Plastic Polypropylene vs. DMLS 316L Stainless Steel

Compare Plastic Polypropylene vs. DMLS 316L Stainless Steel strength, stiffness, weight and thermal properties.

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Plastic PolypropyleneBulk polymer (molded or machined)

DMLS 316L Stainless Steel3D printed metal (DMLS)

Mechanical
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Yield strength	33MPasourcetypical, tensile stress at yield ISO 527	530MPasourcetypical, as manufactured, horizontal
Ultimate tensile strength	not sourced	640MPasourcetypical, as manufactured, horizontal
Elongation at break	not sourced	40%sourcetypical at break, as manufactured, horizontal
Young's modulus (stiffness)	1.45GPasourcetypical, tensile modulus ISO 527	185GPasourcetypical, as built, horizontal (XY); EOSINT M280-400W / M290-400W, 316L_Surface 1.0, 20 µm (2014 sheet)
Density	900kg/m³sourcetypical, 23 °C ISO 1183-1	7,900kg/m³sourcepart density (ISO 3369, not labelled min or typical), EOS M 290, 40 µm FlexLine
Strength to weight	36.7kN·m/kg	67.1kN·m/kg1.83x higher
Stiffness to weight	1.61MN·m/kg	23.4MN·m/kg14.5x higher
Poisson's ratio	0.42sourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	0.3sourcebase material: austenitic stainless steels incl. 1.4404 (316L), design value
Shear modulus	0.511GPa	71.2GPa139x stiffer in shear
Bulk modulus	3.02GPa	154GPa
Speed of sound	1,269m/s	4,839m/s
Thermal
Thermal conductivity	0.17–0.22W/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	16.2W/m·Ksourcebase material: wrought 316/316L (Cleveland-Cliffs), at 100 °C
Thermal expansion	80–100µm/m·Ksourcebase material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)	15.7µm/m·Ksourcemean 25-100 °C, ASTM E228
100 mm part over a 50 °C swing	450µm growth	78.6µm growth5.73x less
Specific heat	not sourced	500J/kg·Ksourcebase material: wrought 316/316L (Cleveland-Cliffs), 0-100 °C
Heats up and cools (diffusivity)	not sourced	4.1mm²/s
Thermal shock resistance	28.6W/m	2,067W/m72.3x more resistant
Max service temperature	90°CsourceHDT 0.45 MPa (ISO 75B), unannealed	not sourced
Values for	LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values	EOS StainlessSteel 316L (powder 9011-0032), EOS M 290, ParameterSet 316L 20µm Surface M290/400W, as manufactured, horizontal; ISO 6892-1

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.

DMLS 316L Stainless Steel is 3D printed: its properties depend on build direction and print settings; these are typical values.

Questions

Is Plastic Polypropylene stronger than DMLS 316L Stainless Steel?

DMLS 316L Stainless Steel is stronger: its yield strength is 530 MPa against 33 MPa for Plastic Polypropylene (16.1x).

Which is lighter, Plastic Polypropylene or DMLS 316L Stainless Steel?

Plastic Polypropylene is lighter: 900 kg/m³ against 7,900 kg/m³ for DMLS 316L Stainless Steel.

Which is stiffer, Plastic Polypropylene or DMLS 316L Stainless Steel?

DMLS 316L Stainless Steel is stiffer: Young's modulus 185 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in DMLS 316L Stainless Steel deflects less under the same load.

Which is lighter for the same job, Plastic Polypropylene or DMLS 316L Stainless Steel?

For the same stiffness or strength: Plastic Polypropylene is lighter for a stiff panel or plate, strong beam, strong panel or plate; DMLS 316L Stainless Steel is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.

Part that must be	Plastic Polypropylene	DMLS 316L Stainless Steel
Stiff rod or tie (tension)	14.5x heavier	lighter
Stiff beam (bending)	29% heavier	lighter
Stiff panel or plate	lighter	1.74x heavier
Strong rod or tie	1.83x heavier	lighter
Strong beam	lighter	38% heavier
Strong panel or plate	lighter	2.19x 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 Polypropylene or DMLS 316L Stainless Steel?

DMLS 316L Stainless Steel conducts heat better: 16.2 W/m·K against 0.195 W/m·K for Plastic Polypropylene.

Which expands less with temperature?

DMLS 316L Stainless Steel expands less: 15.7 µm/m·K against 90 µm/m·K for Plastic Polypropylene.

Among 59 materials

Stiffness against density

Strength against density