C578 Type II GPS
Additive grade
GPS = graphite-enhanced grey EPS at same density
Choose when the same board thickness must deliver ~15–20 % lower thermal conductivity; graphite IR blocker, but more sun-sensitive during installation.
Values for the GPS condition
Other C578 Type II grades and fills
C578 Type II is listed in 4 conditions; see the grade overview at C578 Type II.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
GPSThis page Graphite-enhanced grey EPS at same density | Choose when the same board thickness must deliver ~15–20 % lower thermal conductivity; graphite IR blocker, but more sun-sensitive during installation. | — | 0.22 | 4 | — |
Geofoam EPS22 | Same ~22 kg/m³ density supplied as large sawn blocks to ASTM D6817 for embankment, backfill and void-form applications where creep-limited 1 % strain stress governs. | — | 0.23 | 5 | — |
FRDefault Flame-retardant building grade | Default construction board: contains polymeric brominated FR, meets ASTM C578 §11 / GB 8624 B1–B2 requirements for wall and roof insulation. | — | 0.24 | 5 | — |
Packaging / non-building grade | Same density and mechanicals without flame retardant — cheaper, for packaging, void fill and non-regulated uses only. | — | 0.25 | 5 | — |
What is C578 Type II GPS?
C578 Type II GPS is C578 Type II in the GPS grade — choose when the same board thickness must deliver ~15–20 % lower thermal conductivity; graphite IR blocker, but more sun-sensitive during installation. C578 Type II GPS has a tensile strength of 0.22 MPa (0.0319 ksi), weaker than 96% of polymer grades. Elongation at break is 4% and the elastic modulus is 0 GPa (6.67×10⁻⁴ Msi). C578 Type II GPS has a density of 0.02 g/cm³ (7.8×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F). FR is the default condition FabDigit quotes; GPS is available on request or by drawing note.
Advantages
- Easy to machine — 95/100, better than 100% of polymer grades
- Lightweight — 0.02 g/cm³ (7.8×10⁻⁴ lb/in³), better than 97% of polymer grades
- Low embodied carbon — 3 kg CO₂/kg, better than 83% of polymer grades
- Low, predictable mold shrinkage — 0.4%, better than 82% of polymer grades
Limitations
- Degrades in UV without stabilisers — 8/100, worse than 100% of polymer grades
- Poor heat conductor — 0.03 W/m·K (0.0173 BTU/hr·ft·°F), worse than 96% of polymer grades
- Low stiffness — 0 GPa (6.67×10⁻⁴ Msi), worse than 90% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
- Limited formability — 15/100, worse than 79% of polymer grades
C578 Type II GPS properties
Typical room-temperature values for C578 Type II GPS; 17 are specific to this condition. Other listed values are C578 Type II reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
C578 Type II GPS has a density of 0.02 g/cm³ (7.8×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical10
C578 Type II GPS has a tensile strength of 0.22 MPa (0.0319 ksi), weaker than 96% of polymer grades. Elongation at break is 4% and the elastic modulus is 0 GPa (6.67×10⁻⁴ Msi).
Thermal8
C578 Type II 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).
Electrical5
C578 Type II GPS is an electrical insulator with a dielectric strength of 2 kV/mm (50.8 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of polymer grades. UV resistance is not recommended.
Sustainability4
Producing a kilogram of C578 Type II GPS takes about 95 MJ of energy and emits 3 kg of CO₂ — less than 70% of polymer grades. Typical recycled content is 5%.
Manufacturability4
C578 Type II GPS's machinability is excellent (95/100, better than 100% of polymer grades); weldability fair (40/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C578 Type II GPS
Is C578 Type II easy to machine?
Cut with hot wire, band saw or CNC router at low feed; avoid melting smear and provide dust/fume extraction.
Can C578 Type II be welded?
Not welded conventionally; blocks are steam-fused during moulding and joints are made with EPS-compatible (water-based or hot-melt) adhesives or mechanical fasteners.
Can C578 Type II be formed, bent or molded?
Steam block moulding or shape moulding of pre-expanded beads; age blocks 3–7 days before cutting to let pentane escape and shrinkage stabilise.
What surface finishes work on C578 Type II?
Compatible with polymer-modified cement render, water-based coatings, foil/film facers and mesh; never use solvent-based paints, adhesives or spray foams that attack polystyrene.
C578 Type II 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)largely lost during aging/curing | 0.2 – 2 | 0.8 |
| polymeric brominated flame retardant (PoFR building grade only; replaced HBCD | 0.4 – 1.2 | 0.7 |
| nucleating & processing additives (waxes | 0.05 – 0.5 | 0.2 |
| polystyrene (from styrene monomer)expandable polystyrene bead resin | ≥ 96 (balance) | — |
C578 Type II GPS — frequently asked
What is C578 Type II GPS used for?
C578 Type II GPS is typically used for wall insulation panels, roof insulation, SIP cores and cold storage insulation. In short: mid-density C578 EPS; best cost-to-strength EPS; SIP and roof board standard.
What is the tensile strength of C578 Type II GPS?
C578 Type II GPS has a typical tensile strength of 0.22 MPa (0.0319 ksi) — weaker than 96% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type II GPS easy to machine?
Yes — machinability is rated excellent (95/100, better than 100% of polymer grades). Cut with hot wire, band saw or CNC router at low feed; avoid melting smear and provide dust/fume extraction.
Can C578 Type II GPS be welded?
With care — weldability is rated fair (40/100). Not welded conventionally; blocks are steam-fused during moulding and joints are made with EPS-compatible (water-based or hot-melt) adhesives or mechanical fasteners.
What surface finishes work on C578 Type II GPS?
Compatible with polymer-modified cement render, water-based coatings, foil/film facers and mesh; never use solvent-based paints, adhesives or spray foams that attack polystyrene.
Can C578 Type II GPS be formed, bent or molded?
Steam block moulding or shape moulding of pre-expanded beads; age blocks 3–7 days before cutting to let pentane escape and shrinkage stabilise.
What is the maximum service temperature of C578 Type II GPS?
C578 Type II GPS is rated for continuous use to about 75°C (167 °F), and briefly to 85°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C578 — Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- ASTM D6817 — Rigid Cellular Polystyrene Geofoam — ASTM International (2021)
- EPS Industry Alliance technical data sheets (physical properties by density) — EPS Industry Alliance (2023)
- Neopor / Styropor expandable polystyrene product information — BASF (2022)
- Cellular Solids: Structure and Properties — Cambridge University Press (1997)
- EPS ( B1 , 20–22 kg/m³) (2026)
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.