BASF Ultradur B 4300 G6 (PBT, 30% glass fibre), injection moulding grade; product information sheet 09/2026, typical values for uncoloured product at 23 °C.
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 PBT GF30 stronger than Steel AISI 4340?
Steel AISI 4340 is stronger: its yield strength is 1,035 MPa against tensile strength 140 MPa for Plastic PBT GF30 (7.39x).
Which is lighter, Plastic PBT GF30 or Steel AISI 4340?
Plastic PBT GF30 is lighter: 1,530 kg/m³ against 7,840 kg/m³ for Steel AISI 4340.
Which is stiffer, Plastic PBT GF30 or Steel AISI 4340?
Steel AISI 4340 is stiffer: Young's modulus 200 GPa against 9.8 GPa for Plastic PBT GF30, so the same part in Steel AISI 4340 deflects less under the same load.
Which is lighter for the same job, Plastic PBT GF30 or Steel AISI 4340?
For the same stiffness or strength: Plastic PBT GF30 is lighter for a stiff beam (bending), stiff panel or plate, strong beam, strong panel or plate; Steel AISI 4340 is lighter for a stiff rod or tie (tension), strong rod or tie.
Part that must be
Plastic PBT GF30
Steel AISI 4340
Stiff rod or tie (tension)
3.98x heavier
lighter
Stiff beam (bending)
lighter
13% heavier
Stiff panel or plate
lighter
1.88x heavier
Strong rod or tie
44% heavier
lighter
Strong beam
lighter
35% 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).
Which conducts heat better, Plastic PBT GF30 or Steel AISI 4340?
Steel AISI 4340 conducts heat better: 37.5 W/m·K against 0.27 W/m·K for Plastic PBT GF30.
Which expands less with temperature?
Steel AISI 4340 expands less: 11.3 µm/m·K against 25 µm/m·K for Plastic PBT GF30.