Semi-Rigid PU Foam
Semi-Rigid PU Foam sits between flexible and rigid polyurethane in stiffness, is typically polyester-polyol based and often open-cell for airflow, and is evaluated to ASTM D3574 and GB/T 11976.
Reference datasheet — Semi-Rigid PU Foam 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 SR-100 condition
Semi-Rigid PU Foam grades and fills
Semi-Rigid PU Foam is supplied in 9 conditions, soft to hard. SR-100 is the default FabDigit quotes; the values on this page are for it.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Energy-absorbing / crash-pad grade | Tuned low-resilience formulation with a long flat crush plateau for FMVSS 201 head-impact and helmet liners. | 0.1 | 0.45 | 60 | 28 Shore A |
Polyether-polyol semi-rigid foam | Substitute for the polyester default in humid, warm or wash-down service where hydrolytic ageing kills polyester foam. | 0.1 | 0.4 | 90 | 30 Shore A |
Flame-retardant semi-rigid foam | Use where interior burn-rate or transit fire codes apply; slight loss of tensile and elongation from FR loading. | 0.14 | 0.45 | 55 | 35 Shore A |
Light-stabilised / aliphatic-capped semi-rigid foam | For visible interior surfaces exposed to sunlight where yellowing of aromatic MDI foam is unacceptable. | 0.15 | 0.55 | 70 | 38 Shore A |
Low-density semi-rigid foam, ~60 kg/m³ | Lightest semi-rigid grade for soft-touch trim backing and light packaging cushions. | 0.3 | 85 | 20 Shore A | |
SR-100Default Standard semi-rigid polyester foam, ~100 kg/m³ | The default all-round semi-rigid density for energy-absorbing pads and instrument-panel backing. | 0.55 | 70 | 35 Shore A | |
Medium-high density semi-rigid foam, ~150 kg/m³ | Choose when higher crush plateau and dimensional stiffness are needed in thin sections. | 0.9 | 55 | 50 Shore A | |
High-density semi-rigid foam, ~250 kg/m³ | Structural-leaning grade for armrests, load-bearing pads and machinable tooling blocks. | 2 | 40 | 20 Shore D | |
Integral-skin (self-skinning) semi-rigid foam | Pick when a tough moulded skin and finished surface are required without a separate cover — steering wheels, grab handles, armrests. | 3 | 110 | 65 Shore A |
What is Semi-Rigid PU Foam?
Semi-Rigid PU Foam sits between flexible and rigid polyurethane in stiffness, is typically polyester-polyol based and often open-cell for airflow, and is evaluated to ASTM D3574 and GB/T 11976. It absorbs energy while holding its dimensions, which suits moulded interior substrates, filter media and die-cut gaskets; the default grade runs about 0.1 g/cm³ density, 0.55 MPa tensile strength, 70 % elongation and 0.01 GPa modulus. Service is limited to 90 °C, thermal conductivity is 0.04 W/m·K, and as a thermoset it cannot be welded or reground. Rigid PU foam is the choice for structural insulation, flexible foam for comfort duty. Semi-Rigid PU Foam has a density of 0.1 g/cm³ (0.0036 lb/in³), lighter than 86% of polymer grades. Its glass-transition temperature is 60°C (140 °F). Semi-Rigid PU Foam has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. Elongation at break is 70% and the elastic modulus is 0.01 GPa (0.0015 Msi).
What is Semi-Rigid PU Foam used for?
- automotive sun visors and headliners
- packaging energy-absorbing inserts
- air filter media substrate
- gasketing and sealing
Advantages
- Lightweight — 0.1 g/cm³ (0.0036 lb/in³), better than 86% of polymer grades
Limitations
- Absorbs moisture — dry before molding — 8%, worse than 100% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0231 BTU/hr·ft·°F), worse than 87% of polymer grades
- Low stiffness — 0.01 GPa (0.0015 Msi), worse than 81% of polymer grades
- Needs corrosion protection — 70/100, worse than 78% of polymer grades
- Degrades in UV without stabilisers — 25/100, worse than 76% of polymer grades
Semi-Rigid PU Foam properties
Typical room-temperature values for Semi-Rigid PU Foam-SR-100; bars are the position among polymer grades.
Physical4
Semi-Rigid PU Foam has a density of 0.1 g/cm³ (0.0036 lb/in³), lighter than 86% of polymer grades. Its glass-transition temperature is 60°C (140 °F).
Mechanical12
Semi-Rigid PU Foam has a tensile strength of 0.55 MPa (0.0798 ksi), weaker than 88% of polymer grades. Elongation at break is 70% and the elastic modulus is 0.01 GPa (0.0015 Msi).
Thermal8
Semi-Rigid PU Foam is rated for continuous service to 90°C (194 °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 70 µm/m·K (38.9 µin/in·°F).
