Plastic PETG vs. Rubber

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

RubberBulk polymer (molded or machined)

Mechanical	Plastic PETG	Rubber
Yield strength	46.2MPa1	not given (tensile used)
Ultimate tensile strength	46.2MPa12.01x stronger	23MPa2
Flexural strength	78.9MPa1	not sourced
Elongation at break	7.6%1	830%2109x more ductile
Young's modulus (stiffness)	1.94GPa1	not sourced
Density	1,270kg/m³1	960kg/m³232% lighter
Strength to weight	36.4kN·m/kg1.52x higher	24kN·m/kg
Stiffness to weight	1.53MN·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	1,236m/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 PETG	Rubber
Thermal conductivity	base material0.21W/m·K439% more heat through a fin	0.151W/m·K5
Thermal expansion	base material51µm/m·K4	not sourced
100 mm part over a 50 °C swing	255µm growth	not sourced
Specific heat	base material1,300J/kg·K4	government1,881J/kg·K345% higher
Heats up and cools (diffusivity)	0.127mm²/s1.52x faster	0.0836mm²/s
Thermal shock resistance	not sourced	not sourced
Glass transition	77.4°C1	not sourced
Max service temperature	HDT 0.455 MPa76.2°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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Sources5 documents: UltiMaker, Weir Minerals, National Institute of Standards and Technology, Eastman, Defense Technical Information Center

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.
Rubber: Weir Minerals Linatex Premium rubber (95 % natural rubber), typical physical properties, spec sheet WMD0118/202305

1
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)
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
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)
5
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 PETG is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Mechanical

Is Plastic PETG stronger than Rubber?

Plastic PETG is stronger: its yield strength is 46.2 MPa against tensile strength 23 MPa for Rubber (2.01x).

Which is lighter, Plastic PETG or Rubber?

Rubber is lighter: 960 kg/m³ against 1,270 kg/m³ for Plastic PETG.

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

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

Part that must be	Plastic PETG	Rubber
Strong rod or tie	lighter	1.52x heavier
Strong beam	lighter	20% heavier
Strong panel or plate	lighter	7% 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 is more ductile, Plastic PETG or Rubber?

Rubber stretches further before it breaks: 830% elongation at break against 7.6% for Plastic PETG.

Thermal

Which conducts heat better, Plastic PETG or Rubber?

Plastic PETG conducts heat better: 0.21 W/m·K against 0.151 W/m·K for Rubber.