EPS Foam Core
ASTM C578 · GB GB/T 10801.1
EPS Foam Core is bead-moulded expanded polystyrene classified to ASTM C578, from EPS-12 to EPS-45 plus graphite-loaded (EPS-GR) and flame-retardant (EPS-FR) types.
Reference datasheet — EPS Foam Core is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the EPS-22 condition
EPS Foam Core grades and fills
EPS Foam Core is supplied in 8 conditions, soft to hard. EPS-22 is the default FabDigit quotes; the values on this page are for it.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
EPS 12 kg/m³ | Cheapest, lightest grade — void fill, packaging and non-structural insulation only. | 0.13 | 2.5 | ||
EPS 15 kg/m³ | The commodity construction board; use where insulation matters more than load. | 0.17 | 3 | ||
Graphite-enhanced EPS | Choose when insulation value per thickness is critical — graphite IR blocker cuts λ ~15–20 % at equal density. | 0.2 | 3 | ||
EPS 18 kg/m³ | Common SIP and wall-panel core — best cost/strength balance in building use. | 0.21 | 3 | ||
Flame-retardant EPS | Mandatory grade for building envelopes and any panel that must meet GB 8624 B1/B2 or DIN 4102 B1. | 0.24 | 3 | ||
EPS-22Default EPS 22 kg/m³ | Default sandwich-panel core: enough shear strength for skin-bonded panels at still-low cost. | 0.25 | 3.5 | ||
EPS 29 kg/m³ | Pick when the core must carry real compressive/shear load — geofoam, floor and roof panels. | 0.35 | 4 | ||
EPS 38–48 kg/m³ | Highest-density EPS for hardpoints, tooling blocks, surfboard blanks and heavily loaded geofoam. | 0.48 | 4.5 |
What is EPS Foam Core?
EPS Foam Core is bead-moulded expanded polystyrene classified to ASTM C578, from EPS-12 to EPS-45 plus graphite-loaded (EPS-GR) and flame-retardant (EPS-FR) types. At 0.022 g/cm³ it gives 0.25 MPa tensile strength, 0.005 GPa modulus and 0.035 W/m·K conductivity, making it the cheapest filler for lightly loaded sandwich panels and SIP construction; it is supplied as moulded blocks, hot-wire-cut shapes and CNC-contoured cores. It is also the weakest and most solvent-sensitive core here: styrene in polyester and vinylester resins dissolves the beads and cut faces absorb water. XPS gives higher strength and lower moisture pickup at modest extra cost. EPS Foam Core has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 100% of composite grades. Its glass-transition temperature is 100°C (212 °F). EPS Foam Core has a tensile strength of 0.25 MPa (0.0363 ksi), weaker than 99% of composite grades. Elongation at break is 3.5% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
What is EPS Foam Core used for?
- structural insulated panels (SIPs)
- surfboard cores
- low-load architectural panels
- packaging sandwich structures
Advantages
- Lightweight — 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), better than 100% of composite grades
- Low embodied carbon — 3.3 kg CO₂/kg, better than 94% of composite grades
- Easy to machine — 85/100, better than 90% of composite grades
- Ductile — tolerates forming and impact — 3.5%, better than 78% of composite grades
Limitations
- Low stiffness — 0.01 GPa (7.25×10⁻⁴ Msi), worse than 100% of composite grades
- Hard to polish — 5/100, worse than 99% of composite grades
- Degrades in UV without stabilisers — 15/100, worse than 98% of composite grades
- Limited service temperature — 75°C (167 °F), worse than 96% of composite grades
- Poor heat conductor — 0.04 W/m·K (0.0202 BTU/hr·ft·°F), worse than 94% of composite grades
EPS Foam Core properties
Typical room-temperature values for EPS Foam Core-EPS-22; bars are the position among composite grades.
Physical4
EPS Foam Core has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 100% of composite grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical11
EPS Foam Core has a tensile strength of 0.25 MPa (0.0363 ksi), weaker than 99% of composite grades. Elongation at break is 3.5% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
Thermal8
EPS Foam Core is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0202 BTU/hr·ft·°F), worse than 94% of composite grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
EPS Foam Core has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is poor.
