Plastic HDPE vs. Plastic PETG

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

Plastic HDPEBulk polymer (molded or machined)

Mechanical	Plastic HDPE	Plastic PETG
Yield strength	24MPa1	46.2MPa21.93x stronger
Ultimate tensile strength	not stated (yield given)	46.2MPa2
Flexural strength	not sourced	78.9MPa2
Elongation at break	not sourced	7.6%2
Young's modulus (stiffness)	0.9GPa1	1.94GPa22.15x stiffer
Density	950kg/m³134% lighter	1,270kg/m³2
Strength to weight	25.3kN·m/kg	36.4kN·m/kg44% higher
Stiffness to weight	0.947MN·m/kg	1.53MN·m/kg1.61x 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	1,236m/s27% 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 PETG
Thermal conductivity	base material0.4–0.49W/m·K3	base material0.21W/m·K4
Thermal expansion	base material120µm/m·K3	base material51µm/m·K42.35x less
100 mm part over a 50 °C swing	600µm growth	255µm growth2.35x less
Specific heat	base material2,250J/kg·K31.73x higher	base material1,300J/kg·K4
Heats up and cools (diffusivity)	0.208mm²/s1.64x faster	0.127mm²/s
Thermal shock resistance	56.9W/m	not sourced
Glass transition	not sourced	77.4°C2
Max service temperature	not sourced	HDT 0.455 MPa76.2°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, Eastman

Plastic HDPE: LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values
Plastic PETG: Ultimaker PETG, 3D-printed specimens, XY (flat); 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 v1.00, April 29, 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 PETG Technical Data Sheet, v1.00UltiMakerarchived copyPlastic PETG · Yield strength: typicalPlastic PETG · Ultimate tensile strength: typical, peak stress (= stress at yield)Plastic PETG · Flexural strength: typicalPlastic PETG · Elongation at break: typicalPlastic PETG · Young's modulus (stiffness): typicalPlastic PETG · Density: typicalPlastic PETG · Glass transition: typicalPlastic PETG · 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
Eastar Copolyester 6763 Product Data SheetEastmanPlastic PETG · Thermal conductivity: base material: Eastman Eastar Copolyester 6763 (PETG), typicalPlastic PETG · Thermal expansion: base material: Eastman Eastar Copolyester 6763 (PETG), typicalPlastic PETG · Specific heat: base material: Eastman Eastar Copolyester 6763 (PETG), DSC at 60 °C (lowest temperature listed)

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

Questions

Mechanical

Is Plastic HDPE stronger than Plastic PETG?

Plastic PETG is stronger: its yield strength is 46.2 MPa against 24 MPa for Plastic HDPE (1.93x).

Which is lighter, Plastic HDPE or Plastic PETG?

Plastic HDPE is lighter: 950 kg/m³ against 1,270 kg/m³ for Plastic PETG.

Which is stiffer, Plastic HDPE or Plastic PETG?

Plastic PETG is stiffer: Young's modulus 1.94 GPa against 0.9 GPa for Plastic HDPE, so the same part in Plastic PETG deflects less under the same load.

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

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

Part that must be	Plastic HDPE	Plastic PETG
Stiff rod or tie (tension)	1.61x heavier	lighter
Stiff beam (bending)	10% heavier	lighter
Stiff panel or plate	lighter	4% heavier
Strong rod or tie	44% heavier	lighter
Strong beam	16% heavier	lighter
Strong panel or plate	4% 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 PETG?

Plastic HDPE conducts heat better: 0.445 W/m·K against 0.21 W/m·K for Plastic PETG.

Which expands less with temperature?

Plastic PETG expands less: 51 µm/m·K against 120 µm/m·K for Plastic HDPE.