Foam); sandwich-panel cores (PMI Foam, PVC Foam (Rigid, Structural Core), Syntactic Foam (Epoxy)); and acoustic or vibration-isolation pads.

Look elsewhere when

The part must carry a defined static load without creeping (a solid elastomer or rigid plastic), it needs a sealed, precise dimension (foam tolerances are ±0.5 mm at best and compress under fixturing), the temperature exceeds about 100 °C for PU and EVA (Silicone Foam (Sponge Rubber) and Melamine Foam reach 150–200 °C; beyond that mineral wool or ceramic fiber), or the foam is exposed to fuel, oil or solvents that swell the base polymer — check the polymer, not the foam.

Tensile strength against max service temp, Foams among every polymer grade

No materials in view have both of these properties.

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Foam by application

Protective packaging
EPE and PE Foam Board for repeated-drop cushioning of lighter goods; EPS for one-way shipping of heavy items at the lowest cost; EPP Foam when the packaging is returnable and must survive hundreds of impacts; EVA Foam for die-cut, laminated case inserts where appearance matters.
Gaskets and seals in enclosures
Poron (microcellular PU, 0.5–6 mm sheet) for dust and light seals that recover after years of compression; EPDM Foam and Silicone Foam (Sponge Rubber) closed-cell for weather and temperature; PVC Foam (Flexible, Closed-Cell) tape for low-cost sealing strips.
Cushioning and comfort
PU Foam at 20–60 kg/m³ for seats and padding; HR Foam for durable seating; Viscoelastic PU Foam for pressure-distributing pads and helmets; Integral Skin PU Foam and RIM PU Foam for molded armrests, grips and steering wheels with a tough skin.
Structural cores and insulation
PMI Foam for aerospace sandwich cores cured at high temperature; PVC Foam (Rigid, Structural Core) for marine and transport panels; Syntactic Foam (Epoxy) for deep-water buoyancy; XPS and Phenolic Foam for thermal insulation boards.

Working with foam

Cutting and machining
Sheet foams (EVA Foam, Poron, PE Foam Board, EPDM Foam) die-cut, kiss-cut, waterjet and CNC-knife cut cleanly to about ±0.5 mm; XPS, EPS and rigid PU boards CNC-route and hot-wire cut for patterns and packaging. Soft open-cell PU Foam is contour-cut with a bandsaw or wire and cannot hold tight tolerances. Skive thick blocks into sheets rather than machining thin sections.
Molding
EPP Foam and EPS are steam-chest molded from expanded beads in steel or aluminum tools — good for 1,000-plus identical inserts, uneconomic below a few hundred. PU foams are poured or RIM-injected into heated aluminum or epoxy molds and self-skin; EVA Foam is compression-molded and cross-linked. Specify density (kg/m³) with the compression stress or deflection at 25 % and 50 % (ISO 3386, ASTM D3574).
Bonding and lamination
PU and EVA foams laminate with spray contact adhesive, hot-melt or pressure-sensitive adhesive (most Poron and EVA Foam sheet is supplied with PSA on one side); EPP Foam and EPE are hard to glue and are hot-plate or hot-air welded or mechanically nested. Solvent-based adhesives dissolve EPS and XPS — use water-based or hot-melt.
Specifying and regulatory
State density, cell type (open or closed), hardness (ILD or CFD), compression set and, where it matters, flame rating: UL 94 HF-1 and FMVSS 302 for enclosures and vehicles, ASTM C578 types for insulation boards. Most PU foams yellow in light and degrade in UV; EPDM Foam and Silicone Foam (Sponge Rubber) last outdoors. Open-cell foams absorb water; closed-cell foams float and seal.

Other polymer series

Foams — frequently asked

What is foam?

Foams are polymers expanded with gas into open- or closed-cell structures at densities of roughly 10–500 kg/m³, a few percent of the solid. Polyurethane foams cover cushioning, comfort and molded skins; EVA Foam, EPE and POE Foam are the closed-cell packaging and padding grades; EPP Foam and EPS are the molded bead foams for crash protection and packaging; XPS and Phenolic Foam boards insulate; Poron is the microcellular urethane for gaskets and shock pads. The base polymer sets temperature and chemical resistance, but density and cell structure decide nearly everything else.

Which grade of foam should I use?

PU Foam is the general answer — flexible open-cell for cushioning and packaging, Viscoelastic PU Foam for memory-foam comfort, Rebond Foam for dense pads, Semi-Rigid PU Foam and Integral Skin PU Foam for molded armrests and steering wheels, rigid polyurethane boards for insulation and tooling patterns. Poron for thin, precise die-cut gaskets, shock pads and enclosure seals that must not take a compression set. EVA Foam for die-cut inserts, padding, footwear and case liners; EPE and PE Foam Board for cushioning packaging; EPP Foam for molded, reusable crash and returnable packaging; EPS for one-way protective packaging and insulation; XPS for rigid insulation and model bases; Melamine Foam for acoustic and high-temperature duty; PMI Foam and PVC Foam (Rigid, Structural Core) as sandwich-panel cores.

Which grade of foam is the strongest?

PC-Foam has the highest yield strength in the series at 43 MPa; RIM PU Foam follows at 8 MPa. Values are for each grade's default condition.

Which grade of foam is easiest to machine?

C578 Type II (machinability excellent, 95/100), then EPS 100 (95/100).

EVA foam or polyurethane foam for a case insert?

EVA Foam is closed-cell, water-resistant, takes a clean die-cut or CNC-routed edge and looks finished — the choice for tool cases, instrument inserts and anything the customer sees. PU Foam (open-cell, or Reticulated PU Foam) is softer, cheaper in thick blocks and cushions light, delicate items better, but tears more easily, absorbs water and yellows. Use EVA Foam for the visible cavity layer and PU Foam or EPE beneath it for the cushioning depth.

What density should I specify?

It depends on the job: 20–35 kg/m³ for PU seating and packaging cushions, 45–60 kg/m³ for EVA case inserts and mats, 20–60 kg/m³ for EPP crash and returnable packaging (higher for repeated impacts), 15–30 kg/m³ for EPS and XPS insulation and one-way packaging, and 240–480 kg/m³ for Poron gasket sheet. Add the compression stress at 25 % deflection and the compression set at the service temperature — two foams at the same density can differ by 3 × in firmness.