C578 Type I
ASTM C578 Type I is the lowest-density grade of molded expanded polystyrene (EPS) covered by the ASTM C578 board family, at roughly 14.4 kg/m³ (0.015 g/cm³) with a thermal conductivity near 0.04 W/m·K.
Reference datasheet — C578 Type I 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 I grades and fills
C578 Type I is supplied in 5 conditions, soft to hard.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
EPS15 geofoam block | Same nominal density supplied as large lightweight-fill blocks specified by strain-level compressive resistance rather than by C578 board properties. | — | 0.1 | 2 | — |
Non-flame-retardant packaging EPS | Cheapest bead for cushioning, fish boxes and void fill where no building fire requirement applies; does not satisfy the C578 LOI clause. | — | 0.13 | 2 | — |
Antistatic / static-dissipative EPS packaging | Choose for electronics and PCB packaging where surface charge must bleed off; antistatic agent is coated or compounded into the bead. | — | 0.13 | 2 | — |
Graphite-enhanced grey EPS | Pick when the same thickness must deliver 15–20 % better R-value; infrared-absorbing graphite lowers conductivity at identical low density. | — | 0.14 | 2 | — |
Shape-molded (tool-molded) EPS parts | Use when the part geometry is molded directly in a tool (helmet liners, appliance packs, EPS forms) instead of cut from block; skin gives slightly better surface strength. | — | 0.15 | 2 | — |
Supply forms, finishes and certifications
Ways C578 Type I is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
STDDefault | Standard white FR-modified block-molded EPS | Standard supply |
What is C578 Type I?
ASTM C578 Type I is the lowest-density grade of molded expanded polystyrene (EPS) covered by the ASTM C578 board family, at roughly 14.4 kg/m³ (0.015 g/cm³) with a thermal conductivity near 0.04 W/m·K. Engineers specify it where insulation value per unit cost matters more than strength; it is supplied as molded block, hot-wire- or saw-cut board and shape-molded parts. Compressive strength is the lowest in the family and the service limit is about 75 °C, so it is not suitable for bearing slabs and is attacked by solvents and UV. Step up to Type VIII or Type IX where load is carried. C578 Type I has a density of 0.02 g/cm³ (5.42×10⁻⁴ lb/in³), lighter than 100% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type I has a tensile strength of 0.13 MPa (0.0189 ksi), weaker than 98% of polymer grades. The elastic modulus is 0 GPa (4.35×10⁻⁴ Msi).
What is C578 Type I used for?
- Under-slab insulation
- Void fill
- Packaging blocks
- Low-load cavity fill
Advantages
- Lightweight — 0.02 g/cm³ (5.42×10⁻⁴ lb/in³), better than 100% of polymer grades
- Easy to machine — 85/100, better than 88% of polymer grades
- Low, predictable mold shrinkage — 0.4%, better than 82% 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
- Low stiffness — 0 GPa (4.35×10⁻⁴ Msi), worse than 92% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0231 BTU/hr·ft·°F), worse than 87% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
- Needs corrosion protection — 70/100, worse than 78% of polymer grades
C578 Type I properties
Typical room-temperature values; bars are the position among polymer grades.
Physical4
C578 Type I has a density of 0.02 g/cm³ (5.42×10⁻⁴ lb/in³), lighter than 100% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical7
C578 Type I has a tensile strength of 0.13 MPa (0.0189 ksi), weaker than 98% of polymer grades. The elastic modulus is 0 GPa (4.35×10⁻⁴ Msi).
Thermal9
C578 Type I is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0231 BTU/hr·ft·°F), worse than 87% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is not recommended.
Sustainability4
Producing a kilogram of C578 Type I 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 I's machinability is excellent (85/100, better than 88% of polymer grades); weldability poor (30/100).
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 I is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type I
Is C578 Type I easy to machine?
Hot-wire cutting gives the cleanest edge; band saw, router or CNC hot-knife also work, but keep tools sharp and avoid solvent coolants — dry cutting leaves static-clinging bead dust.
Can C578 Type I be welded?
No conventional welding: blocks and parts are joined by steam fusion in the mold, by hot-plate/hot-wire tacking, or with water-based/EPS-safe adhesives.
Can C578 Type I be formed, bent or molded?
Pre-expand bead with steam to the target 14–16 kg/m³, age 6–24 h, then steam-mold blocks or shapes at ~0.5–1.0 bar; blocks must be cured several days before cutting to stabilize dimensions.
C578 Type I 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 (blowing agent, residual)n-/iso-pentane; largely diffused out after ageing | 0.2 – 6 | 3 |
| polymeric brominated flame retardantpolymeric FR (HBCD-free) in building grade; absent in non-FR packaging bead | 0.5 – 1.5 | 0.9 |
| nucleating / coating agents (waxes, steabead surface coating for fusion and antistatic control | 0.1 – 0.8 | 0.3 |
| air (closed cells)≈98 % by volume of the finished foam, not by weight | ≈ 98 | 98 |
| polystyrene (styrene homopolymer)expandable bead base resin | ≥ 90 (balance) | — |
What surface finishes work on C578 Type I?
Coat only with water-based or EPS-compatible paints, cement/acrylic renders or laminated facers; solvent-based paints, bituminous primers and PVC plasticizers dissolve or shrink the foam, and all exposed surfaces need UV protection.
How much does C578 Type I cost?
C578 Type I 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 I — frequently asked
What is C578 Type I used for?
C578 Type I is typically used for under-slab insulation, void fill, packaging blocks and low-load cavity fill. In short: lowest-density C578 EPS; lowest-cost insulating foam; non-load-bearing fill only.
What is the tensile strength of C578 Type I?
C578 Type I has a typical tensile strength of 0.13 MPa (0.0189 ksi) — weaker than 98% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is C578 Type I easy to machine?
Yes — machinability is rated excellent (85/100, better than 88% of polymer grades). Hot-wire cutting gives the cleanest edge; band saw, router or CNC hot-knife also work, but keep tools sharp and avoid solvent coolants — dry cutting leaves static-clinging bead dust.
Can C578 Type I be welded?
Not readily — weldability is rated poor (30/100). No conventional welding: blocks and parts are joined by steam fusion in the mold, by hot-plate/hot-wire tacking, or with water-based/EPS-safe adhesives.
What surface finishes work on C578 Type I?
Coat only with water-based or EPS-compatible paints, cement/acrylic renders or laminated facers; solvent-based paints, bituminous primers and PVC plasticizers dissolve or shrink the foam, and all exposed surfaces need UV protection.
Can C578 Type I be formed, bent or molded?
Pre-expand bead with steam to the target 14–16 kg/m³, age 6–24 h, then steam-mold blocks or shapes at ~0.5–1.0 bar; blocks must be cured several days before cutting to stabilize dimensions.
What is the maximum service temperature of C578 Type I?
C578 Type I 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 I cost?
C578 Type I 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)
- Handbook of Polymeric Foams and Foam Technology — Hanser (2004)
- EPS insulation board technical data (density, R-value, compressive resistance) — EPS Industry Alliance / BASF Neopor (2023)
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.