Plastic Polypropylene vs. Titanium Ti-6Al-4V

Compare Plastic Polypropylene vs. Titanium Ti-6Al-4V strength, stiffness, weight and thermal properties.

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Plastic PolypropyleneBulk polymer (molded or machined)

Mechanical
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Yield strength	33MPasourcetypical, tensile stress at yield ISO 527	885MPasourcetypical, plate (>0.187 in), annealed, 0.2% offset
Ultimate tensile strength	not sourced	940MPasourcetypical, plate, annealed
Elongation at break	not sourced	16%sourcetypical, in 2 in., plate annealed
Young's modulus (stiffness)	1.45GPasourcetypical, tensile modulus ISO 527	107–122GPasourcetypical range, 20 °C
Density	900kg/m³sourcetypical, 23 °C ISO 1183-1	4,430kg/m³sourcenominal
Strength to weight	36.7kN·m/kg	200kN·m/kg5.45x higher
Stiffness to weight	1.61MN·m/kg	25.8MN·m/kg16x higher
Poisson's ratio	0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	0.342sourcemean of TIMET measurements
Shear modulus	0.511GPa	42.7GPa83.6x stiffer in shear
Bulk modulus	3.02GPa	121GPa
Speed of sound	1,269m/s	5,084m/s
Thermal
Thermal conductivity	0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	6.6W/m·Ksourcetypical, 20 °C, mill annealed
Thermal expansion	80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	9µm/m·Ksourcetypical, mean 0-100 °C
100 mm part over a 50 °C swing	450µm growth	45µm growth10x less
Specific heat	not sourced	580J/kg·Ksourcetypical, 20 °C
Heats up and cools (diffusivity)	not sourced	2.57mm²/s
Thermal shock resistance	28.6W/m	3,730W/m130x more resistant
Melting point	not sourced	1,630–1,650°Csourcemelting range
Max service temperature	90°CsourceHDT 0.45 MPa (ISO 75B), unannealed	400°Csourceupper recommended use temperature
Values for	LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values	TIMETAL 6-4 (Ti-6Al-4V Grade 5) annealed plate typical (TIMET properties manual) + TIMET datasheet TMC-0150 physical properties

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 Polypropylene stronger than Titanium Ti-6Al-4V?

Titanium Ti-6Al-4V is stronger: its yield strength is 885 MPa against 33 MPa for Plastic Polypropylene (26.8x).

Which is lighter, Plastic Polypropylene or Titanium Ti-6Al-4V?

Plastic Polypropylene is lighter: 900 kg/m³ against 4,430 kg/m³ for Titanium Ti-6Al-4V.

Which is stiffer, Plastic Polypropylene or Titanium Ti-6Al-4V?

Titanium Ti-6Al-4V is stiffer: Young's modulus 115 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Titanium Ti-6Al-4V deflects less under the same load.

Which is lighter for the same job, Plastic Polypropylene or Titanium Ti-6Al-4V?

For the same stiffness or strength: Plastic Polypropylene is lighter for a stiff panel or plate; Titanium Ti-6Al-4V is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam, strong panel or plate.

Part that must be	Plastic Polypropylene	Titanium Ti-6Al-4V
Stiff rod or tie (tension)	16x heavier	lighter
Stiff beam (bending)	1.81x heavier	lighter
Stiff panel or plate	lighter	15% heavier
Strong rod or tie	5.45x heavier	lighter
Strong beam	1.82x heavier	lighter
Strong panel or plate	5% 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 Polypropylene or Titanium Ti-6Al-4V?

Titanium Ti-6Al-4V conducts heat better: 6.6 W/m·K against 0.195 W/m·K for Plastic Polypropylene.

Which expands less with temperature?

Titanium Ti-6Al-4V expands less: 9 µm/m·K against 90 µm/m·K for Plastic Polypropylene.

Among 59 materials

Stiffness against density

Strength against density