Sustainability4
Producing a kilogram of EPS Foam Core takes about 98 MJ of energy and emits 3.3 kg of CO₂ — less than 69% of composite grades. Typical recycled content is 5%.
Manufacturability3
EPS Foam Core's machinability is excellent (85/100, better than 90% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the composite family
Yield strength against density for every composite grade FabDigit runs. EPS Foam Core is highlighted; hover a dot for its name, or open the interactive family chart.
Working with EPS Foam Core
Is EPS Foam Core easy to machine?
Hot-wire cut or CNC route with sharp, fast, low-rake tools and vacuum extraction; avoid melt smearing and static bead scatter.
Can EPS Foam Core be welded?
Not weldable in the metal sense — blocks are joined by hot-plate/steam fusion, EPS-safe PU or water-based adhesives, or foam-safe spray glue.
Can EPS Foam Core be formed, bent or molded?
Pre-expand beads to target density, age 6–24 h, then steam-mould at ~0.8–1.1 bar (110–125 °C steam) or cut shapes from large moulded blocks; allow post-mould drying/stabilising.
EPS Foam Core chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| pentane (blowing agent, residual)highest as-expanded, decays with ageing | 0.1 – 6 | 1 |
| flame retardant (polymeric brominated, PFR grades only; HBCD phased out | 0 – 1 | 0.7 |
| graphite / carbon IR blockergrey/GPS grades only | 0 – 4 | 2 |
| nucleating & antistatic additives | 0 – 0.5 | 0.2 |
| polystyrene (styrene homopolymer)solid phase; foam is >95 vol % air | ≥ 92 (balance) |
What surface finishes work on EPS Foam Core?
Skin with FRP, cement board, metal or paper facings; only water-based or epoxy coatings — polyester/vinylester styrene and solvent paints dissolve the cells.
Equivalent designations
Standards and trade names that resolve to EPS Foam Core in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- C578
- GB (China)
- GB/T 10801.1
How much does EPS Foam Core cost?
EPS Foam Core is a standard-cost composite ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
EPS Foam Core — frequently asked
What is EPS Foam Core used for?
EPS Foam Core is typically used for structural insulated panels (SIPs), surfboard cores, low-load architectural panels and packaging sandwich structures. In short: cheapest sandwich core; lowest strength of the foams; epoxy or water-based adhesives only.
What is the tensile strength of EPS Foam Core?
EPS Foam Core has a typical tensile strength of 0.25 MPa (0.0363 ksi) — weaker than 99% of composite grades. Strength varies by condition: see the 8 listed tempers.
Is EPS Foam Core easy to machine?
Yes — machinability is rated excellent (85/100, better than 90% of composite grades). Hot-wire cut or CNC route with sharp, fast, low-rake tools and vacuum extraction; avoid melt smearing and static bead scatter.
Can EPS Foam Core be welded?
Not weldable in the metal sense — blocks are joined by hot-plate/steam fusion, EPS-safe PU or water-based adhesives, or foam-safe spray glue.
What surface finishes work on EPS Foam Core?
Skin with FRP, cement board, metal or paper facings; only water-based or epoxy coatings — polyester/vinylester styrene and solvent paints dissolve the cells.
Can EPS Foam Core be formed, bent or molded?
Pre-expand beads to target density, age 6–24 h, then steam-mould at ~0.8–1.1 bar (110–125 °C steam) or cut shapes from large moulded blocks; allow post-mould drying/stabilising.
What is the maximum service temperature of EPS Foam Core?
EPS Foam Core is rated for continuous use to about 75°C (167 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does EPS Foam Core cost?
EPS Foam Core is a standard-cost composite ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM C578 — Rigid Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- EN 13163 — Thermal insulation products: factory made EPS — CEN (2016)
- Cellular Solids: Structure and Properties (Gibson & Ashby) — Cambridge University Press (1997)
- Neopor / Styropor EPS technical data — BASF (2023)
- ICE Embodied Carbon Database v3 — EPS — Circular Ecology (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.