Plastic PMMA vs. Stainless 17-4PH

Compare Plastic PMMA vs. Stainless 17-4PH strength, stiffness, weight and thermal properties.

Change either side

Plastic PMMABulk polymer (molded or machined)

Mechanical
Try it on a partA bracket to run stress or thermal on, free in your browser	Open in LessCAD	Open in LessCAD
Yield strength	not given (tensile used)	1,275MPasourcetypical, transverse, sheet/strip
Ultimate tensile strength	80MPasourcetypical, 23 °C	1,379MPasourcetypical, transverse, sheet/strip
Compressive strength	110MPasourcecompressive yield stress, typical	not sourced
Flexural strength	115MPasourcetypical	not sourced
Elongation at break	5.5%sourcetypical	9%sourcetypical, transverse, in 2 in. (50.8 mm)
Young's modulus (stiffness)	3.3GPasourcetypical, short-term	197GPasourceH 900
Density	1,190kg/m³sourcetypical	7,800kg/m³sourceH 900
Strength to weight	67.2kN·m/kg	163kN·m/kg2.43x higher
Stiffness to weight	2.77MN·m/kg	25.3MN·m/kg9.11x higher
Poisson's ratio	0.37sourcetypical	0.272sourceH 900 (column)
Shear modulus	1.2GPa	77.4GPa64.3x stiffer in shear
Bulk modulus	4.23GPa	144GPa
Speed of sound	1,665m/s	5,026m/s
Thermal
Thermal conductivity	0.19W/m·Ksourcetypical	17.9W/m·Ksourceat 149 °C (300 °F), H 900
Thermal expansion	70µm/m·Ksource0-50 °C	10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900
100 mm part over a 50 °C swing	350µm growth	54µm growth6.48x less
Specific heat	1,470J/kg·Ksourcetypical	460J/kg·Ksourcemean, 0–100 °C, H 900
Heats up and cools (diffusivity)	0.109mm²/s	4.99mm²/s45.9x faster
Thermal shock resistance	41.5W/m	7,809W/m188x more resistant
Max service temperature	80°Csourcemax. permanent service temperature	316°Csourcestrength-retention limit (not oxidation)
Values for	Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1)	Cleveland-Cliffs 17-4 PH, Condition H 900, sheet/strip, transverse (Product Data Bulletin, May 2021)

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 Stainless 17-4PH?

Stainless 17-4PH is stronger: its yield strength is 1,275 MPa against tensile strength 80 MPa for Plastic PMMA (15.9x).

Which is lighter, Plastic PMMA or Stainless 17-4PH?

Plastic PMMA is lighter: 1,190 kg/m³ against 7,800 kg/m³ for Stainless 17-4PH.

Which is stiffer, Plastic PMMA or Stainless 17-4PH?

Stainless 17-4PH is stiffer: Young's modulus 197 GPa against 3.3 GPa for Plastic PMMA, so the same part in Stainless 17-4PH deflects less under the same load.

Which is lighter for the same job, Plastic PMMA or Stainless 17-4PH?

For the same stiffness or strength: Plastic PMMA is lighter for a stiff panel or plate, strong beam, strong panel or plate; Stainless 17-4PH is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.

Part that must be	Plastic PMMA	Stainless 17-4PH
Stiff rod or tie (tension)	9.11x heavier	lighter
Stiff beam (bending)	18% heavier	lighter
Stiff panel or plate	lighter	1.68x heavier
Strong rod or tie	2.43x heavier	lighter
Strong beam	lighter	3% heavier
Strong panel or plate	lighter	1.64x 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 Stainless 17-4PH?

Stainless 17-4PH conducts heat better: 17.9 W/m·K against 0.19 W/m·K for Plastic PMMA.

Which expands less with temperature?

Stainless 17-4PH expands less: 10.8 µm/m·K against 70 µm/m·K for Plastic PMMA.

Among 59 materials

Stiffness against density

Strength against density