EPS vs PS
Polymer · grade comparison
EPS and PS are both polymer grades. PS is the stronger of the two: yield strength 45 MPa (6.53 ksi) against 0.2 MPa (0.029 ksi) for EPS, about 225 times as much; tensile strength follows at 46 MPa (6.67 ksi) vs 0.25 MPa (0.0363 ksi). In exchange, EPS is the more ductile: elongation 3% versus 2.5% for PS. EPS is lighter (0.02 g/cm³ vs 1.05 g/cm³ for PS) and PS is stiffer (3.2 GPa vs 0.01 GPa). On the shop floor, EPS machines more easily (excellent vs good) and PS welds better (very good vs fair).
EPSChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
PSChoose it when strength drives the design, or when it will be welded.
EPS vs PS: 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
Shear Modulus
Bulk Modulus
Fracture Toughness (K_IC)
Izod Impact, Notched
Hardness, Shore D
Hardness, Rockwell M
Hardness, Rockwell R
Physical
Density and transition temperatures.
Density
Water Absorption (24 h)
Water Absorption (Saturation)
Refractive Index
Light Transmission
Same in both: Glass Transition (Tg) 100°C212 °F
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
Vicat Softening Point (B50)
Max Service Temperature (short-term)
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Same in both: Limiting Oxygen Index 18%
Electrical
Conductivity and insulation.
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Dielectric Strength
Surface Resistivity
Comparative Tracking Index (CTI)
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · Volume Resistivity 1×10¹⁶ Ω·cm
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)
Mold Temperature (typ.)
Polishability
Melt Flow Rate
Processing Melt Temperature (typ.)
Same in both: Mold Shrinkage 0.5%
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Water
Typical Recycled Content
Same in both: Embodied Carbon (primary production) 3.4 kg CO₂/kg
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
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 | EPS | PS |
|---|---|---|
| Default condition | — | — |
| Relative cost | $ Budget | $ Budget |
| Min. machined wall | — | — |
| Best machined surface | — | — |
EPS vs PS — frequently asked
Is PS stronger than EPS?
Yes. PS has a typical yield strength of 45 MPa (6.53 ksi) against 0.2 MPa (0.029 ksi) for EPS — about 225 times as much. Tensile strength is 46 MPa (6.67 ksi) vs 0.25 MPa (0.0363 ksi).
Which is cheaper, EPS or PS?
Both sit in the same relative cost tier ($, budget); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, EPS or PS?
EPS. Its machinability rates excellent (90/100) against good (60/100) for PS; for welding the order is PS first (very good, 70/100) then EPS (fair, 45/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in EPS and PS 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.