Plastic Nylon PA66 vs. Plastic Polypropylene

Compare Plastic Nylon PA66 vs. Plastic Polypropylene strength, stiffness, weight and thermal properties.

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Plastic Nylon PA66Bulk polymer (molded or machined)

Plastic PolypropyleneBulk polymer (molded or machined)

Mechanical
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Yield strength	85MPasourcetypical, dry	33MPasourcetypical, tensile stress at yield ISO 527
Ultimate tensile strength	not sourced	not sourced
Elongation at break	30%sourcenominal strain at break, dry	not sourced
Young's modulus (stiffness)	3GPasourcetypical, dry	1.45GPasourcetypical, tensile modulus ISO 527
Density	1,130kg/m³sourcetypical	900kg/m³sourcetypical, 23 °C ISO 1183-1
Strength to weight	75.2kN·m/kg2.05x higher	36.7kN·m/kg
Stiffness to weight	2.65MN·m/kg1.65x higher	1.61MN·m/kg
Poisson's ratio	0.4sourcebase material: unfilled polyamide (PA), conditioned, maker design-guide family value (Covestro Table 3-1)	0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)
Shear modulus	1.07GPa2.1x stiffer in shear	0.511GPa
Bulk modulus	5GPa	3.02GPa
Speed of sound	1,629m/s	1,269m/s
Thermal
Thermal conductivity	0.33W/m·Ksourcetypical	0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)
Thermal expansion	98µm/m·Ksourcelongitudinal, 23-55 °C	80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)
100 mm part over a 50 °C swing	490µm growth	450µm growth9% less
Specific heat	1,700J/kg·Ksourcetypical	not sourced
Heats up and cools (diffusivity)	0.172mm²/s	not sourced
Thermal shock resistance	57.2W/m2x more resistant	28.6W/m
Melting point	260°CsourceDSC	not sourced
Max service temperature	101°CsourceIEC 60216 temperature index, 20000 h	90°CsourceHDT 0.45 MPa (ISO 75B), unannealed
Values for	BASF Ultramid A3K (PA66, unreinforced injection-moulding grade), Product Information 02/2026, dry values (ISO methods)	LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO 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 Nylon PA66 stronger than Plastic Polypropylene?

Plastic Nylon PA66 is stronger: its yield strength is 85 MPa against 33 MPa for Plastic Polypropylene (2.58x).

Which is lighter, Plastic Nylon PA66 or Plastic Polypropylene?

Plastic Polypropylene is lighter: 900 kg/m³ against 1,130 kg/m³ for Plastic Nylon PA66.

Which is stiffer, Plastic Nylon PA66 or Plastic Polypropylene?

Plastic Nylon PA66 is stiffer: Young's modulus 3 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in Plastic Nylon PA66 deflects less under the same load.

Which is lighter for the same job, Plastic Nylon PA66 or Plastic Polypropylene?

For the same stiffness or strength: Plastic Nylon PA66 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 Nylon PA66	Plastic Polypropylene
Stiff rod or tie (tension)	lighter	1.65x heavier
Stiff beam (bending)	lighter	15% heavier
Stiff panel or plate	lighter	1% heavier
Strong rod or tie	lighter	2.05x heavier
Strong beam	lighter	50% heavier
Strong panel or plate	lighter	28% 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 Nylon PA66 or Plastic Polypropylene?

Plastic Nylon PA66 conducts heat better: 0.33 W/m·K against 0.195 W/m·K for Plastic Polypropylene.

Which expands less with temperature?

Plastic Polypropylene expands less: 90 µm/m·K against 98 µm/m·K for Plastic Nylon PA66.

Among 59 materials

Stiffness against density

Strength against density