Plastic HDPE vs. Plastic Nylon PA66

Compare Plastic HDPE vs. Plastic Nylon PA66 strength, stiffness, weight and thermal properties.

Plastic HDPEBulk polymer (molded or machined)

Plastic Nylon PA66Bulk polymer (molded or machined)

Mechanical	Plastic HDPE	Plastic Nylon PA66
Yield strength	24MPa1	85MPa23.54x stronger
Ultimate tensile strength	not stated (yield given)	not stated (yield given)
Elongation at break	not sourced	30%2
Young's modulus (stiffness)	0.9GPa1	3GPa23.33x stiffer
Density	950kg/m³119% lighter	1,130kg/m³2
Strength to weight	25.3kN·m/kg	75.2kN·m/kg2.98x higher
Stiffness to weight	0.947MN·m/kg	2.65MN·m/kg2.8x higher
Poisson's ratio	base material0.4–0.453	base material0.44
Shear modulus	0.316GPa	1.07GPa3.39x stiffer in shear
Bulk modulus	2GPa	5GPa2.5x higher
Speed of sound	973m/s	1,629m/s1.67x 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 Nylon PA66
Thermal conductivity	base material0.4–0.49W/m·K3	0.33W/m·K2
Thermal expansion	base material120µm/m·K3	longitudinal98µm/m·K222% less
100 mm part over a 50 °C swing	600µm growth	490µm growth22% less
Specific heat	base material2,250J/kg·K332% higher	1,700J/kg·K2
Heats up and cools (diffusivity)	0.208mm²/s21% faster	0.172mm²/s
Thermal shock resistance	56.9W/m	57.2W/m
Melting point	not sourced	DSC260°C2
Max service temperature	not sourced	101°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, BASF, INEOS Olefins & Polymers USA, Covestro

Plastic HDPE: LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values
Plastic Nylon PA66: BASF Ultramid A3K (PA66, unreinforced injection-moulding grade), Product Information 02/2026, dry values (ISO methods)

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
Ultramid A3K Product InformationBASFPlastic Nylon PA66 · Yield strength: typical, dryPlastic Nylon PA66 · Elongation at break: nominal strain at break, dryPlastic Nylon PA66 · Young's modulus (stiffness): typical, dryPlastic Nylon PA66 · Density: typicalPlastic Nylon PA66 · Thermal conductivity: typicalPlastic Nylon PA66 · Thermal expansion: longitudinal, 23-55 °CPlastic Nylon PA66 · Specific heat: typicalPlastic Nylon PA66 · Melting point: DSCPlastic Nylon PA66 · Max service temperature: IEC 60216 temperature index, 20000 h
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 Polymers Part and Mold Design: Thermoplastics, A Design GuideCovestroPlastic Nylon PA66 · Poisson's ratio: base material: unfilled polyamide (PA), conditioned, maker design-guide family value (Covestro Table 3-1)

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.

Questions

Mechanical

Is Plastic HDPE stronger than Plastic Nylon PA66?

Plastic Nylon PA66 is stronger: its yield strength is 85 MPa against 24 MPa for Plastic HDPE (3.54x).

Which is lighter, Plastic HDPE or Plastic Nylon PA66?

Plastic HDPE is lighter: 950 kg/m³ against 1,130 kg/m³ for Plastic Nylon PA66.

Which is stiffer, Plastic HDPE or Plastic Nylon PA66?

Plastic Nylon PA66 is stiffer: Young's modulus 3 GPa against 0.9 GPa for Plastic HDPE, so the same part in Plastic Nylon PA66 deflects less under the same load.

Which is lighter for the same job, Plastic HDPE or Plastic Nylon PA66?

For the same stiffness or strength: Plastic Nylon PA66 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 Nylon PA66
Stiff rod or tie (tension)	2.8x heavier	lighter
Stiff beam (bending)	1.53x heavier	lighter
Stiff panel or plate	26% heavier	lighter
Strong rod or tie	2.98x heavier	lighter
Strong beam	1.95x heavier	lighter
Strong panel or plate	1.58x 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 Nylon PA66?

Plastic HDPE conducts heat better: 0.445 W/m·K against 0.33 W/m·K for Plastic Nylon PA66.

Which expands less with temperature?

Plastic Nylon PA66 expands less: 98 µm/m·K against 120 µm/m·K for Plastic HDPE.