Plastic TPU vs. Rubber

Compare Plastic TPU vs. Rubber strength, stiffness, weight and thermal properties.

RubberBulk polymer (molded or machined)

Mechanical	Plastic TPU	Rubber
Yield strength	not given (tensile used)	not given (tensile used)
Ultimate tensile strength	23.7MPa1	23MPa2
Flexural strength	4.1MPa1	not sourced
Elongation at break	not sourced	830%2
Young's modulus (stiffness)	0.067GPa1	not sourced
Density	1,220kg/m³1	960kg/m³227% lighter
Strength to weight	19.4kN·m/kg	24kN·m/kg23% higher
Stiffness to weight	0.0549MN·m/kg	not sourced
Poisson's ratio	not sourced	government0.53
Shear modulus	not sourced	not sourced
Bulk modulus	not sourced	not sourced
Speed of sound	234m/s	not sourced

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Plastic TPU	Rubber
Thermal conductivity	not sourced	0.151W/m·K4
Thermal expansion	not sourced	not sourced
100 mm part over a 50 °C swing	not sourced	not sourced
Specific heat	not sourced	government1,881J/kg·K3
Heats up and cools (diffusivity)	not sourced	0.0836mm²/s
Thermal shock resistance	not sourced	not sourced
Melting point	217°C1	not sourced
Max service temperature	HDT 0.455 MPa50.3°C1	70°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: UltiMaker, Weir Minerals, National Institute of Standards and Technology, Defense Technical Information Center

Plastic TPU: Ultimaker TPU 95A, 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 (file v5.00), April 29, 2022.
Rubber: Weir Minerals Linatex Premium rubber (95 % natural rubber), typical physical properties, spec sheet WMD0118/202305

1
Ultimaker TPU 95A Technical Data Sheet, v5.00UltiMakerarchived copyPlastic TPU · Ultimate tensile strength: typical, stress at breakPlastic TPU · Flexural strength: typicalPlastic TPU · Young's modulus (stiffness): typicalPlastic TPU · Density: typicalPlastic TPU · Melting point: typicalPlastic TPU · Max service temperature: HDT 0.455 MPa (printed specimens)
2
Linatex Premium Rubber Spec Sheet (WMD0118, 2023)Weir MineralsRubber · Ultimate tensile strength: typicalRubber · Elongation at break: typicalRubber · Density: typical (specific gravity)Rubber · Max service temperature: continuous use operating range
3
Compressibility of Natural Rubber at Pressures Below 500 kg/cm², J. Res. NBS 68A (1964)National Institute of Standards and Technologyarchived copyRubber · Poisson's ratio: government (NBS J. Res. 68A, 1964): computed by NBS for peroxide-cured gum NR vulcanizate, 25 °C, infinitesimal deformation (0.49 in the solver: the linear element locks as the ratio nears 0.5 (nearly incompressible).)Rubber · Specific heat: government (NBS J. Res. 68A, Table 7; values observed for unvulcanized NR by Bekkedahl and Matheson), 25 °C
4
Thermal Conductivity of Soft Vulcanized Natural Rubber: Selected Values (AD 643325)Defense Technical Information Centerarchived copyRubber · Thermal conductivity: government selected value (US Army Natick Laboratories TR 66-49-PR, 1966), soft vulcanized natural rubber, 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 TPU is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Mechanical

Is Plastic TPU stronger than Rubber?

Plastic TPU is stronger: its tensile strength is 23.7 MPa against 23 MPa for Rubber (3%).

Which is lighter, Plastic TPU or Rubber?

Rubber is lighter: 960 kg/m³ against 1,220 kg/m³ for Plastic TPU.

Which is lighter for the same job, Plastic TPU or Rubber?

For the same stiffness or strength: Rubber is lighter for a strong rod or tie, strong beam, strong panel or plate.

Part that must be	Plastic TPU	Rubber
Strong rod or tie	23% heavier	lighter
Strong beam	25% heavier	lighter
Strong panel or plate	25% 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).