C578 Type X
ASTM C578 Type X is a very high-density closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, made by tandem extrusion of polystyrene melt with a dissolved blowing agent.
Reference datasheet — C578 Type X 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 X grades and fills
C578 Type X 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 |
|---|---|---|---|---|---|
Grooved / channelled drainage board | Foundation-wall board with drainage grooves; choose for backfilled walls needing hydrostatic relief. | 0.18 | 0.22 | 3 | — |
Shiplap / tongue-and-groove edge board | Use where board-to-board joints must block air and thermal bridging without taping. | 0.25 | 0.3 | 3 | — |
Low-GWP HFO / CO₂-blown formulation | Specify for green-building credits and codes phasing out HFC blowing agents; same Type X mechanicals, slightly different aged R. | 0.25 | 0.3 | 3 | — |
GB 8624 B1 fire-rated board | Chinese building code grade with elevated FR loading for façade and roof insulation. | 0.32 | 0.4 | 2.5 | — |
Supply forms, finishes and certifications
Ways C578 Type X 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 | Film- or mat-faced board | Coating |
PLANED | Planed / shaved surface board | Coating |
STDDefault | Standard unfaced board, square edge, extrusion skin | Standard supply |
What is C578 Type X?
ASTM C578 Type X is a very high-density closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, made by tandem extrusion of polystyrene melt with a dissolved blowing agent. It is specified for the most demanding structural insulation loads and comes plain, planed, shiplap-edged, drainage-grooved, faced, HFO-blown and flame-retardant (B1), with a thermal conductivity of 0.029 W/m·K. Downstream work is limited to cutting, grooving and skiving; there is no post-forming, and the foam is not UV-stable or solvent-resistant. Type VII covers slightly lower load cases at lower cost. C578 Type X has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type X has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 94% of polymer grades. The elastic modulus is 0.01 GPa (0.001 Msi).
What is C578 Type X used for?
- Heavy structural fill under slabs
- High-load roof and deck insulation
- Protected membrane roofs with paver ballast
- Parking and plaza deck insulation
- Airport and highway pavement insulation
- Freezer and cold-storage floor insulation
- Shiplap-edge continuous exterior insulation
Advantages
- Lightweight — 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), better than 97% of polymer grades
- Easy to machine — 90/100, better than 95% of polymer grades
- Low moisture uptake — 0.1%, better than 77% of polymer grades
Limitations
- Degrades in UV without stabilisers — 12/100, worse than 99% of polymer grades
- Poor heat conductor — 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades
- Low stiffness — 0.01 GPa (0.001 Msi), worse than 84% of polymer grades
C578 Type X properties
Typical room-temperature values; bars are the position among polymer grades.
Physical4
C578 Type X has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical9
C578 Type X has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 94% of polymer grades. The elastic modulus is 0.01 GPa (0.001 Msi).
Thermal8
C578 Type X is rated for continuous service to 74°C (165 °F). It conducts heat at 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical4
C578 Type X has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
UV resistance is not recommended.
Sustainability3
Producing a kilogram of C578 Type X takes about 105 MJ of energy and emits 5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 10%.
Manufacturability3
C578 Type X's machinability is excellent (90/100, better than 95% of polymer grades); formability poor (20/100).
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 X is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type X
Is C578 Type X easy to machine?
Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC hot-wire shaping are easy but generate static-clinging dust — vacuum extraction helps.
Can C578 Type X be welded?
Not weldable in the metal sense; boards are joined by shiplap laps, tape, foam-safe adhesive or mechanical washer fasteners, and can be hot-plate/heat fused only in specialist panel lines.
Can C578 Type X be formed, bent or molded?
Produced by tandem extrusion of PS melt with dissolved blowing agent through a slot die into a calibrator; downstream shaping is limited to cutting, grooving and skiving — no post-forming.
C578 Type X 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 |
|---|---|---|
| blowing agent (CO₂, HFO-1234ze, HFC-134aresidual cell gas + dissolved agent | 1.5 – 6 | 3.5 |
| flame retardant (polymeric brominated st | 0.7 – 3 | 1.5 |
| nucleating agent (talc) | 0.1 – 1 | 0.4 |
| pigment / IR attenuator (carbon, graphit | 0 – 1.5 | 0.3 |
| polystyrene (general-purpose PS, virgin matrix resin | ≥ 90 (balance) | — |
What surface finishes work on C578 Type X?
Never leave exposed to sunlight; overcoat with cementitious base coat/EIFS on planed board, or cover with cladding, and use only water-based or XPS-compatible (solvent-free) adhesives, membranes and mastics.
How much does C578 Type X cost?
C578 Type X 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 X — frequently asked
What is C578 Type X used for?
C578 Type X is typically used for heavy structural fill under slabs, high-load roof and deck insulation, protected membrane roofs with paver ballast, parking and plaza deck insulation, airport and highway pavement insulation and freezer and cold-storage floor insulation. In short: highest-load XPS grade; shiplap and HFO options; cut-only, no post-forming.
What is the tensile strength of C578 Type X?
C578 Type X has a typical tensile strength of 0.3 MPa (0.0435 ksi) — weaker than 94% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type X easy to machine?
Yes — machinability is rated excellent (90/100, better than 95% of polymer grades). Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC hot-wire shaping are easy but generate static-clinging dust — vacuum extraction helps.
Can C578 Type X be welded?
Not weldable in the metal sense; boards are joined by shiplap laps, tape, foam-safe adhesive or mechanical washer fasteners, and can be hot-plate/heat fused only in specialist panel lines.
What surface finishes work on C578 Type X?
Never leave exposed to sunlight; overcoat with cementitious base coat/EIFS on planed board, or cover with cladding, and use only water-based or XPS-compatible (solvent-free) adhesives, membranes and mastics.
Can C578 Type X be formed, bent or molded?
Produced by tandem extrusion of PS melt with dissolved blowing agent through a slot die into a calibrator; downstream shaping is limited to cutting, grooving and skiving — no post-forming.
What is the maximum service temperature of C578 Type X?
C578 Type X is rated for continuous use to about 74°C (165 °F), and briefly to 85°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type X cost?
C578 Type X 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 — Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- GB/T 10801.2 — Extruded polystyrene board (XPS) for thermal insulation — SAC (2018)
- Extruded polystyrene insulation board technical data (FOAMULAR / STYROFOAM class products) — Owens Corning / DuPont Performance Building Solutions (2023)
- Handbook of Polymeric Foams and Foam Technology — Hanser (2004)
- Rigid polystyrene foam property and LCA records — Granta / ICE inventory (2022)
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.