Plastic PBT GF30 vs. Steel AISI 1045

Compare Plastic PBT GF30 vs. Steel AISI 1045 strength, stiffness, weight and thermal properties.

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Plastic PBT GF30Bulk polymer (molded or machined)

Mechanical
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Yield strength	not given (tensile used)	531MPasourceproducer-stated, cold drawn
Ultimate tensile strength	140MPasourcestress at break, 23 °C	627MPasourceproducer-stated, cold drawn
Flexural strength	210MPasourcetypical, 23 °C	not sourced
Elongation at break	3%sourcestrain at break, 23 °C	12%sourcein 2 in (50.8 mm)
Young's modulus (stiffness)	9.8GPasourcetypical, 23 °C	210GPasourcetypical
Density	1,530kg/m³sourcetypical5.1x lighter	7,800kg/m³sourcetypical
Strength to weight	91.5kN·m/kg34% higher	68.1kN·m/kg
Stiffness to weight	6.41MN·m/kg	26.9MN·m/kg4.2x higher
Poisson's ratio	not sourced	0.3sourcetypical
Shear modulus	not sourced	80.8GPa
Bulk modulus	not sourced	175GPa
Speed of sound	2,531m/s	5,189m/s
Thermal
Thermal conductivity	0.27W/m·Ksourcetypical (DIN 52612-1)	40–45W/m·Ksourcetypical range, ambient
Thermal expansion	25µm/m·Ksourcelongitudinal (flow), mean 23-55 °C	12µm/m·Ksourcetypical, mean 20-300 °C
100 mm part over a 50 °C swing	125µm growth	60µm growth2.08x less
Specific heat	1,050J/kg·Ksourcetypical, 23 °C	460–480J/kg·Ksourcetypical range, 50/100 °C
Heats up and cools (diffusivity)	0.168mm²/s	11.6mm²/s69x faster
Thermal shock resistance	not sourced	6,269W/m
Melting point	223°CsourceDSC (ISO 11357)	not sourced
Max service temperature	205°CsourceHDT 1.8 MPa	not sourced
Values for	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.	AISI 1045 cold drawn bar (Niagara LaSalle) for mechanical; Ovako C45 (lists 'SAE 1045' as a similar designation) for physical constants

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 1045?

Steel AISI 1045 is stronger: its yield strength is 531 MPa against tensile strength 140 MPa for Plastic PBT GF30 (3.79x).

Which is lighter, Plastic PBT GF30 or Steel AISI 1045?

Plastic PBT GF30 is lighter: 1,530 kg/m³ against 7,800 kg/m³ for Steel AISI 1045.

Which is stiffer, Plastic PBT GF30 or Steel AISI 1045?

Steel AISI 1045 is stiffer: Young's modulus 210 GPa against 9.8 GPa for Plastic PBT GF30, so the same part in Steel AISI 1045 deflects less under the same load.

Which is lighter for the same job, Plastic PBT GF30 or Steel AISI 1045?

For the same stiffness or strength: Plastic PBT GF30 is lighter for a stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Steel AISI 1045 is lighter for a stiff rod or tie (tension).

Part that must be	Plastic PBT GF30	Steel AISI 1045
Stiff rod or tie (tension)	4.2x heavier	lighter
Stiff beam (bending)	lighter	10% heavier
Stiff panel or plate	lighter	1.84x heavier
Strong rod or tie	lighter	34% heavier
Strong beam	lighter	2.1x heavier
Strong panel or plate	lighter	2.62x 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 1045?

Steel AISI 1045 conducts heat better: 42.5 W/m·K against 0.27 W/m·K for Plastic PBT GF30.

Which expands less with temperature?

Steel AISI 1045 expands less: 12 µm/m·K against 25 µm/m·K for Plastic PBT GF30.

Among 72 materials

Stiffness against density

Strength against density