Plastic Polycarbonate vs. Rubber

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

Plastic PolycarbonateBulk polymer (molded or machined)

RubberBulk polymer (molded or machined)

Mechanical	Plastic Polycarbonate	Rubber
Yield strength	65MPa1	not given (tensile used)
Ultimate tensile strength	65MPa1	23MPa2
Flexural strength	97MPa1	not sourced
Elongation at break	125%1	830%26.64x more ductile
Young's modulus (stiffness)	2.4GPa1	not sourced
Density	1,200kg/m³1	960kg/m³225% lighter
Strength to weight	54.2kN·m/kg2.26x higher	24kN·m/kg
Stiffness to weight	2MN·m/kg	not sourced
Poisson's ratio	0.383	government0.54
Shear modulus	0.87GPa	not sourced
Bulk modulus	3.33GPa	not sourced
Speed of sound	1,414m/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 Polycarbonate	Rubber
Thermal conductivity	0.2W/m·K132% more heat through a fin	0.151W/m·K5
Thermal expansion	65µm/m·K1	not sourced
100 mm part over a 50 °C swing	325µm growth	not sourced
Specific heat	1,172J/kg·K6	government1,881J/kg·K41.6x higher
Heats up and cools (diffusivity)	0.142mm²/s1.7x faster	0.0836mm²/s
Thermal shock resistance	51.7W/m	not sourced
Glass transition	144°C1	not sourced
Max service temperature	UL 746B RTI125°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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Sources6 documents: Covestro, Weir Minerals, National Institute of Standards and Technology, Defense Technical Information Center, Bayer MaterialScience

Plastic Polycarbonate: Covestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical values
Rubber: Weir Minerals Linatex Premium rubber (95 % natural rubber), typical physical properties, spec sheet WMD0118/202305

1
Makrolon 2405 Technical Data SheetCovestroPlastic Polycarbonate · Yield strength: typical, tensile yieldPlastic Polycarbonate · Ultimate tensile strength: typical, stress at breakPlastic Polycarbonate · Flexural strength: typical, flexural strengthPlastic Polycarbonate · Elongation at break: typical, strain at breakPlastic Polycarbonate · Young's modulus (stiffness): typicalPlastic Polycarbonate · Density: typicalPlastic Polycarbonate · Thermal conductivity: typical, through-plane, 23 CPlastic Polycarbonate · Thermal expansion: typical, 23-55 C, parallel and normalPlastic Polycarbonate · Glass transition: typical, DSC 10 C/minPlastic Polycarbonate · Max service temperature: UL 746B RTI, tensile strength, 1.5 mm
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
Engineering Polymers Part and Mold Design: Thermoplastics, A Design GuideCovestroarchived copyPlastic Polycarbonate · Poisson's ratio: typical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1)
4
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
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
6
Makrolon 2405 Data Sheet, ASTM valuesBayer MaterialSciencearchived copyPlastic Polycarbonate · Specific heat: typical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766

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 Polycarbonate stronger than Rubber?

Plastic Polycarbonate is stronger: its yield strength is 65 MPa against tensile strength 23 MPa for Rubber (2.83x).

Which is lighter, Plastic Polycarbonate or Rubber?

Rubber is lighter: 960 kg/m³ against 1,200 kg/m³ for Plastic Polycarbonate.

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

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

Part that must be	Plastic Polycarbonate	Rubber
Strong rod or tie	lighter	2.26x heavier
Strong beam	lighter	1.6x heavier
Strong panel or plate	lighter	34% 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 Polycarbonate or Rubber?

Rubber stretches further before it breaks: 830% elongation at break against 125% for Plastic Polycarbonate.

Thermal

Which conducts heat better, Plastic Polycarbonate or Rubber?

Plastic Polycarbonate conducts heat better: 0.2 W/m·K against 0.151 W/m·K for Rubber.