HDPE vs LDPE: Complete Comparison of High-Density and Low-Density Polyethylene
Published: February 11, 2026 | PailHQ Technical Team | 11 min read
HDPE and LDPE are two of the most widely used plastics in the world, yet they differ dramatically in structure, strength, flexibility, and application. Together, high-density polyethylene (HDPE) and low-density polyethylene (LDPE) account for over 36% of all plastic produced globally, with combined annual production exceeding 100 million metric tons. Understanding the difference between HDPE and LDPE is essential for selecting the right material for packaging, containers, bags, piping, and hundreds of other applications.
This guide provides a detailed technical comparison of HDPE vs LDPE covering molecular structure, mechanical and thermal properties, chemical resistance, recycling, cost, and practical guidance on which material to choose for specific uses.
Molecular Structure: Why HDPE and LDPE Behave Differently
Both HDPE and LDPE are polyethylene, meaning they are polymers made from the same ethylene monomer (C2H4). The critical difference lies in how the polymer chains are organized at the molecular level.
HDPE: Linear, Tightly Packed Chains
HDPE is produced using low-pressure polymerization with Ziegler-Natta or metallocene catalysts. The result is a polymer with minimal branching, allowing the chains to pack closely together in a highly crystalline structure.
- Chain branching: Very low (less than 7 branches per 1,000 carbon atoms)
- Crystallinity: 60-80%
- Density: 0.93-0.97 g/cm3
- Molecular weight: 200,000-500,000 g/mol
The tight molecular packing creates stronger intermolecular forces (Van der Waals forces), which translate directly into higher tensile strength, greater stiffness, and better chemical barrier properties.
LDPE: Branched, Loosely Packed Chains
LDPE is produced using high-pressure free radical polymerization, which generates significant long-chain and short-chain branching along the polymer backbone. These branches prevent the chains from packing tightly, resulting in a more amorphous structure.
- Chain branching: High (20-40 branches per 1,000 carbon atoms)
- Crystallinity: 40-55%
- Density: 0.91-0.94 g/cm3
- Molecular weight: 100,000-300,000 g/mol
The branched structure gives LDPE its characteristic flexibility and clarity but at the cost of reduced strength and lower chemical resistance compared to HDPE.
Property Comparison: HDPE vs LDPE Side by Side
The following table summarizes the key physical, mechanical, thermal, and chemical properties that differentiate HDPE from LDPE.
| Property | HDPE | LDPE |
|---|---|---|
| Density | 0.93-0.97 g/cm3 | 0.91-0.94 g/cm3 |
| Tensile Strength | 3,200-4,500 psi (22-31 MPa) | 1,500-2,500 psi (10-17 MPa) |
| Flexural Modulus | 145,000-225,000 psi | 25,000-50,000 psi |
| Elongation at Break | 100-1,000% | 100-650% |
| Impact Resistance | Excellent | Good |
| Hardness (Shore D) | 60-70 | 41-50 |
| Melting Point | 266 degrees F (130 degrees C) | 230 degrees F (110 degrees C) |
| Max Continuous Service Temp | 180 degrees F (82 degrees C) | 140 degrees F (60 degrees C) |
| Min Service Temp | -148 degrees F (-100 degrees C) | -58 degrees F (-50 degrees C) |
| Crystallinity | 60-80% | 40-55% |
| Transparency | Opaque to translucent | Translucent to semi-clear |
| UV Resistance | Good (with stabilizers) | Fair |
| Chemical Resistance | Excellent | Good |
| Water Absorption | 0.01% | 0.015% |
| Recycling Code | #2 | #4 |
| FDA Food Grade | Yes (21 CFR 177.1520) | Yes (21 CFR 177.1520) |
Strength and Rigidity
The difference between HDPE and LDPE is most apparent in their mechanical properties. HDPE is significantly stronger and more rigid, while LDPE is more flexible and pliable.
Tensile Strength
HDPE's tensile strength of 3,200-4,500 psi is roughly double that of LDPE at 1,500-2,500 psi. This means an HDPE container can support heavier loads with thinner walls. For 5-gallon pails, this translates to a bucket that holds 65-70 pounds of liquid without bulging or deforming, while an equivalent LDPE container would distort under the same load.
Stiffness (Flexural Modulus)
HDPE has a flexural modulus 3-9 times higher than LDPE, making it much stiffer. This stiffness is essential for stacking strength: HDPE pails can be stacked 3-4 high when filled without the bottom pail crushing. LDPE, with its lower stiffness, is unsuitable for rigid container applications where stacking and structural integrity are required.
Impact Resistance
Despite being stiffer, HDPE maintains excellent impact resistance, particularly at low temperatures. HDPE retains its toughness down to -148 degrees Fahrenheit, while LDPE becomes brittle below -58 degrees Fahrenheit. This makes HDPE the preferred material for containers stored in freezers, cold warehouses, or outdoor winter environments.
