PMI Foam S
Heat-treated state
S = high-temperature-stable general grade
Cost-effective grade for high-temperature tooling cores and long dwell cure cycles.
Values for the S condition
Other PMI Foam grades and fills
PMI Foam is listed in 15 conditions; see the grade overview at PMI Foam.
Compare all 15 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
32 kg/m³ prepreg-grade PMI foam | Lowest-density grade: pick for minimum-weight, low-load radome and interior sandwich panels. | — | 1 | 3.5 | — |
in-mould foamed / particle-foam PMI | Use for complex near-net-shape cores moulded directly from PMI granules, avoiding block machining waste. | — | 1 | 3 | — |
52 kg/m³ prepreg-grade PMI foam | Most common lightweight core for sporting goods, antenna and light aircraft panels. | — | 2 | 3.5 | — |
52 kg/m³ high-temperature PMI foam | Light WF-family core for 180 °C/0.7 MPa autoclave cure cycles where IG would creep. | — | 2 | 3 | — |
Low-loss radome grade | Radome and antenna cores where dielectric constant and loss tangent are the controlling properties. | — | 2 | 3 | — |
High-elongation / damage-tolerant PMI foam | Use where impact damage tolerance and elongation matter more than peak modulus (leading edges, sports gear). | — | 2 | 8 | — |
71IGDefault 75 kg/m³ prepreg-grade PMI foam (standard) | The all-round default: best strength/weight compromise for autoclave-cured aerospace sandwich parts. | — | 2 | 3 | — |
75 kg/m³ high-temperature PMI foam | Standard high-temperature core: higher shear stiffness than 71 IG and cure-stable to ~200 °C. | — | 2 | 3 | — |
Fine-cell, sealed-skin prepreg grade | Pick when low resin uptake and a smooth skin-to-core bond line matter (thin prepreg face sheets). | — | 2 | 4.5 | — |
Resin-infusion / RTM optimised PMI foam | Select for liquid-composite moulding: low resin uptake surface and dimensional stability under injection pressure. | — | 4 | 4 | — |
SThis page High-temperature-stable general grade | Cost-effective grade for high-temperature tooling cores and long dwell cure cycles. | — | 4 | 3.5 | — |
110 kg/m³ prepreg-grade PMI foam | Choose where core shear/crush loads or fastener bearing are high, e.g. helicopter rotor blades and control surfaces. | — | 4 | 3 | — |
110 kg/m³ high-temperature PMI foam | High-load, high-temperature core for rotor blades, engine nacelle and RTM/prepreg tooling cores. | — | 4 | 3 | — |
205 kg/m³ high-temperature PMI foam | Dense grade for locally reinforced inserts, fastener/hard-point areas and press-cure tooling. | — | 7 | 3.5 | — |
~300 kg/m³ high-density PMI foam | Highest-density standard grade: bearing pads, edge close-outs and machined tooling blocks. | — | 11 | 3.5 | — |
What is PMI Foam S?
PMI Foam S is PMI Foam heat treated to S — cost-effective grade for high-temperature tooling cores and long dwell cure cycles. PMI Foam S has a tensile strength of 4 MPa (0.508 ksi), weaker than 83% of polymer grades. Elongation at break is 3.5% and the elastic modulus is 0.18 GPa (0.0261 Msi). PMI Foam S has a density of 0.11 g/cm³ (0.004 lb/in³), lighter than 86% of polymer grades. Its glass-transition temperature is 190°C (374 °F). 71IG is the default condition FabDigit quotes; S is available on request or by drawing note.
Advantages
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
- Lightweight — 0.11 g/cm³ (0.004 lb/in³), better than 86% of polymer grades
- Easy to machine — 80/100, better than 84% of polymer grades
Limitations
- Hard to polish — 10/100, worse than 98% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades
- High embodied carbon — 8 kg CO₂/kg, worse than 83% of polymer grades
- Limited ductility — 3.5%, worse than 79% of polymer grades
PMI Foam S properties
Typical room-temperature values for PMI Foam S; 15 are specific to this condition. Other listed values are PMI Foam reference data and may not represent this condition. Bars are the position among polymer grades.
Physical2
PMI Foam S has a density of 0.11 g/cm³ (0.004 lb/in³), lighter than 86% of polymer grades. Its glass-transition temperature is 190°C (374 °F).
