Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources3 documents: LyondellBasell, Röhm, INEOS Olefins & Polymers USA
Plastic HDPE
LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values
Plastic PMMA
Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1)
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Hostalen 23050 B Product DataLyondellBasellPlastic HDPE · Yield strength: typical, tensile stress at yield 23 °C, 50 mm/min ISO 527Plastic HDPE · Young's modulus (stiffness): typical, tensile modulus 23 °C ISO 527Plastic HDPE · Density: typical, ISO 1183
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PLEXIGLAS GS and XT Technical Information (Ref. No. 211-1)Röhmarchived copyPlastic PMMA · Ultimate tensile strength: typical, 23 °CPlastic PMMA · Compressive strength: compressive yield stress, typicalPlastic PMMA · Flexural strength: typicalPlastic PMMA · Elongation at break: typicalPlastic PMMA · Young's modulus (stiffness): typical, short-termPlastic PMMA · Density: typicalPlastic PMMA · Poisson's ratio: typicalPlastic PMMA · Thermal conductivity: typicalPlastic PMMA · Thermal expansion: 0-50 °CPlastic PMMA · Specific heat: typicalPlastic PMMA · Max service temperature: max. permanent service temperature
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Typical Engineering Properties of High Density PolyethyleneINEOS Olefins & Polymers USAarchived copyPlastic HDPE · Poisson's ratio: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal conductivity: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Thermal expansion: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)Plastic HDPE · Specific heat: base material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE)
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 HDPE stronger than Plastic PMMA?
Plastic PMMA is stronger: its tensile strength is 80 MPa against yield strength 24 MPa for Plastic HDPE (3.33x).
Which is lighter, Plastic HDPE or Plastic PMMA?
Plastic HDPE is lighter: 950 kg/m³ against 1,190 kg/m³ for Plastic PMMA.
Which is stiffer, Plastic HDPE or Plastic PMMA?
Plastic PMMA is stiffer: Young's modulus 3.3 GPa against 0.9 GPa for Plastic HDPE, so the same part in Plastic PMMA deflects less under the same load.
Which is lighter for the same job, Plastic HDPE or Plastic PMMA?
For the same stiffness or strength: Plastic PMMA 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 HDPE
Plastic PMMA
Stiff rod or tie (tension)
2.93x heavier
lighter
Stiff beam (bending)
1.53x heavier
lighter
Stiff panel or plate
23% heavier
lighter
Strong rod or tie
2.66x heavier
lighter
Strong beam
1.78x heavier
lighter
Strong panel or plate
46% 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).
Thermal
Which conducts heat better, Plastic HDPE or Plastic PMMA?
Plastic HDPE conducts heat better: 0.445 W/m·K against 0.19 W/m·K for Plastic PMMA.
Which expands less with temperature?
Plastic PMMA expands less: 70 µm/m·K against 120 µm/m·K for Plastic HDPE.