Temperature Performance
Both materials perform well across a range of temperatures, but HDPE offers a significantly wider operational window.
Heat Resistance
HDPE withstands continuous exposure up to 180 degrees Fahrenheit compared to LDPE's limit of 140 degrees Fahrenheit. For applications like hot-fill food packaging, chemical containers that may be stored in hot warehouses, or automotive products exposed to engine heat, HDPE provides a meaningful safety margin.
Cold Performance
HDPE's cold temperature performance is where the difference is most dramatic. HDPE maintains impact resistance down to -148 degrees Fahrenheit, making it suitable for deep freeze storage and Arctic conditions. LDPE, while adequate for standard freezer temperatures (0 to -20 degrees Fahrenheit), becomes increasingly brittle at extreme cold.
Chemical Resistance
HDPE offers broader and more robust chemical resistance than LDPE, a direct consequence of its tighter molecular packing and higher crystallinity.
Where HDPE Outperforms LDPE
- Strong acids and bases: HDPE resists concentrated sulfuric acid (70%), hydrochloric acid (37%), and sodium hydroxide (50%) with no degradation. LDPE shows swelling and softening with prolonged exposure to the same chemicals.
- Oxidizers: HDPE handles hydrogen peroxide (30%) and sodium hypochlorite (12.5%) without issue. LDPE is more susceptible to oxidative degradation.
- Solvents: While neither material resists aromatic solvents well, HDPE shows less swelling and weight gain than LDPE when exposed to mild organic solvents.
- Stress crack resistance: HDPE formulated for containers achieves ESCR ratings exceeding 1,000 hours per ASTM D1693, while LDPE is more vulnerable to environmental stress cracking when exposed to surfactants and detergents.
Where Performance Is Comparable
Both HDPE and LDPE perform well with:
- Water and aqueous solutions
- Alcohols (methanol, ethanol, isopropanol)
- Common salt solutions
- Most food products (oils, vinegar, syrups, dairy)
Key Takeaway for Chemical Storage
If you are storing any chemical beyond basic household products, HDPE is the safer and more durable choice. This is why industrial 5-gallon pails, chemical drums, and UN-certified hazmat containers are manufactured almost exclusively from HDPE rather than LDPE.
Applications: Where Each Material Excels
The different properties of HDPE and LDPE lead to distinct application profiles.
Common HDPE Applications
- 5-gallon pails and buckets: The standard material for industrial, food-grade, and hazmat containers
- Milk jugs and juice bottles: Rigid, food-safe, and cost-effective
- Detergent and chemical containers: Excellent chemical resistance and stacking strength
- Cutting boards: FDA-approved, durable, and easy to sanitize
- Piping (water and gas): Corrosion-proof with a 50-100 year service life
- Playground equipment: Impact-resistant and weather-durable
- Lumber alternatives (composite decking): Made from recycled HDPE
- Geomembranes: Landfill liners and containment barriers
- Automotive fuel tanks: Chemical resistance and impact performance
Common LDPE Applications
- Plastic bags (grocery, produce, zipper bags): Flexibility and clarity
- Shrink wrap and stretch film: Clings and conforms to irregularly shaped objects
- Squeeze bottles: Flexibility allows easy dispensing
- Trash can liners: Flexible, puncture-resistant film
- Food wrap and sandwich bags: Flexibility and food safety
- Agricultural film (mulch film, greenhouse covers): UV-stabilized LDPE film
- Wire and cable insulation: Excellent electrical insulation properties
- Coatings (paper cups, cartons): Moisture barrier layer
Summary
HDPE is the material of choice when rigidity, strength, and chemical resistance are priorities. LDPE excels where flexibility, transparency, and film-forming ability are more important than structural strength.
Recycling: HDPE (#2) vs LDPE (#4)
Recycling infrastructure and rates differ significantly between HDPE and LDPE, which is an important consideration for both environmental sustainability and regulatory compliance.
HDPE Recycling (Resin Code #2)
- Curbside acceptance: Over 95% of U.S. curbside programs accept HDPE containers
- Recycling rate: Approximately 30% of HDPE containers are recycled in the United States
- Recycled products: Drainage pipe, plastic lumber, playground equipment, new bottles and containers
- Processing: Mechanical recycling (shredding, washing, remelting) is well established
- Value: HDPE is one of the highest-value post-consumer plastics, with recycled resin prices ranging from $0.15-$0.35 per pound
LDPE Recycling (Resin Code #4)
- Curbside acceptance: Limited; only about 30% of U.S. curbside programs accept LDPE
- Recycling rate: Less than 5% of LDPE film is recycled in the United States
- Drop-off programs: Many grocery stores and retailers accept LDPE bags and film for recycling through store drop-off programs
- Recycled products: Composite lumber, trash can liners, shipping envelopes, new bags
- Processing challenges: LDPE film tends to jam sorting equipment at recycling facilities, which is why many programs exclude it from curbside collection
Environmental Impact
HDPE's higher recycling rate and broader curbside acceptance make it the more environmentally responsible choice when end-of-life management is a consideration. The American Chemistry Council reports that HDPE container recycling has increased by 18% over the past decade, driven by improved collection infrastructure and growing demand for recycled HDPE resin.
