HDPE vs PP
Polymer · grade comparison
HDPE and PP are both polymer grades, both corrosion resistant plastic. PP is the stronger of the two: yield strength 33 MPa (4.79 ksi) against 26 MPa (3.77 ksi) for HDPE, about 27% more; tensile strength follows at 35 MPa (5.08 ksi) vs 28 MPa (4.06 ksi). In exchange, HDPE is the more ductile: elongation 600% versus 150% for PP, and PP is harder (72 Shore D vs 65 Shore D). PP is lighter (0.91 g/cm³ vs 0.96 g/cm³ for HDPE) and PP is stiffer (1.5 GPa vs 1.1 GPa). On the shop floor, HDPE machines more easily (very good vs good).
HDPEChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
PPChoose it when strength drives the design, or when weight is the constraint.
HDPE vs PP: 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
Shear Modulus
Bulk 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
Fracture Toughness (K_IC)
Izod Impact, Notched
Hardness, Shore D
Hardness, Rockwell R
Physical
Density and transition temperatures.
Density
Melting Temperature (Tm)
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Refractive Index
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
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
Vicat Softening Point (B50)
Max Service Temperature (short-term)
Same in both: Specific Heat Capacity 1,900 J/kg·K0.45 BTU/lb·°F · Limiting Oxygen Index 18%
Electrical
Conductivity and insulation.
Dielectric Strength
Dielectric Constant (1 MHz)
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · Dissipation Factor (1 MHz) 3×10⁻⁴ · Volume Resistivity 1×10¹⁶ Ω·cm · Surface Resistivity 1×10¹⁵ Ω · Comparative Tracking Index (CTI) 600 V
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
Melt Flow Rate
Same in both: Processing Melt Temperature (typ.) 230°C446 °F · Mold Temperature (typ.) 40°C104 °F
Sustainability
Primary-production footprint per kilogram.
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 78 MJ/kg33,534 BTU/lb · Embodied Carbon (primary production) 2 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 | HDPE | PP |
|---|---|---|
| 3D printing | — | Yes |
| Default condition | FDA Compliant | Homopolymer |
| Relative cost | $ Budget | $ Budget |
| Min. machined wall | 0.5 mm | 0.5 mm |
| Best machined surface | Ra 0.8 µm | Ra 0.8 µm |
| Conductive Coating | — | Yes |
| Dyeing (Nylon) | — | Yes |
| Primer Coating | — | Yes |
| Tinted Coating | — | Yes |
| Vacuum Metallization | — | Yes |
| Waterproof Coating | — | Yes |
Both are offered for CNC machining, Sheet metal and Injection molding. They share 6 finishes: Chrome Plating (Plastic), EMI Shielding Coating, Painting, Soft Touch Coating, Spray Painting, UV Coating.
HDPE vs PP — frequently asked
Is PP stronger than HDPE?
Yes. PP has a typical yield strength of 33 MPa (4.79 ksi) against 26 MPa (3.77 ksi) for HDPE — about 27% more. Tensile strength is 35 MPa (5.08 ksi) vs 28 MPa (4.06 ksi).
Which is cheaper, HDPE or PP?
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, HDPE or PP?
HDPE. Its machinability rates very good (75/100) against good (60/100) for PP.
Ready to make it?
Upload a CAD file and FabDigit prices the part in HDPE and PP 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.