Poron ExtraFirm
Grade
also Microcellular Urethane
For load spreading, bumpers and vibration isolation pads where deflection must stay small under continuous load.
Values for the ExtraFirm condition
Other Poron grades and fills
Poron is listed in 6 conditions; see the grade overview at Poron.
Compare all 6 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
ultra-low CFD grades (e.g. PORON 4790-92-15/-20, EVExtend very soft) | Use where closure force must be minimal — thin-wall plastic housings, OLED module cushions, low-force dust seals. | — | 0.6 | 180 | 10 Shore A |
High strain-rate impact-protection urethane | Rate-sensitive grade that stiffens on impact — used in protective sports/PPE padding and drop protection rather than static gasketing. | — | 0.9 | 180 | 15 Shore A |
Flame-retardant grades | Required for battery packs, power supplies and automotive interiors needing a V-0 or FMVSS 302 rated cushion. | — | 1 | 140 | 22 Shore A |
Sealing grade for IP-rated water/dust resistance | Choose for IPX4–IPX7 style gaskets in phones and wearables where thin, low-force water sealing is needed. | — | 1 | 150 | 25 Shore A |
Higher-density/firmer microcellular urethane | Pick when the pad must carry higher load or resist thinning under sustained clamp force, e.g. structural standoff and vibration pads. | — | 2 | 140 | 28 Shore A |
ExtraFirmThis page highest-density load-bearing grades (e.g. PORON 4701-50, HP firm) | For load spreading, bumpers and vibration isolation pads where deflection must stay small under continuous load. | — | 2 | 120 | 35 Shore A |
What is Poron ExtraFirm?
Poron ExtraFirm is Poron in the ExtraFirm grade — for load spreading, bumpers and vibration isolation pads where deflection must stay small under continuous load. Poron ExtraFirm has a tensile strength of 2 MPa (0.29 ksi), weaker than 84% of polymer grades. Elongation at break is 120% and the elastic modulus is 0 GPa (5.08×10⁻⁴ Msi). Poron ExtraFirm has a density of 0.58 g/cm³ (0.021 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Advantages
- Lightweight — 0.58 g/cm³ (0.021 lb/in³), better than 84% of polymer grades
- Easy to machine — 75/100, better than 78% of polymer grades
- Forms and bends easily — 80/100, better than 75% of polymer grades
Limitations
- Absorbs moisture — dry before molding — 3%, worse than 99% of polymer grades
- Low stiffness — 0 GPa (5.08×10⁻⁴ Msi), worse than 92% of polymer grades
- Poor heat conductor — 0.08 W/m·K (0.0462 BTU/hr·ft·°F), worse than 83% of polymer grades
- Needs corrosion protection — 70/100, worse than 78% of polymer grades
Poron ExtraFirm properties
Typical room-temperature values for Poron ExtraFirm; 16 are specific to this condition. Other listed values are Poron reference data and may not represent this condition. Bars are the position among polymer grades.
Physical3
Poron ExtraFirm has a density of 0.58 g/cm³ (0.021 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -35°C (-31 °F).
Mechanical9
Poron ExtraFirm has a tensile strength of 2 MPa (0.29 ksi), weaker than 84% of polymer grades. Elongation at break is 120% and the elastic modulus is 0 GPa (5.08×10⁻⁴ Msi).
Thermal6
Poron ExtraFirm is rated for continuous service to 90°C (194 °F). It conducts heat at 0.08 W/m·K (0.0462 BTU/hr·ft·°F), worse than 83% of polymer grades.
Electrical2
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is fair.
Sustainability3
Producing a kilogram of Poron ExtraFirm takes about 100 MJ of energy and emits 5 kg of CO₂ — less than 61% of polymer grades. Typical recycled content is 0%.
Manufacturability2
Poron ExtraFirm's machinability is very good (75/100, better than 78% of polymer grades); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Poron ExtraFirm
Is Poron easy to machine?
Convert by steel-rule die, rotary kiss-cut, laser (with fume extraction) or waterjet; avoid conventional milling — the foam tears and compresses under tool load.
Can Poron be welded?
Not weldable; join with acrylic PSA transfer tape, urethane adhesive or mechanical capture in a housing groove.
Can Poron be formed, bent or molded?
Supplied as cast/skived sheet and roll; forms only by compression in the assembly — design for 20–50 % working deflection and avoid >70 % compression to preserve recovery.
What surface finishes work on Poron?
No coating needed; surfaces are as-skived or film/PSA laminated, and can be printed or laminated with PET/PI films for low-friction or shielding layers.
Poron 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/polyether polyolsoft-segment backbone; ether-type used for hydrolysis-resistant grades | 50 – 70 | 60 |
| diisocyanate (MDI/TDI)hard-segment / crosslinker | 20 – 40 | 30 |
| cell-control additives, surfactants, pigmicrocellular structure control | 2 – 10 | 5 |
| flame retardant (FR grades only)present only in UL 94 V-0 variants | 0 – 15 | 8 |
Poron ExtraFirm — frequently asked
What is Poron ExtraFirm used for?
Poron ExtraFirm is typically used for electronic enclosure sealing gaskets, vibration and shock dampers, display and touchscreen cushions, wearable device skin-contact padding, impact padding in protective gear and battery pack compression pads. In short: cushioning microcellular urethane.
What is the tensile strength of Poron ExtraFirm?
Poron ExtraFirm has a typical tensile strength of 2 MPa (0.29 ksi) — weaker than 84% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is Poron ExtraFirm easy to machine?
Yes — machinability is rated very good (75/100, better than 78% of polymer grades). Convert by steel-rule die, rotary kiss-cut, laser (with fume extraction) or waterjet; avoid conventional milling — the foam tears and compresses under tool load.
Can Poron ExtraFirm be welded?
Not weldable; join with acrylic PSA transfer tape, urethane adhesive or mechanical capture in a housing groove.
What surface finishes work on Poron ExtraFirm?
No coating needed; surfaces are as-skived or film/PSA laminated, and can be printed or laminated with PET/PI films for low-friction or shielding layers.
Can Poron ExtraFirm be formed, bent or molded?
Supplied as cast/skived sheet and roll; forms only by compression in the assembly — design for 20–50 % working deflection and avoid >70 % compression to preserve recovery.
What is the maximum service temperature of Poron ExtraFirm?
Poron ExtraFirm 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.
Can FabDigit make parts in Poron ExtraFirm?
Yes — Poron ExtraFirm is available for injection molding; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- PORON Microcellular Urethane Product Data (4701 / 4790 series, AquaPro, XRD) — Rogers Corporation (2023)
- ASTM D1056 — Flexible Cellular Materials, Sponge or Expanded Rubber — ASTM (2020)
- ASTM D3574 — Flexible Cellular Materials, Slab, Bonded and Molded Urethane Foams — ASTM (2017)
- UL 94 — Tests for Flammability of Plastic Materials — UL (2020)
- Polyurethane Handbook (structure–property data for microcellular elastomers) — Hanser (1994)
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.