JIS A9521 XPS 3bB
Grade
JIS A9521
3bB = type 3, skin retained, compressive class B
Pick when low conductivity of 0.027 W/m·K must be carried at moderate load, ≥200 kPa, for inverted roofs and under-slab floor insulation.
Values for the 3bB condition
Other JIS A9521 XPS grades and fills
JIS A9521 XPS is listed in 7 conditions; see the grade overview at JIS A9521 XPS.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Type 1, skin retained, compressive class A | Choose the most economical general-purpose board, 22 kg/m³ at 0.037 W/m·K, for void fill and floor levelling layers where thermal performance is not critical. | — | 0.3 | 2 | — |
Type 2, skin retained, compressive class A | Pick as the cost-performance middle grade at 0.032 W/m·K for wall and roof insulation where the lowest Type 3 conductivity is not required. | — | 0.35 | 2 | — |
3bADefault Type 3, skin retained, compressive class A | Use as the default for external residential insulation: lowest conductivity at 0.027 W/m·K with the full extrusion skin retained for best water resistance. | — | 0.4 | 2 | — |
1bB/bC | Use where load matters more than lambda: same 0.037 W/m·K but 30 kg/m³ and ≥200/300 kPa compressive class for floor slabs and road sub-base layers. | — | 0.4 | 2 | — |
2bB/bC | Choose when moderate conductivity of 0.032 W/m·K must be combined with load bearing at 32 kg/m³, as in inverted roofs and parking decks. | — | 0.45 | 2 | — |
3bBThis page Type 3, skin retained, compressive class B | Pick when low conductivity of 0.027 W/m·K must be carried at moderate load, ≥200 kPa, for inverted roofs and under-slab floor insulation. | — | 0.5 | 2 | — |
Type 3, skin retained, compressive class C | Choose the highest load class, ≥300 kPa at 37 kg/m³ and 0.028 W/m·K, for parking decks, foundation perimeter insulation and cold-store floors. | — | 0.55 | 2 | — |
What is JIS A9521 XPS 3bB?
JIS A9521 XPS 3bB is JIS A9521 XPS in the 3bB grade — pick when low conductivity of 0.027 W/m·K must be carried at moderate load, ≥200 kPa, for inverted roofs and under-slab floor insulation. JIS A9521 XPS 3bB has a tensile strength of 0.5 MPa (0.0725 ksi), weaker than 89% of polymer grades. Elongation at break is 2% and the elastic modulus is 0.02 GPa (0.0022 Msi). JIS A9521 XPS 3bB has a density of 0.03 g/cm³ (0.0012 lb/in³), lighter than 92% of polymer grades. Its glass-transition temperature is 100°C (212 °F). 3bA is the default condition FabDigit quotes; 3bB is available on request or by drawing note.
Advantages
- Easy to machine — 89/100, better than 93% of polymer grades
- Lightweight — 0.03 g/cm³ (0.0012 lb/in³), better than 92% of polymer grades
Limitations
- Poor heat conductor — 0.03 W/m·K (0.0156 BTU/hr·ft·°F), worse than 99% of polymer grades
- Limited ductility — 2%, worse than 95% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Difficult to weld — 5/100, worse than 89% of polymer grades
- Low stiffness — 0.02 GPa (0.0022 Msi), worse than 77% of polymer grades
JIS A9521 XPS 3bB properties
Typical room-temperature values for JIS A9521 XPS 3bB; 17 are specific to this condition. Other listed values are JIS A9521 XPS reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
JIS A9521 XPS 3bB has a density of 0.03 g/cm³ (0.0012 lb/in³), lighter than 92% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical10
JIS A9521 XPS 3bB has a tensile strength of 0.5 MPa (0.0725 ksi), weaker than 89% of polymer grades. Elongation at break is 2% and the elastic modulus is 0.02 GPa (0.0022 Msi).
