Plastic PBT GF30 vs. Zinc Zamak 3

Compare Plastic PBT GF30 vs. Zinc Zamak 3 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)	221MPasourcetypical
Ultimate tensile strength	140MPasourcestress at break, 23 °C	283MPasourcetypical
Flexural strength	210MPasourcetypical, 23 °C	not sourced
Elongation at break	3%sourcestrain at break, 23 °C	10%sourcetypical, in 2 in.
Young's modulus (stiffness)	9.8GPasourcetypical, 23 °C	85.5GPasourcetypical
Density	1,530kg/m³sourcetypical4.31x lighter	6,600kg/m³sourcetypical
Strength to weight	91.5kN·m/kg2.73x higher	33.5kN·m/kg
Stiffness to weight	6.41MN·m/kg	13MN·m/kg2.02x higher
Poisson's ratio	not sourced	0.27sourcetypical, Zamak 3 hot-chamber die cast
Shear modulus	not sourced	33.7GPa
Bulk modulus	not sourced	62GPa
Speed of sound	2,531m/s	3,599m/s
Thermal
Thermal conductivity	0.27W/m·Ksourcetypical (DIN 52612-1)	113W/m·Ksourcetypical
Thermal expansion	25µm/m·Ksourcelongitudinal (flow), mean 23-55 °C	27.4µm/m·Ksourcetypical
100 mm part over a 50 °C swing	125µm growth10% less	137µm growth
Specific heat	1,050J/kg·Ksourcetypical, 23 °C	419J/kg·Ksourcetypical
Heats up and cools (diffusivity)	0.168mm²/s	40.9mm²/s243x faster
Thermal shock resistance	not sourced	7,782W/m
Melting point	223°CsourceDSC (ISO 11357)	381–387°Csourcemelting range
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.	Zamak 3 (ASTM B86 die cast), Nathan Trotter (zinc alloy producer) technical data sheet, typical values

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 Zinc Zamak 3?

Zinc Zamak 3 is stronger: its yield strength is 221 MPa against tensile strength 140 MPa for Plastic PBT GF30 (1.58x).

Which is lighter, Plastic PBT GF30 or Zinc Zamak 3?

Plastic PBT GF30 is lighter: 1,530 kg/m³ against 6,600 kg/m³ for Zinc Zamak 3.

Which is stiffer, Plastic PBT GF30 or Zinc Zamak 3?

Zinc Zamak 3 is stiffer: Young's modulus 85.5 GPa against 9.8 GPa for Plastic PBT GF30, so the same part in Zinc Zamak 3 deflects less under the same load.

Which is lighter for the same job, Plastic PBT GF30 or Zinc Zamak 3?

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; Zinc Zamak 3 is lighter for a stiff rod or tie (tension).

Part that must be	Plastic PBT GF30	Zinc Zamak 3
Stiff rod or tie (tension)	2.02x heavier	lighter
Stiff beam (bending)	lighter	46% heavier
Stiff panel or plate	lighter	2.1x heavier
Strong rod or tie	lighter	2.73x heavier
Strong beam	lighter	3.18x heavier
Strong panel or plate	lighter	3.43x 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 Zinc Zamak 3?

Zinc Zamak 3 conducts heat better: 113 W/m·K against 0.27 W/m·K for Plastic PBT GF30.

Which expands less with temperature?

Plastic PBT GF30 expands less: 25 µm/m·K against 27.4 µm/m·K for Zinc Zamak 3.

Among 72 materials

Stiffness against density

Strength against density