Electrical3
Semi-Rigid PU Foam has an electrical resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of Semi-Rigid PU Foam takes about 100 MJ of energy and emits 4.6 kg of CO₂ — less than 61% of polymer grades. Typical recycled content is 5%.
Manufacturability4
Semi-Rigid PU Foam's machinability is good (55/100, worse than 64% of polymer grades); formability very good (75/100).
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. Semi-Rigid PU Foam is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Semi-Rigid PU Foam
Is Semi-Rigid PU Foam easy to machine?
Cut with band saw, oscillating knife, hot wire (skinned grades) or die; high-density blocks can be CNC routed with sharp single-flute cutters and strong vacuum extraction.
Can Semi-Rigid PU Foam be welded?
Not weldable; join by PU/hot-melt adhesive, flame lamination or in-mould bonding to substrates and skins.
Can Semi-Rigid PU Foam be formed, bent or molded?
Reaction-injected or poured into heated closed moulds at 35–60 °C with vent design and mould release; demould 3–8 min, full property build after 24 h post-cure.
Semi-Rigid PU Foam 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 |
|---|---|---|
| polyester polyol (or polyether polyol)B-component base resin | 40 – 60 | 50 |
| water (chemical blowing agent, CO2) | 1 – 4 | 2.5 |
| silicone surfactantcell regulator | 0.5 – 2 | 1.2 |
| amine / tin catalysts | 0.2 – 1.5 | 0.7 |
| chain extender / crosslinker (e.g. diethsets semi-rigid modulus | 0.5 – 4 | 2 |
| flame retardant (phosphate ester)FR variants only | 0 – 12 | 0 |
| polymeric MDI (isocyanate)A-component; index typ. 100–110 | ≥ 35 (balance) |
What surface finishes work on Semi-Rigid PU Foam?
Integral-skin parts accept flexible PU paint after mould-release removal and IR flash-off; open-cell grades are covered with fabric, TPO or PVC skin rather than painted.
Equivalent designations
Standards and trade names that resolve to Semi-Rigid PU Foam in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- D3574GB/T 11976
How much does Semi-Rigid PU Foam cost?
Semi-Rigid PU Foam 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.
Semi-Rigid PU Foam — frequently asked
What is Semi-Rigid PU Foam used for?
Semi-Rigid PU Foam is typically used for automotive sun visors and headliners, packaging energy-absorbing inserts, air filter media substrate and gasketing and sealing. In short: mid-stiffness energy absorber; dimensionally stable open-cell foam; bridges flexible and rigid PU.
What is the tensile strength of Semi-Rigid PU Foam?
Semi-Rigid PU Foam has a typical tensile strength of 0.55 MPa (0.0798 ksi) — weaker than 88% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is Semi-Rigid PU Foam easy to machine?
Reasonably — machinability is rated good (55/100, worse than 64% of polymer grades). Cut with band saw, oscillating knife, hot wire (skinned grades) or die; high-density blocks can be CNC routed with sharp single-flute cutters and strong vacuum extraction.
Can Semi-Rigid PU Foam be welded?
Not weldable; join by PU/hot-melt adhesive, flame lamination or in-mould bonding to substrates and skins.
What surface finishes work on Semi-Rigid PU Foam?
Integral-skin parts accept flexible PU paint after mould-release removal and IR flash-off; open-cell grades are covered with fabric, TPO or PVC skin rather than painted.
Can Semi-Rigid PU Foam be formed, bent or molded?
Reaction-injected or poured into heated closed moulds at 35–60 °C with vent design and mould release; demould 3–8 min, full property build after 24 h post-cure.
What is the maximum service temperature of Semi-Rigid PU Foam?
Semi-Rigid PU Foam is rated for continuous use to about 90°C (194 °F), and briefly to 120°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Semi-Rigid PU Foam SR-100 and Semi-Rigid PU Foam UV-ST?
SR-100 is the default condition — the default all-round semi-rigid density for energy-absorbing pads and instrument-panel backing. UV-ST: for visible interior surfaces exposed to sunlight where yellowing of aromatic MDI foam is unacceptable.
How much does Semi-Rigid PU Foam cost?
Semi-Rigid PU Foam 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 D3574 — Flexible Cellular Materials, Slab, Bonded and Molded Urethane Foams — ASTM International (2017)
- ASTM D1621 — Compressive Properties of Rigid Cellular Plastics — ASTM International (2016)
- Cellular Solids: Structure and Properties (Gibson & Ashby) — Cambridge University Press (1997)
- ASM Engineered Materials Handbook Vol. 2 — Engineering Plastics (cellular polymers) — ASM International (1988)
- Semi-rigid and integral-skin polyurethane system datasheets — Covestro / BASF / Huntsman (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.