Plastic HDPE vs. Plastic PLA

Compare Plastic HDPE vs. Plastic PLA strength, stiffness, weight and thermal properties.

Plastic HDPEBulk polymer (molded or machined)

Mechanical	Plastic HDPE	Plastic PLA
Yield strength	24MPa1	52.5MPa22.19x stronger
Ultimate tensile strength	not stated (yield given)	52.5MPa2
Flexural strength	not sourced	96.8MPa2
Elongation at break	not sourced	7.8%2
Young's modulus (stiffness)	0.9GPa1	3.25GPa23.61x stiffer
Density	950kg/m³131% lighter	1,240kg/m³2
Strength to weight	25.3kN·m/kg	42.3kN·m/kg1.68x higher
Stiffness to weight	0.947MN·m/kg	2.62MN·m/kg2.77x higher
Poisson's ratio	base material0.4–0.453	not sourced
Shear modulus	0.316GPa	not sourced
Bulk modulus	2GPa	not sourced
Speed of sound	973m/s	1,619m/s1.66x faster

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Plastic HDPE	Plastic PLA
Thermal conductivity	base material0.4–0.49W/m·K3	base material0.13W/m·K4
Thermal expansion	base material120µm/m·K3	not sourced
100 mm part over a 50 °C swing	600µm growth	not sourced
Specific heat	base material2,250J/kg·K31.88x higher	base material1,200J/kg·K4
Heats up and cools (diffusivity)	0.208mm²/s2.38x faster	0.0874mm²/s
Thermal shock resistance	56.9W/m	not sourced
Melting point	not sourced	152°C2
Glass transition	not sourced	59.1°C2
Max service temperature	not sourced	HDT 0.455 MPa58.8°C2

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources4 documents: LyondellBasell, UltiMaker, INEOS Olefins & Polymers USA, NatureWorks

Plastic HDPE: LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values
Plastic PLA: Ultimaker PLA, 3D-printed specimens, XY (flat) orientation; Ultimaker S5 Pro, engineering intent profile, 0.15 mm layer height, AA 0.4 print core, 100% infill, Cura 4.9, printed one-at-a-time, conditioned >=24 h at room temperature. TDS dated April 20, 2022.

1
Hostalen 23050 B Product DataLyondellBasellPlastic HDPE · Yield strength: typical, tensile stress at yield 23 °C, 50 mm/min ISO 527Plastic HDPE · Young's modulus (stiffness): typical, tensile modulus 23 °C ISO 527Plastic HDPE · Density: typical, ISO 1183
2
Ultimaker PLA Technical Data Sheet, v5.00UltiMakerarchived copyPlastic PLA · Yield strength: typicalPlastic PLA · Ultimate tensile strength: typical, peak stress (= stress at yield)Plastic PLA · Flexural strength: typicalPlastic PLA · Elongation at break: typicalPlastic PLA · Young's modulus (stiffness): typicalPlastic PLA · Density: typicalPlastic PLA · Melting point: typicalPlastic PLA · Glass transition: typicalPlastic PLA · Max service temperature: HDT 0.455 MPa (printed specimens)
3
Typical Engineering Properties of High Density PolyethyleneINEOS Olefins & Polymers USAarchived copyPlastic HDPE · Poisson's ratio: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal conductivity: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal expansion: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Specific heat: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)
4
Engineering Properties of Ingeo BiopolymerNatureWorksarchived copyPlastic PLA · Thermal conductivity: base material: NatureWorks Ingeo biopolymer, amorphous sheet, 25 °CPlastic PLA · Specific heat: base material: NatureWorks Ingeo biopolymer, amorphous sheet, 25 °C

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Plastic PLA is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Mechanical

Is Plastic HDPE stronger than Plastic PLA?

Plastic PLA is stronger: its yield strength is 52.5 MPa against 24 MPa for Plastic HDPE (2.19x).

Which is lighter, Plastic HDPE or Plastic PLA?

Plastic HDPE is lighter: 950 kg/m³ against 1,240 kg/m³ for Plastic PLA.

Which is stiffer, Plastic HDPE or Plastic PLA?

Plastic PLA is stiffer: Young's modulus 3.25 GPa against 0.9 GPa for Plastic HDPE, so the same part in Plastic PLA deflects less under the same load.

Which is lighter for the same job, Plastic HDPE or Plastic PLA?

For the same stiffness or strength: Plastic PLA is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Plastic HDPE	Plastic PLA
Stiff rod or tie (tension)	2.77x heavier	lighter
Stiff beam (bending)	46% heavier	lighter
Stiff panel or plate	18% heavier	lighter
Strong rod or tie	1.68x heavier	lighter
Strong beam	29% heavier	lighter
Strong panel or plate	13% heavier	lighter

For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).

Thermal

Which conducts heat better, Plastic HDPE or Plastic PLA?

Plastic HDPE conducts heat better: 0.445 W/m·K against 0.13 W/m·K for Plastic PLA.