Plastic Polypropylene vs. SLA Resin Standard

Compare Plastic Polypropylene vs. SLA Resin Standard strength, stiffness, weight and thermal properties.

Plastic PolypropyleneBulk polymer (molded or machined)

SLA Resin Standard3D printed (SLA resin)

Mechanical	Plastic Polypropylene	SLA Resin Standard
Yield strength	33MPa1	not given (tensile used)
Ultimate tensile strength	not stated (yield given)	60MPa2
Flexural strength	not sourced	105MPa2
Elongation at break	not sourced	8%2
Young's modulus (stiffness)	1.45GPa1	2.75GPa21.9x stiffer
Density	900kg/m³134% lighter	1,210kg/m³3
Strength to weight	36.7kN·m/kg	49.6kN·m/kg35% higher
Stiffness to weight	1.61MN·m/kg	2.27MN·m/kg41% higher
Poisson's ratio	base material0.424	not sourced
Shear modulus	0.511GPa	not sourced
Bulk modulus	3.02GPa	not sourced
Speed of sound	1,269m/s	1,508m/s19% faster

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Plastic Polypropylene	SLA Resin Standard
Thermal conductivity	base material0.17–0.22W/m·K4	0.54W/m·K5
Thermal expansion	base material80–100µm/m·K4	mean -30 to 140 °C114µm/m·K5
100 mm part over a 50 °C swing	450µm growth27% less	571µm growth
Specific heat	not sourced	1,800J/kg·K5
Heats up and cools (diffusivity)	not sourced	0.248mm²/s
Thermal shock resistance	28.6W/m	not sourced
Max service temperature	HDT 0.45 MPa90°C1	HDT 1.8 MPa59°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: LyondellBasell, Formlabs, INEOS Olefins & Polymers USA

Plastic Polypropylene: LyondellBasell Moplen HP501H polypropylene homopolymer (general purpose), typical ISO values
SLA Resin Standard: Formlabs Clear Resin V5 (FLGPCL05), TDS Rev. 01 March 20, 2024; printed on Form 4 at 100 µm, washed 5 min in >=99% IPA, post-cured 15 min at 60 °C in Form Cure. Orientation not stated.

1
Moplen HP501H Product DataLyondellBasellPlastic Polypropylene · Yield strength: typical, tensile stress at yield ISO 527Plastic Polypropylene · Young's modulus (stiffness): typical, tensile modulus ISO 527Plastic Polypropylene · Density: typical, 23 °C ISO 1183-1Plastic Polypropylene · Max service temperature: HDT 0.45 MPa (ISO 75B), unannealed
2
Clear Resin V5 Technical Data Sheet (2024)Formlabsarchived copySLA Resin Standard · Ultimate tensile strength: typicalSLA Resin Standard · Flexural strength: typicalSLA Resin Standard · Elongation at break: typicalSLA Resin Standard · Young's modulus (stiffness): typicalSLA Resin Standard · Max service temperature: HDT 1.8 MPa
3
Clear Resin V5 Technical Data Sheet (web edition)FormlabsSLA Resin Standard · Density: typical, post-cured (same for 5 min ambient and 15 min at 60 °C), ASTM D792
4
Typical Engineering Properties of PolypropyleneINEOS Olefins & Polymers USAarchived copyPlastic Polypropylene · Poisson's ratio: base material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)Plastic Polypropylene · Thermal conductivity: base material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)Plastic Polypropylene · Thermal expansion: base material: polypropylene homopolymer family (INEOS Olefins & Polymers USA, Typical Engineering Properties of Polypropylene)
5
Thermal Properties of Selected Formlabs SLA ResinsFormlabsSLA Resin Standard · Thermal conductivity: typical, post-cured, ASTM E1530SLA Resin Standard · Thermal expansion: mean -30 to 140 °C, post-cured (5 min ambient cure), TMA ASTM E831SLA Resin Standard · Specific heat: typical, 25 °C, post-cured (5 min ambient cure), DSC ASTM E1269

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.

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

Questions

Mechanical

Is Plastic Polypropylene stronger than SLA Resin Standard?

SLA Resin Standard is stronger: its tensile strength is 60 MPa against yield strength 33 MPa for Plastic Polypropylene (1.82x).

Which is lighter, Plastic Polypropylene or SLA Resin Standard?

Plastic Polypropylene is lighter: 900 kg/m³ against 1,210 kg/m³ for SLA Resin Standard.

Which is stiffer, Plastic Polypropylene or SLA Resin Standard?

SLA Resin Standard is stiffer: Young's modulus 2.75 GPa against 1.45 GPa for Plastic Polypropylene, so the same part in SLA Resin Standard deflects less under the same load.

Which is lighter for the same job, Plastic Polypropylene or SLA Resin Standard?

For the same stiffness or strength: Plastic Polypropylene is lighter for a stiff panel or plate; SLA Resin Standard is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie, strong beam.

Part that must be	Plastic Polypropylene	SLA Resin Standard
Stiff rod or tie (tension)	41% heavier	lighter
Stiff beam (bending)	2% heavier	lighter
Stiff panel or plate	lighter	9% heavier
Strong rod or tie	35% heavier	lighter
Strong beam	11% heavier	lighter
Strong panel or plate	about equal	about equal

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).

Thermal

Which conducts heat better, Plastic Polypropylene or SLA Resin Standard?

SLA Resin Standard conducts heat better: 0.54 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 114 µm/m·K for SLA Resin Standard.