C578 Type IX
ASTM C578 Type IX is a higher-density molded EPS at roughly 28.8 kg/m³ (0.029 g/cm³), with a thermal conductivity of about 0.033 W/m·K and a service limit near 75 °C.
Reference datasheet — C578 Type IX 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.
C578 Type IX grades and fills
C578 Type IX is supplied in 4 conditions, soft to hard.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
EPS29 geofoam block to ASTM D6817 | Choose for lightweight embankment fill, bridge approach and retaining-wall backfill where elastic (1 % strain) resistance rather than 10 % strength governs. | — | 0.33 | 2.5 | — |
Graphite-enhanced (grey) high-density EPS | Pick when the same 28.8 kg/m³ strength class must deliver 10–20 % lower thermal conductivity in a thinner build-up. | — | 0.34 | 2.5 | — |
Borate/insect-resistant treated below-grade grade | Required by many codes for EPS in ground contact in termite-active regions (e.g. Perform Guard-type product). | — | 0.34 | 2.4 | — |
HBCD-free polymeric brominated flame retardant | Use where HBCD-free, REACH-compliant supply or a GB 8624 B1 classification with oxygen index of at least 30 is specified, at higher cost than legacy flame-retardant foam. | — | 0.35 | 2.5 | — |
Supply forms, finishes and certifications
Ways C578 Type IX is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FACED | Laminated with poly film, foil or coated kraft facer | Coating |
STDDefault | Standard white block-molded Type IX board, unfaced | Standard supply |
What is C578 Type IX?
ASTM C578 Type IX is a higher-density molded EPS at roughly 28.8 kg/m³ (0.029 g/cm³), with a thermal conductivity of about 0.033 W/m·K and a service limit near 75 °C. Its higher compressive strength is why engineers choose it for bearing under-slab insulation and road embankment fill; it is supplied as molded block, sliced board, geofoam blocks and shape-molded parts, including FR-polymer and borate-treated variants. Cost per board rises with density, and the foam is still solvent-, bitumen- and UV-sensitive. Use XPS where long-term water immersion is expected. C578 Type IX has a density of 0.03 g/cm³ (0.001 lb/in³), lighter than 95% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type IX has a tensile strength of 0.35 MPa (0.0508 ksi), weaker than 92% of polymer grades. The elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
What is C578 Type IX used for?
- Roadway embankment fill
- Load-bearing under-slab insulation
- Cold storage floors
Advantages
- Lightweight — 0.03 g/cm³ (0.001 lb/in³), better than 95% of polymer grades
- Easy to machine — 85/100, better than 88% of polymer grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 76% of polymer grades
Limitations
- Poor heat conductor — 0.03 W/m·K (0.0191 BTU/hr·ft·°F), worse than 95% of polymer grades
- Absorbs moisture — dry before molding — 1.5%, worse than 91% of polymer grades
- Degrades in UV without stabilisers — 20/100, worse than 88% of polymer grades
- Low stiffness — 0.01 GPa (8.7×10⁻⁴ Msi), worse than 86% of polymer grades
C578 Type IX properties
Typical room-temperature values; bars are the position among polymer grades.
Physical4
C578 Type IX has a density of 0.03 g/cm³ (0.001 lb/in³), lighter than 95% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical8
C578 Type IX has a tensile strength of 0.35 MPa (0.0508 ksi), weaker than 92% of polymer grades. The elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal8
C578 Type IX is rated for continuous service to 75°C (167 °F). It conducts heat at 0.03 W/m·K (0.0191 BTU/hr·ft·°F), worse than 95% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
C578 Type IX has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
UV resistance is poor.
Sustainability4
Producing a kilogram of C578 Type IX takes about 100 MJ of energy and emits 3.4 kg of CO₂ — less than 61% of polymer grades. Typical recycled content is 5%.
Manufacturability4
C578 Type IX's machinability is excellent (85/100, better than 88% of polymer grades); weldability poor (20/100); formability fair (45/100).
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 polymer family
Yield strength against density for every polymer grade FabDigit runs. C578 Type IX is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type IX
Is C578 Type IX easy to machine?
Cut with hot wire, band saw or CNC router; avoid melting smear by keeping wire temperature low and use vacuum extraction for bead dust.
Can C578 Type IX be welded?
Not welded in practice — bond with water-based or EPS-compatible construction adhesive, foam-safe polyurethane, or mechanically fasten with plates/washers; solvent adhesives destroy the foam.
Can C578 Type IX be formed, bent or molded?
Produced by pre-expansion of pentane-blown beads, aging, then block molding under steam and hot-wire slicing; allow post-mold aging to stabilize dimensions before cutting to tolerance.
C578 Type IX 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 (residual blowing agent)decays after aging/curing | 0.2 – 2 | 1 |
| flame retardant (polymeric brominated / needed to meet LOI ≥ 24 % | 0.3 – 1.5 | 0.8 |
| graphiteGPS (grey EPS) variant only | 0 – 4 | 0 |
| nucleating/processing additives | 0 – 0.5 | 0.2 |
| polystyrene (styrene homopolymer)expanded bead matrix; foam is ~96–97 vol % air | ≥ 95 (balance) | — |
What surface finishes work on C578 Type IX?
Face with cement board, stucco/EIFS base coat, foil or film laminates; protect permanently from UV and from solvent-based coatings, and provide a code-required thermal barrier in interior use.
How much does C578 Type IX cost?
C578 Type IX is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C578 Type IX — frequently asked
What is C578 Type IX used for?
C578 Type IX is typically used for roadway embankment fill, load-bearing under-slab insulation and cold storage floors. In short: highest-density common EPS; load-bearing EPS grade; structural geofoam fill.
What is the tensile strength of C578 Type IX?
C578 Type IX has a typical tensile strength of 0.35 MPa (0.0508 ksi) — weaker than 92% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type IX easy to machine?
Yes — machinability is rated excellent (85/100, better than 88% of polymer grades). Cut with hot wire, band saw or CNC router; avoid melting smear by keeping wire temperature low and use vacuum extraction for bead dust.
Can C578 Type IX be welded?
Not readily — weldability is rated poor (20/100). Not welded in practice — bond with water-based or EPS-compatible construction adhesive, foam-safe polyurethane, or mechanically fasten with plates/washers; solvent adhesives destroy the foam.
What surface finishes work on C578 Type IX?
Face with cement board, stucco/EIFS base coat, foil or film laminates; protect permanently from UV and from solvent-based coatings, and provide a code-required thermal barrier in interior use.
Can C578 Type IX be formed, bent or molded?
Produced by pre-expansion of pentane-blown beads, aging, then block molding under steam and hot-wire slicing; allow post-mold aging to stabilize dimensions before cutting to tolerance.
What is the maximum service temperature of C578 Type IX?
C578 Type IX is rated for continuous use to about 75°C (167 °F), and briefly to 95°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type IX cost?
C578 Type IX is a standard-cost polymer ($$), 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 C578-22 Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- ASTM D6817 Standard Specification for Rigid Cellular Polystyrene Geofoam — ASTM International (2021)
- Type IX / 25 psi EPS insulation board technical data — Insulfoam / Foam-Control (ACH Foam) (2023)
- EPS physical property and compatibility bulletins — EPS Industry Alliance (2022)
- Materials and the Environment / CES eco-property data (EPS foam) — Ashby / Granta (2021)
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.