Polymer
EPS
Properties, grades, machining, finishes and uses — values shown for the EPS-20 condition.
EPS is bead-foamed, closed-cell expanded polystyrene supplied to C578, EN 13163 and GB/T 10801.1, in density classes EPS-10 through EPS-40 plus graphite-loaded (GEPS), flame-retardant, food-contact and antistatic variants.
Reference datasheet — EPS 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.
What is EPS?
EPS is bead-foamed, closed-cell expanded polystyrene supplied to C578, EN 13163 and GB/T 10801.1, in density classes EPS-10 through EPS-40 plus graphite-loaded (GEPS), flame-retardant, food-contact and antistatic variants. Engineers specify it for the lowest cost per unit of thermal resistance: the default grade is 0.02 g/cm³ with 0.036 W/m·K conductivity, 0.25 MPa tensile strength and a 0.005 GPa modulus, and it is sold as molded block, cut board and shape-molded packaging. Limits are the 75 °C service ceiling, very low mechanical strength, higher water uptake than extruded board, and no solvent or UV resistance. XPS is the nearest alternative where compressive strength and wet-service performance matter. EPS has a density of 0.02 g/cm³ (7.23×10⁻⁴ lb/in³), lighter than 98% of polymer grades. Its glass-transition temperature is 100°C (212 °F). EPS has a tensile strength of 0.25 MPa (0.0363 ksi), weaker than 95% of polymer grades. The elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
What is EPS used for?
- Building insulation board
- Protective packaging
- Disposable coolers
- Void fill
- Lightweight concrete fill
Advantages
- Lightweight — 0.02 g/cm³ (7.23×10⁻⁴ lb/in³), better than 98% of polymer grades
- Easy to machine — 90/100, better than 95% of polymer grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 76% of polymer grades
Limitations
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades
- Absorbs moisture — dry before molding — 1.5%, worse than 92% of polymer grades
- Low stiffness — 0.01 GPa (7.25×10⁻⁴ Msi), worse than 89% of polymer grades
EPS properties
Typical room-temperature values for EPS-EPS-20 (the default balance of insulation value, strength and cost for eifs boards and industrial packaging), compiled from standards, handbooks and producer data. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher. Other conditions have their own pages: see tempers.
Physical4
EPS has a density of 0.02 g/cm³ (7.23×10⁻⁴ lb/in³), lighter than 98% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical7
EPS has a tensile strength of 0.25 MPa (0.0363 ksi), weaker than 95% of polymer grades. The elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
Thermal8
EPS is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
EPS has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), worse than 55% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of EPS takes about 105 MJ of energy and emits 3.4 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability5
EPS's machinability is excellent (90/100, better than 95% of polymer grades); weldability fair (45/100); formability very good (70/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
EPS grades and fills
EPS is supplied in 9 conditions, each with its own property set. Open one for its full datasheet. EPS-20 is what FabDigit quotes unless the drawing says otherwise.
- EPS-20DefaultThe default balance of insulation value, strength and cost for EIFS boards and industrial packaging.0.25 MPa tensile
- EPS-40Highest common EPS density for geofoam fill, load-bearing floors and heavy-duty packaging.0.47 MPa tensile
- EPS-30Choose for under-slab, roof deck and geofoam-light duty where compressive load matters.0.36 MPa tensile
- EPS-15Entry-level wall insulation and protective packaging where compressive load is light.0.18 MPa tensile
- EPS-10Cheapest cushioning/void-fill foam where load-bearing and insulation demands are minimal.0.12 MPa tensile
4 further conditions are listed below with a summary only.
