Plastic UHMWPE vs. Steel AISI 1045

Compare Plastic UHMWPE vs. Steel AISI 1045 strength, stiffness, weight and thermal properties.

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Plastic UHMWPEBulk polymer (molded or machined)

Mechanical
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Yield strength	20MPasourcetypical, tensile stress at yield ISO 527, 50 mm/min	531MPasourceproducer-stated, cold drawn
Ultimate tensile strength	43MPasourcetypical, tensile stress at break ISO 527, 50 mm/min	627MPasourceproducer-stated, cold drawn
Elongation at break	465%sourcetypical, nominal elongation at break ISO 527	12%sourcein 2 in (50.8 mm)
Young's modulus (stiffness)	0.66GPasourcetypical, tensile modulus ISO 527, 1 mm/min	210GPasourcetypical
Density	930kg/m³sourcetypical8.39x lighter	7,800kg/m³sourcetypical
Strength to weight	21.5kN·m/kg	68.1kN·m/kg3.17x higher
Stiffness to weight	0.71MN·m/kg	26.9MN·m/kg37.9x higher
Poisson's ratio	not sourced	0.3sourcetypical
Shear modulus	not sourced	80.8GPa
Bulk modulus	not sourced	175GPa
Speed of sound	842m/s	5,189m/s
Thermal
Thermal conductivity	0.4W/m·Ksourcetypical, unfilled (narrative value, generic Celanese UHMWPE)	40–45W/m·Ksourcetypical range, ambient
Thermal expansion	200µm/m·Ksourcetypical, 20 to 100 °C (generic Celanese UHMWPE)	12µm/m·Ksourcetypical, mean 20-300 °C
100 mm part over a 50 °C swing	1,000µm growth	60µm growth16.7x less
Specific heat	not sourced	460–480J/kg·Ksourcetypical range, 50/100 °C
Heats up and cools (diffusivity)	not sourced	11.6mm²/s
Thermal shock resistance	not sourced	6,269W/m
Melting point	130–138°CsourceDSC 10 K/min	not sourced
Max service temperature	80°Csourcerecommended max constant operating temperature	not sourced
Values for	Celanese GUR 4120 (avg. molecular weight 4.7x10^6 g/mol), typical values on compression-molded specimens; CTE and thermal conductivity from Celanese's generic UHMWPE guide (grade not named)	AISI 1045 cold drawn bar (Niagara LaSalle) for mechanical; Ovako C45 (lists 'SAE 1045' as a similar designation) for physical constants

Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Is Plastic UHMWPE stronger than Steel AISI 1045?

Steel AISI 1045 is stronger: its yield strength is 531 MPa against 20 MPa for Plastic UHMWPE (26.6x).

Which is lighter, Plastic UHMWPE or Steel AISI 1045?

Plastic UHMWPE is lighter: 930 kg/m³ against 7,800 kg/m³ for Steel AISI 1045.

Which is stiffer, Plastic UHMWPE or Steel AISI 1045?

Steel AISI 1045 is stiffer: Young's modulus 210 GPa against 0.66 GPa for Plastic UHMWPE, so the same part in Steel AISI 1045 deflects less under the same load.

Which is lighter for the same job, Plastic UHMWPE or Steel AISI 1045?

For the same stiffness or strength: Plastic UHMWPE is lighter for a stiff panel or plate, strong panel or plate; Steel AISI 1045 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam.

Part that must be	Plastic UHMWPE	Steel AISI 1045
Stiff rod or tie (tension)	37.9x heavier	lighter
Stiff beam (bending)	2.13x heavier	lighter
Stiff panel or plate	lighter	23% heavier
Strong rod or tie	3.17x heavier	lighter
Strong beam	6% heavier	lighter
Strong panel or plate	lighter	1.63x heavier

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).

Which conducts heat better, Plastic UHMWPE or Steel AISI 1045?

Steel AISI 1045 conducts heat better: 42.5 W/m·K against 0.4 W/m·K for Plastic UHMWPE.

Which expands less with temperature?

Steel AISI 1045 expands less: 12 µm/m·K against 200 µm/m·K for Plastic UHMWPE.

Among 72 materials

Stiffness against density

Strength against density