C578 Type IX GPS
Additive grade
GPS = 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.
Values for the GPS condition
Other C578 Type IX grades and fills
C578 Type IX is listed in 4 conditions; see the grade overview at C578 Type IX.
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 | — |
GPSThis page 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 | — |
What is C578 Type IX GPS?
C578 Type IX GPS is C578 Type IX in the GPS grade — pick when the same 28.8 kg/m³ strength class must deliver 10–20 % lower thermal conductivity in a thinner build-up. C578 Type IX GPS has a tensile strength of 0.34 MPa (0.0493 ksi), weaker than 93% of polymer grades. The elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi). C578 Type IX GPS 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).
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 (0.0173 BTU/hr·ft·°F), worse than 96% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Absorbs moisture — dry before molding — 1.5%, worse than 91% of polymer grades
- Low stiffness — 0.01 GPa (8.7×10⁻⁴ Msi), worse than 86% of polymer grades
C578 Type IX GPS properties
Typical room-temperature values for C578 Type IX GPS; 17 are specific to this condition. Other listed values are C578 Type IX reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
C578 Type IX GPS 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 GPS has a tensile strength of 0.34 MPa (0.0493 ksi), weaker than 93% of polymer grades. The elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal8
C578 Type IX GPS is rated for continuous service to 75°C (167 °F). It conducts heat at 0.03 W/m·K (0.0173 BTU/hr·ft·°F), worse than 96% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
C578 Type IX GPS has an electrical resistivity of 1×10¹² Ω·m.
Chemical & Environmental2
UV resistance is poor.
Sustainability4
Producing a kilogram of C578 Type IX GPS 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 GPS's machinability is excellent (85/100, better than 88% of polymer grades); weldability poor (20/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C578 Type IX GPS
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.
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.
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) | — |
C578 Type IX GPS — frequently asked
What is C578 Type IX GPS used for?
C578 Type IX GPS 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 GPS?
C578 Type IX GPS has a typical tensile strength of 0.34 MPa (0.0493 ksi) — weaker than 93% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type IX GPS 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 GPS 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 GPS?
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 GPS 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 GPS?
C578 Type IX GPS 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.