Mechanical9
PMI Foam S has a tensile strength of 4 MPa (0.508 ksi), weaker than 83% of polymer grades. Elongation at break is 3.5% and the elastic modulus is 0.18 GPa (0.0261 Msi).
Thermal7
PMI Foam S is rated for continuous service to 200°C (392 °F). It conducts heat at 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades. Thermal expansion is 36 µm/m·K (20 µin/in·°F).
Electrical2
Chemical & Environmental2
UV resistance is fair.
Sustainability3
Producing a kilogram of PMI Foam S takes about 140 MJ of energy and emits 8 kg of CO₂ — more than 81% of polymer grades. Typical recycled content is 0%.
Manufacturability3
PMI Foam S's machinability is very good (80/100, better than 84% of polymer grades); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PMI Foam S
Is PMI Foam easy to machine?
CNC-mills, saws, sands and hot-wire cuts easily with sharp tools and vacuum extraction; the dust is abrasive and irritant, so seal machined faces before bonding.
Can PMI Foam be welded?
Not weldable in the metals sense; sections are joined with epoxy paste adhesive or splice films, or thermally fused during hot forming.
Can PMI Foam be formed, bent or molded?
Hot-form flat blanks at about 180–200 °C over a tool (short soak, cool under restraint); IG grades tolerate 0.3 MPa autoclave pressure and WF grades up to ~0.7 MPa — dry the core 2–4 h at 100–130 °C before cure to prevent blistering.
What surface finishes work on PMI Foam?
No plating or polishing; finish by resin/adhesive skinning, filling with lightweight epoxy paste, or bonding prepreg face sheets, then paint the laminate rather than the foam.
PMI 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 |
|---|---|---|
| methacrylic acid (monomer unit)imidized with methacrylonitrile to form the polymethacrylimide ring | 45 – 60 | 52 |
| methacrylonitrile (monomer unit) | 40 – 55 | 46 |
| cross-linker / blowing agent residues (fexpansion agents and additives; exact package proprietary | 0.5 – 3 | 2 |
| polymethacrylimide matrixclosed-cell solid phase; ~95 vol % gas at 75 kg/m³ | balance | — |
PMI Foam S — frequently asked
What is PMI Foam S used for?
PMI Foam S is typically used for aircraft sandwich panel cores, radome and wind blade cores, automotive/motorsport composite cores and prosthetics and sporting goods cores. In short: autoclave-capable foam core; highest stiffness-to-weight core; hot-formable closed-cell foam.
What is the tensile strength of PMI Foam S?
PMI Foam S has a typical tensile strength of 4 MPa (0.508 ksi) — weaker than 83% of polymer grades. Strength varies by condition: see the 15 listed tempers.
Is PMI Foam S easy to machine?
Yes — machinability is rated very good (80/100, better than 84% of polymer grades). CNC-mills, saws, sands and hot-wire cuts easily with sharp tools and vacuum extraction; the dust is abrasive and irritant, so seal machined faces before bonding.
Can PMI Foam S be welded?
Not weldable in the metals sense; sections are joined with epoxy paste adhesive or splice films, or thermally fused during hot forming.
What surface finishes work on PMI Foam S?
No plating or polishing; finish by resin/adhesive skinning, filling with lightweight epoxy paste, or bonding prepreg face sheets, then paint the laminate rather than the foam.
Can PMI Foam S be formed, bent or molded?
Hot-form flat blanks at about 180–200 °C over a tool (short soak, cool under restraint); IG grades tolerate 0.3 MPa autoclave pressure and WF grades up to ~0.7 MPa — dry the core 2–4 h at 100–130 °C before cure to prevent blistering.
What is the maximum service temperature of PMI Foam S?
PMI Foam S is rated for continuous use to about 200°C (392 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ROHACELL IG / IG-F Product Information — Evonik Industries (2023)
- ROHACELL WF Product Information — Evonik Industries (2023)
- ROHACELL HERO / RIST / Triple F technical brochures — Evonik Industries (2022)
- ASM Handbook Vol. 21: Composites — Sandwich Core Materials — ASM International (2001)
- ASTM C365 / C273 / C297 (core compression, shear and flatwise tension test methods) — ASTM (2022)
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.