C578 Type XI
ASTM C578 Type XI is the lightest molded EPS grade in the ASTM C578 family, a very low-density bead foam with a thermal conductivity of about 0.039 W/m·K, used where weight and cost dominate and mechanical strength is not a design factor.
Reference datasheet — C578 Type XI 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 XI grades and fills
C578 Type XI is supplied in 3 conditions, soft to hard. FR is the default FabDigit quotes; the values on this page are for it.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
FRDefault Flame-retardant block-molded board | Default construction/insulation board: FR bead (polymeric brominated FR replacing HBCD), cut from aged block to ASTM C578 Type XI. | — | 0.08 | 2.5 | — |
Packaging / void-fill grade without flame retardant | Cheapest option for packaging, void fill and floats where no building fire code applies. | — | 0.08 | 2.5 | — |
Steam shape-molded parts | Pick when the geometry is molded directly (cushions, corner blocks, ICF-style forms) rather than cut from block. | — | 0.09 | 2.5 | — |
Supply forms, finishes and certifications
Ways C578 Type XI 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 / foil / scrim laminated board | Coating |
What is C578 Type XI?
ASTM C578 Type XI is the lightest molded EPS grade in the ASTM C578 family, a very low-density bead foam with a thermal conductivity of about 0.039 W/m·K, used where weight and cost dominate and mechanical strength is not a design factor. It is supplied as molded block, hot-wire-cut sheet and shape-molded parts, in fire-retardant and non-FR bead and with facers. It crumbles under point load or clamping pressure, is dissolved by solvent-based paints and cements, and needs UV protection. Choose Type I or Type VIII where any compressive load is carried. C578 Type XI has a density of 0.01 g/cm³ (4.34×10⁻⁴ lb/in³), lighter than 100% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type XI has a tensile strength of 0.08 MPa (0.0116 ksi), weaker than 100% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi).
What is C578 Type XI used for?
- Lightweight packaging
- Non-structural void fill
- Model/craft foam
Advantages
- Lightweight — 0.01 g/cm³ (4.34×10⁻⁴ lb/in³), better than 100% of polymer grades
- Low embodied carbon — 3.3 kg CO₂/kg, better than 78% of polymer grades
Limitations
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Low stiffness — 0 GPa (3.19×10⁻⁴ Msi), worse than 94% of polymer grades
- Limited ductility — 2.5%, worse than 89% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0225 BTU/hr·ft·°F), worse than 88% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
C578 Type XI properties
Typical room-temperature values for C578 Type XI-FR; bars are the position among polymer grades.
Physical4
C578 Type XI has a density of 0.01 g/cm³ (4.34×10⁻⁴ lb/in³), lighter than 100% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical9
C578 Type XI has a tensile strength of 0.08 MPa (0.0116 ksi), weaker than 100% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi).
Thermal9
C578 Type XI is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0225 BTU/hr·ft·°F), worse than 88% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical3
C578 Type XI has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of C578 Type XI 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 XI's machinability is good (55/100, worse than 64% of polymer grades); weldability poor (25/100); formability poor (15/100).
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 XI is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type XI
Is C578 Type XI easy to machine?
Cut with hot wire, hot knife or fine-tooth band saw; router/CNC works dry with vacuum extraction, but low-density foam crumbles under any clamping force and generates static bead dust.
Can C578 Type XI be welded?
Not weldable in the conventional sense — join with water-based or foam-safe polyurethane/EPS adhesives, or heat-fuse skins; solvent-based cements dissolve the foam.
Can C578 Type XI be formed, bent or molded?
Made by pre-expanding beads with pentane, aging, then steam block-molding (~0.5–1.0 bar, 105–120 °C) and hot-wire cutting; shape moulding needs long dwell for the very low fill weight.
C578 Type XI 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)up to ~5-6 % in unexpanded bead; largely diffused out after aging | 0.2 – 3 | 1 |
| polymeric brominated flame retardantFR grades only; HBCD-free pFR since ~2015 | 0.3 – 1.5 | 0.8 |
| air (cell gas)>97 % of volume | — | — |
| polystyrene (styrene homopolymer)expanded bead matrix | ≥ 90 (balance) | — |
What surface finishes work on C578 Type XI?
Accepts cement- or acrylic-based renders, water-based paints, and laminated facers; requires a protective coat or facer against UV, mechanical damage and solvent contact.
How much does C578 Type XI cost?
C578 Type XI is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C578 Type XI — frequently asked
What is C578 Type XI used for?
C578 Type XI is typically used for lightweight packaging, non-structural void fill and model/craft foam. In short: lightest C578 EPS; lowest-cost bead foam; non-structural use only.
What is the tensile strength of C578 Type XI?
C578 Type XI has a typical tensile strength of 0.08 MPa (0.0116 ksi) — weaker than 100% of polymer grades. Strength varies by condition: see the 3 listed tempers.
Is C578 Type XI easy to machine?
Reasonably — machinability is rated good (55/100, worse than 64% of polymer grades). Cut with hot wire, hot knife or fine-tooth band saw; router/CNC works dry with vacuum extraction, but low-density foam crumbles under any clamping force and generates static bead dust.
Can C578 Type XI be welded?
Not readily — weldability is rated poor (25/100). Not weldable in the conventional sense — join with water-based or foam-safe polyurethane/EPS adhesives, or heat-fuse skins; solvent-based cements dissolve the foam.
What surface finishes work on C578 Type XI?
Accepts cement- or acrylic-based renders, water-based paints, and laminated facers; requires a protective coat or facer against UV, mechanical damage and solvent contact.
Can C578 Type XI be formed, bent or molded?
Made by pre-expanding beads with pentane, aging, then steam block-molding (~0.5–1.0 bar, 105–120 °C) and hot-wire cutting; shape moulding needs long dwell for the very low fill weight.
What is the maximum service temperature of C578 Type XI?
C578 Type XI is rated for continuous use to about 75°C (167 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type XI cost?
C578 Type XI is a standard-cost polymer ($$), 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 10801.1 (EPS) — SAC (2021)
- ASM Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
- EPS insulation board technical data (block-molded, 12–16 kg/m³) — EPS Industry Alliance / member producers (2023)
- Inventory of Carbon & Energy (ICE) — EPS foam — University of Bath / Circular Ecology (2019)
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.