Plastic UHMWPE vs. Silicon

Compare Plastic UHMWPE vs. Silicon strength, stiffness, weight and thermal properties.

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Plastic UHMWPEBulk polymer (molded or machined)

SiliconGrown single crystal

Mechanical
Try it on a partA sample part to run stress or thermal on, free in your browser	Open in LessCAD	Open in LessCAD
Yield strength	20MPasourcetypical, tensile stress at yield ISO 527, 50 mm/min	not given (tensile used)
Ultimate tensile strength	43MPasourcetypical, tensile stress at break ISO 527, 50 mm/min	130MPasourcemodulus of rupture (bending fracture stress); brittle, no yield point
Flexural strength	not sourced	130MPasourcemodulus of rupture
Elongation at break	465%sourcetypical, nominal elongation at break ISO 527	not sourced
Young's modulus (stiffness)	0.66GPasourcetypical, tensile modulus ISO 527, 1 mm/min	131GPasourcetypical (single quoted value of an anisotropic crystal)
Density	930kg/m³sourcetypical2.5x lighter	2,329kg/m³sourcetypical
Strength to weight	21.5kN·m/kg	55.8kN·m/kg2.6x higher
Stiffness to weight	0.71MN·m/kg	56.2MN·m/kg79.3x higher
Poisson's ratio	not sourced	0.221sourcetypical
Shear modulus	not sourced	53.6GPa
Bulk modulus	not sourced	78.3GPa
Speed of sound	842m/s	7,500m/s
Thermal
Thermal conductivity	0.4W/m·Ksourcetypical, unfilled (narrative value, generic Celanese UHMWPE)	163W/m·Ksourcetypical at 313 K (40 °C)
Thermal expansion	200µm/m·Ksourcetypical, 20 to 100 °C (generic Celanese UHMWPE)	2.62µm/m·Ksourcetypical at 300 K
100 mm part over a 50 °C swing	1,000µm growth	13.1µm growth76.3x less
Specific heat	not sourced	732J/kg·Ksourcetypical
Heats up and cools (diffusivity)	not sourced	95.6mm²/s
Thermal shock resistance	not sourced	48,095W/m
Melting point	130–138°CsourceDSC 10 K/min	1,412°Csourcetypical
Max service temperature	80°Csourcerecommended max constant operating temperature	300°Csourceproducer's maximum application temperature (optical components)
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)	Synthetic single-crystal silicon (cubic, diamond structure), Korth Kristalle (crystal grower) material data; Korth usually supplies Floating Zone (FZ) material, Czochralski (Cz) also offered. Silicon is elastically anisotropic; the producer quotes one modulus and the solver is isotropic.

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 Silicon?

Silicon is stronger: its tensile strength is 130 MPa against yield strength 20 MPa for Plastic UHMWPE (6.5x).

Which is lighter, Plastic UHMWPE or Silicon?

Plastic UHMWPE is lighter: 930 kg/m³ against 2,329 kg/m³ for Silicon.

Which is stiffer, Plastic UHMWPE or Silicon?

Silicon is stiffer: Young's modulus 131 GPa against 0.66 GPa for Plastic UHMWPE, so the same part in Silicon deflects less under the same load.

Which is lighter for the same job, Plastic UHMWPE or Silicon?

For the same stiffness or strength: Silicon is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.

Part that must be	Plastic UHMWPE	Silicon
Stiff rod or tie (tension)	79.3x heavier	lighter
Stiff beam (bending)	5.63x heavier	lighter
Stiff panel or plate	2.33x heavier	lighter
Strong rod or tie	2.6x heavier	lighter
Strong beam	39% heavier	lighter
Strong panel or plate	2% 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).

Which conducts heat better, Plastic UHMWPE or Silicon?

Silicon conducts heat better: 163 W/m·K against 0.4 W/m·K for Plastic UHMWPE.

Which expands less with temperature?

Silicon expands less: 2.62 µm/m·K against 200 µm/m·K for Plastic UHMWPE.

Among 72 materials

Stiffness against density

Strength against density