Thermal8
JIS A9521 XPS 3bB is rated for continuous service to 75°C (167 °F). It conducts heat at 0.03 W/m·K (0.0156 BTU/hr·ft·°F), worse than 99% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical3
JIS A9521 XPS 3bB 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.
Sustainability3
Producing a kilogram of JIS A9521 XPS 3bB takes about 100 MJ of energy and emits 4.5 kg of CO₂ — less than 61% of polymer grades. Typical recycled content is 10%.
Manufacturability4
JIS A9521 XPS 3bB's machinability is excellent (89/100, better than 93% of polymer grades); weldability not recommended (5/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with JIS A9521 XPS 3bB
Is JIS A9521 XPS easy to machine?
Hot wire, band saw or utility knife all work, with very low cutting resistance. Avoid excessive hot-wire temperature, which causes melt shrinkage and styrene fumes.
Can JIS A9521 XPS be welded?
Not weldable; joint boards with shiplap or tongue-and-groove edges sealed with polyurethane foam adhesive or dedicated jointing tape.
Can JIS A9521 XPS be formed, bent or molded?
Produced as board by extrusion foaming; on site it accepts only very slight cold curvature because it is brittle. Complex shapes are made by cutting or hot-wire carving.
What surface finishes work on JIS A9521 XPS?
Remove the surface skin or scarify it before applying cement-based render with reinforcing mesh. Do not use solvent-based adhesives or hot bitumen compounds, and cover the board promptly rather than leaving it in UV.
JIS A9521 XPS 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 |
|---|---|---|
| brominated polymeric flame retardantpolymeric brominated type, replaces HBCD | 0.5 – 2.5 | 1.2 |
| blowing agent residual (CO2 / HFO-1234zeresidual blowing agent; diffusion affects long-term conductivity | 0.5 – 3 | 1.5 |
| talc (nucleating agent)nucleating agent, controls cell size | 0.1 – 1 | 0.3 |
| graphite / carbon black (IR blocker, )added in some low-conductivity grey boards | 0 – 2 | 0 |
| polystyrene (PS )general-purpose or high-impact PS matrix, contains recycled PS | ≥ 94 (balance) | — |
JIS A9521 XPS 3bB — frequently asked
What is JIS A9521 XPS 3bB used for?
JIS A9521 XPS 3bB is typically used for roof insulation, foundation insulation and cold storage insulation. In short: lowest conductivity styrenic board; closed-cell, low water uptake; JIS load-class range.
What is the tensile strength of JIS A9521 XPS 3bB?
JIS A9521 XPS 3bB has a typical tensile strength of 0.5 MPa (0.0725 ksi) — weaker than 89% of polymer grades. Strength varies by condition: see the 7 listed tempers.
Is JIS A9521 XPS 3bB easy to machine?
Yes — machinability is rated excellent (89/100, better than 93% of polymer grades). Hot wire, band saw or utility knife all work, with very low cutting resistance. Avoid excessive hot-wire temperature, which causes melt shrinkage and styrene fumes.
Can JIS A9521 XPS 3bB be welded?
Not readily — weldability is rated not recommended (5/100). Not weldable; joint boards with shiplap or tongue-and-groove edges sealed with polyurethane foam adhesive or dedicated jointing tape.
What surface finishes work on JIS A9521 XPS 3bB?
Remove the surface skin or scarify it before applying cement-based render with reinforcing mesh. Do not use solvent-based adhesives or hot bitumen compounds, and cover the board promptly rather than leaving it in UV.
Can JIS A9521 XPS 3bB be formed, bent or molded?
Produced as board by extrusion foaming; on site it accepts only very slight cold curvature because it is brittle. Complex shapes are made by cutting or hot-wire carving.
What is the maximum service temperature of JIS A9521 XPS 3bB?
JIS A9521 XPS 3bB 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.
Sources
- JIS A 9521 (2022)
- STYROFOAM / Foamular XPS product data — DuPont Performance Building Solutions (2023)
- Engineered Materials Handbook: Engineering Plastics (PS foams) — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.