RIM PU Foam vs SPF
Polymer · grade comparison
RIM PU Foam and SPF are both polymer grades. RIM PU Foam is the stronger of the two: tensile strength 12 MPa (1.74 ksi) against 0.3 MPa (0.0435 ksi) for SPF, about 40 times as much. RIM PU Foam is the more ductile: elongation 130% versus 8% for SPF. SPF is lighter (0.03 g/cm³ vs 0.6 g/cm³ for RIM PU Foam) and RIM PU Foam is stiffer (0.22 GPa vs 0.01 GPa). On the shop floor, SPF machines more easily (excellent vs good).
RIM PU FoamChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
SPFChoose it when weight is the constraint, or when the part is machined in volume.
RIM PU Foam vs SPF: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Izod Impact, Notched
Hardness, Shore A
Hardness, Shore D
Tear Strength
Compression Set (22 h, 70 °C)
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Limiting Oxygen Index
Max Service Temperature (short-term)
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Surface Resistivity
Comparative Tracking Index (CTI)
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Polishability
Mold Shrinkage
Processing Melt Temperature (typ.)
Mold Temperature (typ.)
Sustainability
Primary-production footprint per kilogram.
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 105 MJ/kg45,142 BTU/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every polymer grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | RIM PU Foam | SPF |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
RIM PU Foam vs SPF — frequently asked
Is RIM PU Foam stronger than SPF?
Yes. RIM PU Foam has a typical tensile strength of 12 MPa (1.74 ksi) against 0.3 MPa (0.0435 ksi) for SPF — about 40 times as much.
Which is cheaper, RIM PU Foam or SPF?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, RIM PU Foam or SPF?
SPF. Its machinability rates excellent (85/100) against good (55/100) for RIM PU Foam; for welding the order is RIM PU Foam first (not recommended, 10/100) then SPF (not recommended, 5/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in RIM PU Foam and SPF side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.