EPS FR (Flame-retardant EPS)
Flame-retardant grade
ASTM C578 · EN 13163 · GB GB/T 10801.1
Mandatory grade for building envelope insulation and any code-regulated construction use.
Values for the FR condition
Other EPS grades and fills
EPS is listed in 7 conditions; see the grade overview at EPS.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Ultra-light packaging foam, ~10 kg/m³ | Cheapest cushioning/void-fill foam where load-bearing and insulation demands are minimal. | 0.1 | 0.12 | 3.5 | |
Light insulation board, ~15 kg/m³ | Entry-level wall insulation and protective packaging where compressive load is light. | 0.15 | 0.18 | 3 | |
Graphite/IR-absorber modified grey EPS | Pick when the same thickness must deliver ~15–20 % lower lambda than white EPS. | 0.18 | 0.22 | 2.5 | |
EPS-20Default Standard insulation/packaging density, ~20 kg/m³ | The default balance of insulation value, strength and cost for EIFS boards and industrial packaging. | 0.2 | 0.25 | 3 | |
FRThis page Flame-retardant EPS | Mandatory grade for building envelope insulation and any code-regulated construction use. | 0.2 | 0.24 | 2.5 | |
High-density board, ~30 kg/m³ | Choose for under-slab, roof deck and geofoam-light duty where compressive load matters. | 0.3 | 0.36 | 2.5 | |
Structural/geofoam density, ~40 kg/m³ | Highest common EPS density for geofoam fill, load-bearing floors and heavy-duty packaging. | 0.4 | 0.47 | 2 |
What is EPS FR?
EPS FR is EPS in the FR grade — mandatory grade for building envelope insulation and any code-regulated construction use. EPS FR has a yield strength of 0.2 MPa (0.029 ksi) and a tensile strength of 0.24 MPa (0.0348 ksi) — weaker than 98% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi). EPS FR 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-20 is the default condition FabDigit quotes; FR is available on request or by drawing note.
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
- Low strength — 0.2 MPa (0.029 ksi), worse than 98% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0214 BTU/hr·ft·°F), worse than 91% of polymer grades
- Absorbs moisture — dry before molding — 1.5%, worse than 91% of polymer grades
- Low stiffness — 0.01 GPa (7.25×10⁻⁴ Msi), worse than 89% of polymer grades
EPS FR properties
Typical room-temperature values for EPS FR; 15 are specific to this condition. Other listed values are EPS reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
EPS FR 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).
Mechanical10
EPS FR has a yield strength of 0.2 MPa (0.029 ksi) and a tensile strength of 0.24 MPa (0.0348 ksi) — weaker than 98% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
Thermal9
EPS FR is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0214 BTU/hr·ft·°F), worse than 91% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
EPS FR has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), worse than 52% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of EPS FR 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 FR's machinability is excellent (90/100, better than 95% of polymer grades); weldability fair (45/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with EPS FR
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).
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.
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) |
EPS FR — frequently asked
What is EPS FR used for?
EPS FR 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 yield strength of EPS FR?
EPS FR has a typical yield strength of 0.2 MPa (0.029 ksi) and a tensile strength of 0.24 MPa (0.0348 ksi) — weaker than 98% of polymer grades. Strength varies by condition: see the 7 listed tempers.
Is EPS FR 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 FR 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 FR?
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 FR 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 FR?
EPS FR 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.
What is the difference between EPS-20 and EPS-40?
EPS-20 is the default condition — the default balance of insulation value, strength and cost for EIFS boards and industrial packaging. EPS-40: highest common EPS density for geofoam fill, load-bearing floors and heavy-duty packaging. Yield strength is 0.2 MPa in EPS-20 versus 0.4 MPa in EPS-40.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.