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

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

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Plastic PMMABulk polymer (molded or machined)

Mechanical
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Yield strength	not given (tensile used)	885MPasourcetypical, plate (>0.187 in), annealed, 0.2% offset
Ultimate tensile strength	80MPasourcetypical, 23 °C	940MPasourcetypical, plate, annealed
Compressive strength	110MPasourcecompressive yield stress, typical	not sourced
Flexural strength	115MPasourcetypical	not sourced
Elongation at break	5.5%sourcetypical	16%sourcetypical, in 2 in., plate annealed
Young's modulus (stiffness)	3.3GPasourcetypical, short-term	107–122GPasourcetypical range, 20 °C
Density	1,190kg/m³sourcetypical	4,430kg/m³sourcenominal
Strength to weight	67.2kN·m/kg	200kN·m/kg2.97x higher
Stiffness to weight	2.77MN·m/kg	25.8MN·m/kg9.32x higher
Poisson's ratio	0.37sourcetypical	0.342sourcemean of TIMET measurements
Shear modulus	1.2GPa	42.7GPa35.4x stiffer in shear
Bulk modulus	4.23GPa	121GPa
Speed of sound	1,665m/s	5,084m/s
Thermal
Thermal conductivity	0.19W/m·Ksourcetypical	6.6W/m·Ksourcetypical, 20 °C, mill annealed
Thermal expansion	70µm/m·Ksource0-50 °C	9µm/m·Ksourcetypical, mean 0-100 °C
100 mm part over a 50 °C swing	350µm growth	45µm growth7.78x less
Specific heat	1,470J/kg·Ksourcetypical	580J/kg·Ksourcetypical, 20 °C
Heats up and cools (diffusivity)	0.109mm²/s	2.57mm²/s23.6x faster
Thermal shock resistance	41.5W/m	3,730W/m90x more resistant
Melting point	not sourced	1,630–1,650°Csourcemelting range
Max service temperature	80°Csourcemax. permanent service temperature	400°Csourceupper recommended use temperature
Values for	Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1)	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 PMMA stronger than Titanium Ti-6Al-4V?

Titanium Ti-6Al-4V is stronger: its yield strength is 885 MPa against tensile strength 80 MPa for Plastic PMMA (11.1x).

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

Plastic PMMA is lighter: 1,190 kg/m³ against 4,430 kg/m³ for Titanium Ti-6Al-4V.

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

Titanium Ti-6Al-4V is stiffer: Young's modulus 115 GPa against 3.3 GPa for Plastic PMMA, so the same part in Titanium Ti-6Al-4V deflects less under the same load.

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

For the same stiffness or strength: Plastic PMMA is lighter for a stiff panel or plate, strong 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.

Part that must be	Plastic PMMA	Titanium Ti-6Al-4V
Stiff rod or tie (tension)	9.32x heavier	lighter
Stiff beam (bending)	1.58x heavier	lighter
Stiff panel or plate	lighter	14% heavier
Strong rod or tie	2.97x heavier	lighter
Strong beam	33% heavier	lighter
Strong panel or plate	lighter	12% 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 conducts heat better, Plastic PMMA or Titanium Ti-6Al-4V?

Titanium Ti-6Al-4V conducts heat better: 6.6 W/m·K against 0.19 W/m·K for Plastic PMMA.

Which expands less with temperature?

Titanium Ti-6Al-4V expands less: 9 µm/m·K against 70 µm/m·K for Plastic PMMA.

Among 59 materials

Stiffness against density

Strength against density