Plastic PLA vs. Rubber

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

RubberBulk polymer (molded or machined)

Mechanical	Plastic PLA	Rubber
Yield strength	52.5MPa1	not given (tensile used)
Ultimate tensile strength	52.5MPa12.28x stronger	23MPa2
Flexural strength	96.8MPa1	not sourced
Elongation at break	7.8%1	830%2106x more ductile
Young's modulus (stiffness)	3.25GPa1	not sourced
Density	1,240kg/m³1	960kg/m³229% lighter
Strength to weight	42.3kN·m/kg1.77x higher	24kN·m/kg
Stiffness to weight	2.62MN·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	1,619m/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 PLA	Rubber
Thermal conductivity	base material0.13W/m·K4	0.151W/m·K516% more heat through a fin
Thermal expansion	not sourced	not sourced
100 mm part over a 50 °C swing	not sourced	not sourced
Specific heat	base material1,200J/kg·K4	government1,881J/kg·K31.57x higher
Heats up and cools (diffusivity)	0.0874mm²/s4% faster	0.0836mm²/s
Thermal shock resistance	not sourced	not sourced
Melting point	152°C1	not sourced
Glass transition	59.1°C1	not sourced
Max service temperature	HDT 0.455 MPa58.8°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, NatureWorks, Defense Technical Information Center

Plastic PLA: Ultimaker PLA, 3D-printed specimens, XY (flat) orientation; 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 dated April 20, 2022.
Rubber: Weir Minerals Linatex Premium rubber (95 % natural rubber), typical physical properties, spec sheet WMD0118/202305

1
Ultimaker PLA Technical Data Sheet, v5.00UltiMakerarchived copyPlastic PLA · Yield strength: typicalPlastic PLA · Ultimate tensile strength: typical, peak stress (= stress at yield)Plastic PLA · Flexural strength: typicalPlastic PLA · Elongation at break: typicalPlastic PLA · Young's modulus (stiffness): typicalPlastic PLA · Density: typicalPlastic PLA · Melting point: typicalPlastic PLA · Glass transition: typicalPlastic PLA · 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
Engineering Properties of Ingeo BiopolymerNatureWorksarchived copyPlastic PLA · Thermal conductivity: base material: NatureWorks Ingeo biopolymer, amorphous sheet, 25 °CPlastic PLA · Specific heat: base material: NatureWorks Ingeo biopolymer, amorphous sheet, 25 °C
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 PLA is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Mechanical

Is Plastic PLA stronger than Rubber?

Plastic PLA is stronger: its yield strength is 52.5 MPa against tensile strength 23 MPa for Rubber (2.28x).

Which is lighter, Plastic PLA or Rubber?

Rubber is lighter: 960 kg/m³ against 1,240 kg/m³ for Plastic PLA.

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

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

Part that must be	Plastic PLA	Rubber
Strong rod or tie	lighter	1.77x heavier
Strong beam	lighter	34% heavier
Strong panel or plate	lighter	17% 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 PLA or Rubber?

Rubber stretches further before it breaks: 830% elongation at break against 7.8% for Plastic PLA.

Thermal

Which conducts heat better, Plastic PLA or Rubber?

Rubber conducts heat better: 0.151 W/m·K against 0.13 W/m·K for Plastic PLA.