LDPE recycling remains challenging due to the difficulty of collecting and sorting flexible film. However, chemical recycling (pyrolysis) technologies are emerging that can process mixed LDPE film into feedstock for new plastic production, with several commercial-scale plants expected to come online by 2027.
Cost Comparison
Both HDPE and LDPE are commodity plastics with competitive pricing, though costs fluctuate based on petroleum prices, demand, and regional supply.
Resin Pricing (Approximate)
- HDPE resin: $0.55-$0.85 per pound (commodity grade)
- LDPE resin: $0.60-$0.90 per pound (commodity grade)
Processing Costs
- HDPE containers (injection/blow molding): Higher tooling investment but faster cycle times and lower per-unit cost at scale
- LDPE film (blown film extrusion): Lower tooling investment but higher per-unit material usage for equivalent barrier performance
Total Cost of Ownership
For container applications, HDPE is typically more cost-effective because its higher strength allows thinner walls, reducing material usage per container. A standard 5-gallon HDPE pail uses approximately 1.5-2.0 pounds of resin, while an equivalent LDPE container (if it could maintain structural integrity) would require significantly more material to achieve the same stacking strength and load capacity.
How to Choose Between HDPE and LDPE
Choose HDPE When You Need:
- Rigid containers (pails, buckets, bottles, drums)
- Structural strength and stacking capability
- Broad chemical resistance for industrial or hazardous contents
- High-temperature performance (up to 180 degrees Fahrenheit)
- Extreme cold performance (down to -148 degrees Fahrenheit)
- UN-certified hazmat packaging
- Maximum recyclability through curbside programs
- FDA food-grade containers for long-term storage
Choose LDPE When You Need:
- Flexible packaging (bags, wraps, pouches, film)
- Squeeze bottles or containers that need to deform during use
- Transparency or translucency in the finished product
- Wire insulation or cable jacketing
- Moisture barrier coatings on paper or cardboard
- Agricultural film for mulching, greenhouse covers, or silage wrap
- Low-cost disposable packaging for single-use applications
When Either Material Works
For applications like simple lids, caps, or non-structural components where neither extreme strength nor extreme flexibility is required, either material can work. In these cases, the decision often comes down to processing compatibility, available tooling, and supply chain preferences.
Frequently Asked Questions
Is HDPE stronger than LDPE?
Yes. HDPE has roughly twice the tensile strength of LDPE (3,200-4,500 psi vs 1,500-2,500 psi) and a flexural modulus 3-9 times higher. This makes HDPE significantly more rigid and better suited for structural applications like containers, pails, and piping. LDPE's lower strength is offset by its greater flexibility, which makes it ideal for bags, films, and squeeze bottles.
Can LDPE be used for 5-gallon buckets?
LDPE is not suitable for standard 5-gallon bucket construction. Its lower tensile strength and flexural modulus mean an LDPE bucket would bulge, deform, and potentially fail when filled with heavy contents. LDPE also cannot achieve the stacking strength required for palletized storage and shipping. HDPE is the universal standard for 5-gallon pails and buckets because of its superior rigidity, impact resistance, and chemical compatibility.
Is HDPE or LDPE easier to recycle?
HDPE is significantly easier to recycle. Over 95% of U.S. curbside recycling programs accept HDPE containers (recycling code #2), and the material has a recycling rate of approximately 30%. LDPE (recycling code #4) is accepted by fewer than 30% of curbside programs, with a recycling rate below 5% for film products. LDPE bags and film can be recycled through store drop-off programs at many grocery retailers.
Are HDPE and LDPE both food safe?
Yes, both HDPE and LDPE are FDA-approved for food-contact applications under 21 CFR 177.1520, provided they are manufactured with food-grade resins and approved additives. Both materials are inherently BPA-free. The choice between them for food applications depends on the container format: HDPE for rigid containers, bottles, and cutting boards; LDPE for food wrap, bags, and squeeze bottles.
What is the difference between HDPE and LDPE recycling numbers?
HDPE is identified by recycling code #2 and LDPE by recycling code #4 under the Resin Identification Code system established by the Society of the Plastics Industry (now the Plastics Industry Association). These numbers indicate the type of plastic resin, not recyclability, though in practice HDPE (#2) is far more widely recycled than LDPE (#4) due to collection infrastructure and processing compatibility.
HDPE 5-Gallon Pails From PailHQ
PailHQ supplies industrial-grade HDPE 5-gallon pails for food processing, chemical storage, agricultural, and general-purpose applications. Our M2 series pails are manufactured from virgin HDPE resin with 90-mil wall thickness, gasket lids, and full regulatory documentation including FDA food-grade and UN 1H2/Y27/S hazmat certifications.
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