| Condition | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
EPS-20Default standard insulation/packaging density, ~20 kg/m³ (ASTM C578 Type II) | The default balance of insulation value, strength and cost for EIFS boards and industrial packaging. | — | 0.25 | — | — | 0.04 W/m·K |
ultra-light packaging foam, ~10 kg/m³ | Cheapest cushioning/void-fill foam where load-bearing and insulation demands are minimal. | — | 0.12 | — | — | 0.04 W/m·K |
light insulation board, ~15 kg/m³ (ASTM C578 Type I) | Entry-level wall insulation and protective packaging where compressive load is light. | — | 0.18 | — | — | 0.04 W/m·K |
high-density board, ~30 kg/m³ (ASTM C578 Type IX) | Choose for under-slab, roof deck and geofoam-light duty where compressive load matters. | — | 0.36 | — | — | 0.03 W/m·K |
structural/geofoam density, ~40 kg/m³ (ASTM C578 Type XV) | Highest common EPS density for geofoam fill, load-bearing floors and heavy-duty packaging. | — | 0.47 | — | — | 0.03 W/m·K |
graphite/IR-absorber modified grey EPS (Neopor type) | Pick when the same thickness must deliver ~15–20 % lower lambda than white EPS. | — | 0.22 | — | — | 0.03 W/m·K |
flame-retardant EPS (polymeric brominated FR, GB 8624 B1/B2) | Mandatory grade for building envelope insulation and any code-regulated construction use. | — | — | — | — | 0.04 W/m·K |
food-contact / low-residual-monomer molded EPS | Use for fish/produce boxes, cups and lunch boxes needing FDA 21 CFR 177.1640 or GB 4806.6 compliance. | — | — | — | — | 0.04 W/m·K |
antistatic EPS (pink/blue, surface-treated) for electronics packaging | Select for ESD-sensitive electronics cushioning where charge generation must be limited. | — | — | — | — | 0.04 W/m·K |
Working with EPS
Is EPS easy to machine?
Hot-wire cutting or CNC hot-wire/router with sharp tools and vacuum extraction; avoid friction heat and use light passes to prevent bead pull-out.
Can EPS be welded?
Not fusion-weldable in the plastics-welding sense — blocks are joined by steam fusion during molding, or bonded with water-based/hot-melt adhesives (never solvent adhesives).
Can EPS be formed, bent or molded?
Pre-expand beads with steam, age 6–24 h, then block or shape mold at 0.6–1.2 bar steam and 100–120 °C; allow post-mold drying/aging to stabilize dimensions (0.3–0.8 % shrinkage).
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. EPS is highlighted; hover a dot for its name, or open the interactive family chart.
EPS 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 (n-/iso-pentane blowing agent)in raw bead; <0.5 % residual in aged product | 3 – 7 | 5 |
| flame retardant (polymeric brominated, PFR grades only; HBCD phased out | 0.4 – 1.2 | 0.8 |
| nucleating agent / wax, coating (zinc stcell-size and mold-release additives | 0.1 – 1 | 0.4 |
| graphite / carbon IR absorbergrey GEPS variants only | 0.5 – 4 | 2 |
| polystyrene (styrene homopolymer)Mw ≈ 180,000–260,000 | ≥ 90 (balance) | — |
What surface finishes work on EPS?
Coat with cement or acrylic skim coats, water-based paints or laminate facings; solvent paints, PU foam and hot bitumen (>90 °C) will attack the surface, and UV exposure demands prompt covering.
Equivalent designations
Standards and trade names that resolve to EPS in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- C578
- EN / DIN / Werkstoff-Nr.
- 13163
- GB (China)
- GB/T 10801.1
- Also called
- EPS
How much does EPS cost?
EPS is a budget-cost polymer ($), cheaper than about 91% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
EPS — frequently asked
What is EPS used for?
EPS is typically used for building insulation board, protective packaging, disposable coolers, void fill and lightweight concrete fill. In short: lowest-cost rigid insulation foam; lightest styrenic foam; best cost per R-value.
What is the tensile strength of EPS?
EPS has a typical tensile strength of 0.25 MPa (0.0363 ksi) — weaker than 95% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is EPS easy to machine?
Yes — machinability is rated excellent (90/100, better than 95% of polymer grades). Hot-wire cutting or CNC hot-wire/router with sharp tools and vacuum extraction; avoid friction heat and use light passes to prevent bead pull-out.
Can EPS be welded?
With care — weldability is rated fair (45/100). Not fusion-weldable in the plastics-welding sense — blocks are joined by steam fusion during molding, or bonded with water-based/hot-melt adhesives (never solvent adhesives).
What surface finishes work on EPS?
Coat with cement or acrylic skim coats, water-based paints or laminate facings; solvent paints, PU foam and hot bitumen (>90 °C) will attack the surface, and UV exposure demands prompt covering.
Can EPS be formed, bent or molded?
Pre-expand beads with steam, age 6–24 h, then block or shape mold at 0.6–1.2 bar steam and 100–120 °C; allow post-mold drying/aging to stabilize dimensions (0.3–0.8 % shrinkage).
What is the maximum service temperature of EPS?
EPS is rated for continuous use to about 75°C (167 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does EPS cost?
EPS is a budget-cost polymer ($), cheaper than about 91% 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)
- Styropor / Neopor EPS technical information — BASF (2021)
- Engineered Materials Handbook Vol.2: Engineering Plastics — ASM International (1988)
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.