C578 Type XV
ASTM C578 Type XV is the highest-density standard EPS grade in ASTM C578, a rigid closed-cell moulded styrenic foam made from pentane-loaded bead pre-expanded to about 48 kg/m³.
Reference datasheet — C578 Type XV 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.
Values for the FR condition
C578 Type XV grades and fills
C578 Type XV is supplied in 4 conditions, soft to hard. FR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
IR-absorbing bead for lower lambda | Pick when the thermal target cannot be met at this thickness; graphite lowers conductivity ~8–12 % but blocks are grey and sun-sensitive during storage. | — | 0.52 | 2.3 | — |
Geofoam block | Large sawn blocks certified to D6817 for embankment, bridge-approach and retaining-wall backfill where 1 % strain creep stress governs design. | — | 0.52 | 2.4 | — |
FRDefault Flame-retardant building/geofoam grade | Standard supply for construction: bead contains polymeric brominated FR so blocks meet C578 surface-burning limits. | — | 0.55 | 2.5 | — |
Additive-free grade for packaging, tooling patterns and industrial cores | Choose the additive-free grade where fire codes do not apply and any flame-retardant chemistry is unwanted: lost-foam foundry patterns, CNC model stock and food-adjacent packaging. | — | 0.55 | 2.6 | — |
What is C578 Type XV?
ASTM C578 Type XV is the highest-density standard EPS grade in ASTM C578, a rigid closed-cell moulded styrenic foam made from pentane-loaded bead pre-expanded to about 48 kg/m³. Engineers specify it where compressive strength governs, in heavy structural geofoam and high-load insulation, and it is supplied as block and cut shapes in flame-retardant, non-FR, graphite-loaded and geofoam versions. Thermal conductivity is 0.0335 W/m·K and maximum service temperature is 75 °C. It is not weldable, is attacked by solvents and hydrocarbons, and needs permanent UV cover; XPS Type VII or X suits high load combined with sustained wetting. C578 Type XV has a density of 0.05 g/cm³ (0.0017 lb/in³), lighter than 89% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type XV has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.02 GPa (0.0023 Msi).
What is C578 Type XV used for?
- Heavy structural geofoam
- Runway/road embankment fill
- High-load insulation
Advantages
- Easy to machine — 90/100, better than 95% of polymer grades
- Lightweight — 0.05 g/cm³ (0.0017 lb/in³), better than 89% of polymer grades
- Low embodied carbon — 3.3 kg CO₂/kg, better than 78% 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 (0.0194 BTU/hr·ft·°F), worse than 94% of polymer grades
- Limited ductility — 2.5%, worse than 89% of polymer grades
- Needs corrosion protection — 65/100, worse than 86% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
C578 Type XV properties
Typical room-temperature values for C578 Type XV-FR; bars are the position among polymer grades.
Physical4
C578 Type XV has a density of 0.05 g/cm³ (0.0017 lb/in³), lighter than 89% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical10
C578 Type XV has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.02 GPa (0.0023 Msi).
Thermal8
C578 Type XV is rated for continuous service to 75°C (167 °F). It conducts heat at 0.03 W/m·K (0.0194 BTU/hr·ft·°F), worse than 94% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical5
C578 Type XV is an electrical insulator with a dielectric strength of 2 kV/mm (50.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (65/100), worse than 86% of polymer grades. UV resistance is not recommended.
Sustainability4
Producing a kilogram of C578 Type XV takes about 105 MJ of energy and emits 3.3 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability4
C578 Type XV's machinability is excellent (90/100, better than 95% of polymer grades); weldability poor (30/100); 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 XV is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type XV
Is C578 Type XV easy to machine?
Hot-wire cutting gives the cleanest profiles; CNC router/bandsaw work well with sharp tools, high rpm and vacuum extraction, but avoid tool rub that melts and welds the kerf.
Can C578 Type XV be welded?
Not fusion-welded in practice — join with EPS-compatible water-based or solvent-free PU adhesives, or steam-fuse in the mould; solvent adhesives dissolve the foam.
Can C578 Type XV be formed, bent or molded?
Made by pre-expanding pentane-loaded bead to ~48 kg/m³, ageing, then steam block-moulding at ~110–120 °C; blocks must be aged/dried several days before sawing to control shrinkage and dimensional drift.
C578 Type XV 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)n-/iso-pentane, largely diffused out after ageing | 0.1 – 1.5 | 0.5 |
| polymeric brominated flame retardantFR grades only (HBCD-free polymeric FR) | 0.5 – 1.5 | 0.9 |
| graphitegrey/graphite-enhanced variant only | 0 – 4 | 0 |
| polystyrene (expandable PS bead)styrene homopolymer matrix | ≥ 96 (balance) | — |
What surface finishes work on C578 Type XV?
Coat or render only with water-based or cement-based systems (polymer-modified stucco, geotextile, EPDM/HDPE membrane); protect permanently from UV, hydrocarbon spills and temperatures above ~75 °C.
How much does C578 Type XV cost?
C578 Type XV 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 XV — frequently asked
What is C578 Type XV used for?
C578 Type XV is typically used for heavy structural geofoam, runway/road embankment fill and high-load insulation. In short: highest-density C578 EPS; maximum-load geofoam grade; graphite option for conductivity.
What is the tensile strength of C578 Type XV?
C578 Type XV has a typical tensile strength of 0.55 MPa (0.0798 ksi) — weaker than 88% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type XV easy to machine?
Yes — machinability is rated excellent (90/100, better than 95% of polymer grades). Hot-wire cutting gives the cleanest profiles; CNC router/bandsaw work well with sharp tools, high rpm and vacuum extraction, but avoid tool rub that melts and welds the kerf.
Can C578 Type XV be welded?
Not readily — weldability is rated poor (30/100). Not fusion-welded in practice — join with EPS-compatible water-based or solvent-free PU adhesives, or steam-fuse in the mould; solvent adhesives dissolve the foam.
What surface finishes work on C578 Type XV?
Coat or render only with water-based or cement-based systems (polymer-modified stucco, geotextile, EPDM/HDPE membrane); protect permanently from UV, hydrocarbon spills and temperatures above ~75 °C.
Can C578 Type XV be formed, bent or molded?
Made by pre-expanding pentane-loaded bead to ~48 kg/m³, ageing, then steam block-moulding at ~110–120 °C; blocks must be aged/dried several days before sawing to control shrinkage and dimensional drift.
What is the maximum service temperature of C578 Type XV?
C578 Type XV 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 XV cost?
C578 Type XV 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 D6817 — Standard Specification for Rigid Cellular Polystyrene Geofoam — ASTM International (2021)
- EPS Industry Alliance technical bulletins (thermal, mechanical, water absorption) — EPS-IA (2023)
- Engineered Materials Handbook, Vol. 2: Engineering Plastics (polystyrene foam) — ASM International (1988)
- High-density EPS geofoam and insulation board datasheets — various EPS moulders (ACH Foam/Atlas/Insulfoam class products) (2024)
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.