C578 Type VII
ASTM C578 Type VII is a high-density closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, extruded with a dissolved blowing agent for heavy-load service.
Reference datasheet — C578 Type VII 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 VII grades and fills
C578 Type VII is supplied in one standard condition, FR-B1.
Supply forms, finishes and certifications
Ways C578 Type VII is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
GRV | Grooved / drainage-channel board | Surface finish |
FACED | Film- or mat-faced board | Coating |
STDDefault | Standard unfaced board | Standard supply |
What is C578 Type VII?
ASTM C578 Type VII is a high-density closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, extruded with a dissolved blowing agent for heavy-load service. Engineers specify it under airport pavements, cold storage floors and trafficked decks, and it is stocked plain, grooved, faced and in flame-retardant (B1) versions with a thermal conductivity of 0.029 W/m·K. It is supplied as board only: heating above about 80 °C collapses the cell structure and destroys the R-value. Not weldable and not UV-stable, so it must be covered; Type VI is adequate where compressive loads are lower. C578 Type VII has a density of 0.04 g/cm³ (0.0013 lb/in³), lighter than 91% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type VII has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. The elastic modulus is 0.02 GPa (0.0029 Msi).
What is C578 Type VII used for?
- Airport pavement insulation
- Cold storage floor insulation
- Heavy traffic deck insulation
Advantages
- Lightweight — 0.04 g/cm³ (0.0013 lb/in³), better than 91% of polymer grades
- Easy to machine — 85/100, better than 88% of polymer grades
- Low moisture uptake — 0.1%, better than 77% of polymer grades
Limitations
- Poor heat conductor — 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Low stiffness — 0.02 GPa (0.0029 Msi), worse than 75% of polymer grades
C578 Type VII properties
Typical room-temperature values; bars are the position among polymer grades.
Physical4
C578 Type VII has a density of 0.04 g/cm³ (0.0013 lb/in³), lighter than 91% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical8
C578 Type VII has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. The elastic modulus is 0.02 GPa (0.0029 Msi).
Thermal8
C578 Type VII is rated for continuous service to 75°C (167 °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).
Electrical1
Chemical & Environmental2
UV resistance is poor.
Sustainability4
Producing a kilogram of C578 Type VII takes about 105 MJ of energy and emits 5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 10%.
Manufacturability4
C578 Type VII's machinability is excellent (85/100, better than 88% of polymer grades); weldability poor (20/100); formability poor (25/100).
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 VII is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type VII
Is C578 Type VII easy to machine?
Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC shaping are easy but generate static-clinging dust — use vacuum extraction.
Can C578 Type VII be welded?
Not weldable; boards are joined by shiplap/ship-edge interlock, foam-compatible polyurethane adhesive or mechanical plates.
Can C578 Type VII be formed, bent or molded?
Supplied as extruded board only; no post-forming — thermal shaping above ~80 °C collapses the cells and destroys R-value.
C578 Type VII 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 |
|---|---|---|
| polymeric brominated flame retardantbutadiene-styrene brominated copolymer, replaces legacy HBCD | 0.5 – 2.5 | 1.2 |
| nucleating agent (talc) | 0.3 – 1.5 | 0.8 |
| residual blowing agent (CO2 / HFO-1234ze | 0.5 – 3 | 1.5 |
| polystyrene (general-purpose PS resin)may include post-industrial PS regrind | ≥ 92 (balance) | — |
What surface finishes work on C578 Type VII?
Protect from UV and solvents: cover with slab concrete, screed, cement-board render or mat facer; use only water-based or foam-safe adhesives and coatings.
How much does C578 Type VII cost?
C578 Type VII is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C578 Type VII — frequently asked
What is C578 Type VII used for?
C578 Type VII is typically used for airport pavement insulation, cold storage floor insulation and heavy traffic deck insulation. In short: heavy-load XPS board; cold-store floor grade; available flame-retardant B1.
What is the tensile strength of C578 Type VII?
C578 Type VII has a typical tensile strength of 0.55 MPa (0.0798 ksi) — weaker than 88% of polymer grades.
Is C578 Type VII easy to machine?
Yes — machinability is rated excellent (85/100, better than 88% of polymer grades). Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC shaping are easy but generate static-clinging dust — use vacuum extraction.
Can C578 Type VII be welded?
Not readily — weldability is rated poor (20/100). Not weldable; boards are joined by shiplap/ship-edge interlock, foam-compatible polyurethane adhesive or mechanical plates.
What surface finishes work on C578 Type VII?
Protect from UV and solvents: cover with slab concrete, screed, cement-board render or mat facer; use only water-based or foam-safe adhesives and coatings.
Can C578 Type VII be formed, bent or molded?
Supplied as extruded board only; no post-forming — thermal shaping above ~80 °C collapses the cells and destroys R-value.
What is the maximum service temperature of C578 Type VII?
C578 Type VII is rated for continuous use to about 75°C (167 °F), and briefly to 85°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type VII cost?
C578 Type VII is a standard-cost polymer ($$), 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)
- ASTM D1621 / D1623 / C203 / C272 / C518 test methods for rigid cellular plastics — ASTM International (2021)
- Extruded polystyrene board technical data (60 psi / high-load grades) — Owens Corning / DuPont / Kingspan (2023)
- Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
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.