Plastic Polycarbonate vs. Plastic POM/Acetal

Compare Plastic Polycarbonate vs. Plastic POM/Acetal strength, stiffness, weight and thermal properties.

Plastic PolycarbonateBulk polymer (molded or machined)

Plastic POM/AcetalBulk polymer (molded or machined)

Mechanical	Plastic Polycarbonate	Plastic POM/Acetal
Yield strength	65MPa1	69MPa2
Ultimate tensile strength	65MPa1	69MPa2
Compressive strength	not sourced	124MPa2
Flexural strength	97MPa1	99MPa2
Elongation at break	125%11.67x more ductile	75%2
Young's modulus (stiffness)	2.4GPa1	2.8GPa217% stiffer
Density	1,200kg/m³118% lighter	1,420kg/m³3
Strength to weight	54.2kN·m/kg11% higher	48.6kN·m/kg
Stiffness to weight	2MN·m/kg1% higher	1.97MN·m/kg
Poisson's ratio	0.384	0.352
Shear modulus	0.87GPa	1.04GPa19% stiffer in shear
Bulk modulus	3.33GPa7% higher	3.11GPa
Speed of sound	1,414m/s	1,404m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Plastic Polycarbonate	Plastic POM/Acetal
Thermal conductivity	0.2W/m·K1	0.4W/m·K22x more heat through a fin
Thermal expansion	65µm/m·K11.88x less	mean122µm/m·K2
100 mm part over a 50 °C swing	325µm growth1.88x less	610µm growth
Specific heat	1,172J/kg·K5	average -18 to 100 °C1,465J/kg·K225% higher
Heats up and cools (diffusivity)	0.142mm²/s	0.192mm²/s35% faster
Thermal shock resistance	51.7W/m	52.5W/m2% more resistant
Melting point	not sourced	175°C2
Glass transition	144°C1	not sourced
Max service temperature	UL 746B RTI125°C1	HDT 1.8 MPa125°C2

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources5 documents: Covestro, DuPont, Bayer MaterialScience

Plastic Polycarbonate: Covestro Makrolon 2405 general-purpose PC (MVR 19), Covestro technical datasheet version 2026-09-28, typical values
Plastic POM/Acetal: DuPont Delrin 100 acetal homopolymer, Table 2 'Typical Properties of Delrin Acetal Resins' (ASTM methods), Delrin Design Guide Module III hosted on delrin.com

1
Makrolon 2405 Technical Data SheetCovestroPlastic Polycarbonate · Yield strength: typical, tensile yieldPlastic Polycarbonate · Ultimate tensile strength: typical, stress at breakPlastic Polycarbonate · Flexural strength: typical, flexural strengthPlastic Polycarbonate · Elongation at break: typical, strain at breakPlastic Polycarbonate · Young's modulus (stiffness): typicalPlastic Polycarbonate · Density: typicalPlastic Polycarbonate · Thermal conductivity: typical, through-plane, 23 CPlastic Polycarbonate · Thermal expansion: typical, 23-55 C, parallel and normalPlastic Polycarbonate · Glass transition: typical, DSC 10 C/minPlastic Polycarbonate · Max service temperature: UL 746B RTI, tensile strength, 1.5 mm
2
Delrin Acetal Resin Design Guide, Module IIIDuPontarchived copyPlastic POM/Acetal · Yield strength: typical (single ASTM D638 tensile strength)Plastic POM/Acetal · Ultimate tensile strength: typicalPlastic POM/Acetal · Compressive strength: compressive stress at 10% deformationPlastic POM/Acetal · Flexural strength: flexural yield strength, typicalPlastic POM/Acetal · Elongation at break: typicalPlastic POM/Acetal · Young's modulus (stiffness): typicalPlastic POM/Acetal · Poisson's ratio: typicalPlastic POM/Acetal · Thermal conductivity: typicalPlastic POM/Acetal · Thermal expansion: mean, 29 to 60 °CPlastic POM/Acetal · Specific heat: average -18 to 100 °C, Delrin acetal resins (not grade-specific)Plastic POM/Acetal · Melting point: crystalline melting pointPlastic POM/Acetal · Max service temperature: HDT 1.8 MPa (annealed)
3
Delrin 100 Product Data SheetDuPontPlastic POM/Acetal · Density: typical (DuPont product information for Delrin 100 NC010; 'The data listed here fall within the normal range of product properties')
4
Engineering Polymers Part and Mold Design: Thermoplastics, A Design GuideCovestroarchived copyPlastic Polycarbonate · Poisson's ratio: typical, polycarbonate family (Covestro Part and Mold Design guide, Table 3-1)
5
Makrolon 2405 Data Sheet, ASTM valuesBayer MaterialSciencearchived copyPlastic Polycarbonate · Specific heat: typical (guide value), Bayer ASTM datasheet for Makrolon 2405, ASTM D 2766

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Mechanical

Is Plastic Polycarbonate stronger than Plastic POM/Acetal?

Plastic POM/Acetal is stronger: its yield strength is 69 MPa against 65 MPa for Plastic Polycarbonate (6%).

Which is lighter, Plastic Polycarbonate or Plastic POM/Acetal?

Plastic Polycarbonate is lighter: 1,200 kg/m³ against 1,420 kg/m³ for Plastic POM/Acetal.

Which is stiffer, Plastic Polycarbonate or Plastic POM/Acetal?

Plastic POM/Acetal is stiffer: Young's modulus 2.8 GPa against 2.4 GPa for Plastic Polycarbonate, so the same part in Plastic POM/Acetal deflects less under the same load.

Which is lighter for the same job, Plastic Polycarbonate or Plastic POM/Acetal?

For the same stiffness or strength: Plastic Polycarbonate 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 Polycarbonate	Plastic POM/Acetal
Stiff rod or tie (tension)	lighter	1% heavier
Stiff beam (bending)	lighter	10% heavier
Stiff panel or plate	lighter	12% heavier
Strong rod or tie	lighter	11% heavier
Strong beam	lighter	14% heavier
Strong panel or plate	lighter	15% 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 is more ductile, Plastic Polycarbonate or Plastic POM/Acetal?

Plastic Polycarbonate stretches further before it breaks: 125% elongation at break against 75% for Plastic POM/Acetal.

Thermal

Which conducts heat better, Plastic Polycarbonate or Plastic POM/Acetal?

Plastic POM/Acetal conducts heat better: 0.4 W/m·K against 0.2 W/m·K for Plastic Polycarbonate.

Which expands less with temperature?

Plastic Polycarbonate expands less: 65 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.