Plastic PETG vs. Plastic POM/Acetal

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

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Plastic POM/AcetalBulk polymer (molded or machined)

Mechanical
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Yield strength	46.2MPasourcetypical	69MPasourcetypical (single ASTM D638 tensile strength)
Ultimate tensile strength	46.2MPasourcetypical, peak stress (= stress at yield)	69MPasourcetypical
Compressive strength	not sourced	124MPasourcecompressive stress at 10% deformation
Flexural strength	78.9MPasourcetypical	99MPasourceflexural yield strength, typical
Elongation at break	7.6%sourcetypical	75%sourcetypical9.87x more ductile
Young's modulus (stiffness)	1.94GPasourcetypical	2.8GPasourcetypical44% stiffer
Density	1,270kg/m³sourcetypical	1,420kg/m³sourcetypical (DuPont product information for Delrin 100 NC010; 'The data listed here fall within the normal range of product properties')
Strength to weight	36.4kN·m/kg	48.6kN·m/kg34% higher
Stiffness to weight	1.53MN·m/kg	1.97MN·m/kg29% higher
Poisson's ratio	not sourced	0.35sourcetypical
Shear modulus	not sourced	1.04GPa
Bulk modulus	not sourced	3.11GPa
Speed of sound	1,236m/s	1,404m/s
Thermal
Thermal conductivity	0.21W/m·Ksourcebase material: Eastman Eastar Copolyester 6763 (PETG), typical	0.4W/m·Ksourcetypical
Thermal expansion	51µm/m·Ksourcebase material: Eastman Eastar Copolyester 6763 (PETG), typical	122µm/m·Ksourcemean, 29 to 60 °C
100 mm part over a 50 °C swing	255µm growth2.39x less	610µm growth
Specific heat	1,300J/kg·Ksourcebase material: Eastman Eastar Copolyester 6763 (PETG), DSC at 60 °C (lowest temperature listed)	1,465J/kg·Ksourceaverage -18 to 100 °C, Delrin acetal resins (not grade-specific)
Heats up and cools (diffusivity)	0.127mm²/s	0.192mm²/s1.51x faster
Thermal shock resistance	not sourced	52.5W/m
Melting point	not sourced	175°Csourcecrystalline melting point
Glass transition	77.4°Csourcetypical	not sourced
Max service temperature	76.2°CsourceHDT 0.455 MPa (printed specimens)	125°CsourceHDT 1.8 MPa (annealed)
Values for	Ultimaker PETG, 3D-printed specimens, XY (flat); Ultimaker S5 Pro, engineering intent profile, 0.15 mm layer height, AA 0.4 print core, 100% infill, Cura 4.9, printed one-at-a-time, conditioned >=24 h at room temperature. TDS v1.00, April 29, 2022.	DuPont Delrin 100 acetal homopolymer, Table 2 'Typical Properties of Delrin Acetal Resins' (ASTM methods), Delrin Design Guide Module III hosted on delrin.com

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.

Plastic PETG is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Is Plastic PETG stronger than Plastic POM/Acetal?

Plastic POM/Acetal is stronger: its yield strength is 69 MPa against 46.2 MPa for Plastic PETG (49%).

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

Plastic PETG is lighter: 1,270 kg/m³ against 1,420 kg/m³ for Plastic POM/Acetal.

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

Plastic POM/Acetal is stiffer: Young's modulus 2.8 GPa against 1.94 GPa for Plastic PETG, so the same part in Plastic POM/Acetal deflects less under the same load.

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

For the same stiffness or strength: Plastic POM/Acetal 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 PETG	Plastic POM/Acetal
Stiff rod or tie (tension)	29% heavier	lighter
Stiff beam (bending)	7% heavier	lighter
Stiff panel or plate	1% heavier	lighter
Strong rod or tie	34% heavier	lighter
Strong beam	17% heavier	lighter
Strong panel or plate	9% heavier	lighter

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 PETG or Plastic POM/Acetal?

Plastic POM/Acetal stretches further before it breaks: 75% elongation at break against 7.6% for Plastic PETG.

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

Plastic POM/Acetal conducts heat better: 0.4 W/m·K against 0.21 W/m·K for Plastic PETG.

Which expands less with temperature?

Plastic PETG expands less: 51 µm/m·K against 122 µm/m·K for Plastic POM/Acetal.

Among 59 materials

Stiffness against density

Strength against density