LDPE Properties | Mechanical, Thermal & Chemical Data

LDPE material properties are defined by a highly branched molecular structure that produces a relatively soft, low-density, flexible thermoplastic. Tensile strength runs 1,400–2,000 psi — considerably lower than HDPE or UHMW — but elongation at break exceeds 300%, and the material remains tough down to -100°F. The numbers below reflect standard virgin LDPE stock shapes; LLDPE grades vary slightly and are addressed on the grades comparison page.

At a Glance

• Density 0.92 g/cc — lowest of the standard polyethylene family
• Tensile strength 1,400–2,000 psi, elongation 300–500%
• Maximum continuous use temperature 160°F (71°C)
• Cold-temperature limit -100°F (-73°C) with maintained impact toughness
• Water absorption < 0.01% — dimensionally stable in wet environments
• Chemical resistance excellent against dilute acids, bases, and alcohols; poor against aromatics and chlorinated solvents
• FDA 21 CFR 177.1520 compliant in natural and white grades

Mechanical Properties

LDPE is not a structural material. Its strength figures are the lowest among commodity polyethylenes, and it creeps under sustained compressive or tensile loading. Within its envelope, however, it offers a unique combination of compliance and toughness that no stiffer material can replicate.

Tensile Behavior

LDPE yields at low stress and then extends dramatically before fracture. The stress-strain curve is characteristic: a low-slope elastic region, a clear yield point, followed by cold-drawing — the material necks and elongates at near-constant stress. This behavior makes LDPE forgiving in applications where deflection must be accommodated without fracture, such as flexible liner panels and gaskets cycling between sealed and unsealed positions.

Compressive and Creep Behavior

Compressive strength measured at 10% deformation is approximately 1,000–1,400 psi. Under sustained compressive load above 500 psi, LDPE creeps measurably. For shim and spacer applications, design bolt loads to keep compressive stress below 500 psi, or switch to HDPE, which offers roughly 3× the compressive strength. LDPE's creep rate increases with temperature — at 140°F, expect 20–40% more creep than at room temperature.

Hardness and Surface

Shore D 44–50 puts LDPE in the range of soft rubber compounds and firmly below HDPE (Shore D 60–70). The low hardness means LDPE conforms to mating surface irregularities under modest clamping loads — useful for gasket and seal applications — but also means the surface scratches and gouges easily. Abrasion resistance is moderate; LDPE outperforms many elastomers but significantly underperforms UHMW-PE in sliding wear.

Thermal Properties

Temperature Limits in Practice

The 160°F continuous-use rating is conservative — brief excursions to 175°F will not destroy a part, but sustained exposure at or above that temperature causes accelerated creep and permanent deformation. The 85–100°F HDT at 264 psi load is the more limiting design constraint for loaded parts in warm environments: room-temperature equipment sitting in direct summer sun can reach 130–160°F surface temperatures, which may soften an LDPE shim or gasket under load.

For wet steam (212°F), boiling water sterilization, or any continuous service above 160°F, upgrade to polypropylene (continuous to ~210°F) or HDPE (continuous to 180°F). A full comparison is in HDPE vs. LDPE.

Thermal Expansion

The CLTE of 11 × 10⁻⁵ in/in/°F is high relative to metals — about 5–6× that of steel and 3× that of aluminum. For LDPE parts assembled to metal frames, allow clearance for differential thermal movement. A 12-inch LDPE sheet spanning 100°F of temperature swing will expand or contract approximately 0.13 inches relative to a steel backing plate.

Low-Temperature Performance

At -100°F, LDPE remains tough and pliable. Crystalline content increases slightly at cryogenic temperatures, and stiffness rises, but the material does not become brittle. This distinguishes it from polypropylene, which embrittles below -4°F (−20°C), and from many elastomers that harden at cryogenic temperatures. LDPE is the preferred polyethylene for cryogenic liner and container applications.

Chemical Resistance

Chemical compatibility data below is for room temperature (73°F). Resistance always decreases at elevated temperature — run specific tests for process service above 120°F.

Effect of Concentration and Temperature

LDPE's resistance to dilute acids is notably better than its resistance to concentrated forms. Sulfuric acid below 30% at room temperature: excellent. Above 60% or above 120°F: the surface oxidizes and the material degrades. Run immersion coupons at actual service conditions for any acid service above 20% concentration.

Electrical Properties

LDPE is an excellent electrical insulator with very low dielectric loss, making it one of the preferred materials for RF and microwave cable dielectrics and insulating bushings.

The dielectric constant of 2.25–2.35 is among the lowest of any solid polymer, second only to PTFE. This makes LDPE useful in high-frequency applications where signal attenuation must be minimized. For antistatic requirements, carbon-black-filled black LDPE provides static dissipation — volume resistivity drops to approximately 10⁴–10⁶ Ω·cm depending on carbon content.

Physical Properties

Low water absorption (essentially zero) means LDPE parts do not swell, soften, or change dimension when exposed to water or humid environments. This is a key advantage for gaskets and liners operating in continuous wet service — unlike nylon or acetal, LDPE requires no size correction for moisture uptake.

Radiation exposure via gamma irradiation (common in medical device sterilization) causes LDPE to cross-link rather than degrade. Cross-linking increases density and reduces flexibility; high-dose irradiation (> 25 kGy) noticeably stiffens the material.

Comparing Properties to Adjacent Polyethylenes

LLDPE's improved tensile and puncture resistance make it a better choice where the liner or barrier must resist sharp edge penetration. For structural rigidity, neither LDPE nor LLDPE is competitive — HDPE or UHMW-PE are the correct materials once load-bearing enters the design criteria.

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