Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1)
Ultimaker TPU 95A, 3D-printed specimens, XY (flat); Ultimaker S5 Pro, engineering intent profile, 0.15 mm layer height, AA 0.4 print core, 100% infill, Cura 4.9, printed one-at-a-time, conditioned >=24 h at room temperature. TDS (file v5.00), April 29, 2022.
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.
Plastic TPU is 3D printed: its properties depend on build direction and print settings; these are typical values.
Questions
Is Plastic PMMA stronger than Plastic TPU?
Plastic PMMA is stronger: its tensile strength is 80 MPa against 23.7 MPa for Plastic TPU (3.38x).
Which is lighter, Plastic PMMA or Plastic TPU?
Plastic PMMA is lighter: 1,190 kg/m³ against 1,220 kg/m³ for Plastic TPU.
Which is stiffer, Plastic PMMA or Plastic TPU?
Plastic PMMA is stiffer: Young's modulus 3.3 GPa against 0.067 GPa for Plastic TPU, so the same part in Plastic PMMA deflects less under the same load.
Which is lighter for the same job, Plastic PMMA or Plastic TPU?
For the same stiffness or strength: Plastic PMMA 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 PMMA
Plastic TPU
Stiff rod or tie (tension)
lighter
50.5x heavier
Stiff beam (bending)
lighter
7.2x heavier
Stiff panel or plate
lighter
3.76x heavier
Strong rod or tie
lighter
3.46x heavier
Strong beam
lighter
2.31x heavier
Strong panel or plate
lighter
1.88x 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).