1100-O (annealed) commercially pure aluminium, Kaiser Aluminum Tube & Pipe Alloy 1100 Technical Data (Rev. 05/06), typical properties; specific heat from Hydro EN AW-1050A (99.5% Al) extruded-products datasheet (10/2018).
DuPont Delrin 100 acetal homopolymer, Table 2 'Typical Properties of Delrin Acetal Resins' (ASTM methods), Delrin Design Guide Module III hosted on delrin.com
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 Aluminum 1100-O stronger than Plastic POM/Acetal?
Plastic POM/Acetal is stronger: its yield strength is 69 MPa against 35 MPa for Aluminum 1100-O (1.97x).
Which is lighter, Aluminum 1100-O or Plastic POM/Acetal?
Plastic POM/Acetal is lighter: 1,420 kg/m³ against 2,710 kg/m³ for Aluminum 1100-O.
Which is stiffer, Aluminum 1100-O or Plastic POM/Acetal?
Aluminum 1100-O is stiffer: Young's modulus 69 GPa against 2.8 GPa for Plastic POM/Acetal, so the same part in Aluminum 1100-O deflects less under the same load.
Which is lighter for the same job, Aluminum 1100-O or Plastic POM/Acetal?
For the same stiffness or strength: Aluminum 1100-O is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Plastic POM/Acetal is lighter for a strong rod or tie, strong beam, strong panel or plate.
Part that must be
Aluminum 1100-O
Plastic POM/Acetal
Stiff rod or tie (tension)
lighter
12.9x heavier
Stiff beam (bending)
lighter
2.6x heavier
Stiff panel or plate
lighter
1.52x heavier
Strong rod or tie
3.76x heavier
lighter
Strong beam
3x heavier
lighter
Strong panel or plate
2.68x 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, Aluminum 1100-O or Plastic POM/Acetal?
Aluminum 1100-O conducts heat better: 222 W/m·K against 0.4 W/m·K for Plastic POM/Acetal.
Which expands less with temperature?
Aluminum 1100-O expands less: 23.6 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.